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Slide 2: Praise for The iPhone Developer’s Cookbook “This book would be a bargain at ten times its price! If you are writing iPhone software, it will save you weeks of development time. Erica has included dozens of crisp and clear examples illustrating essential iPhone development techniques and many others that show special effects going way beyond Apple’s official documentation.” —Tim Burks, iPhone Software Developer,TootSweet Software “Erica Sadun’s technical expertise lives up to the Addison-Wesley name. The iPhone Developer’s Cookbook is a comprehensive walkthrough of iPhone development that will help anyone out, from beginners to more experienced developers. Code samples and screenshots help punctuate the numerous tips and tricks in this book.” —Jacqui Cheng, Associate Editor, Ars Technica “We make our living writing this stuff and yet I am humbled by Erica’s command of her subject matter and the way she presents the material: pleasantly informal, then very appropriately detailed technically.This is a going to be the Petzold book for iPhone developers.” —Daniel Pasco, Lead Developer and CEO, Black Pixel Luminance “The iPhone Developer’s Cookbook: Building Applications with the iPhone SDK should be the first resource for the beginning iPhone programmer, and is the best supplemental material to Apple’s own documentation.” —Alex C. Schaefer, Lead Programmer, ApolloIM, iPhone Application Development Specialist, MeLLmo, Inc “Erica’s book is a truly great resource for Cocoa Touch developers.This book goes far beyond the documentation on Apple’s Web site, and she includes methods that give the developer a deeper understanding of the iPhone OS, by letting them glimpse at what’s going on behind the scenes on this incredible mobile platform.” —John Zorko, Sr. Software Engineer, Mobile Devices
Slide 4: The iPhone™ Developer’s Cookbook
Slide 6: The iPhone™ Developer’s Cookbook Building Applications with the iPhone SDK Erica Sadun Upper Saddle River, NJ • Boston • Indianapolis • San Francisco New York • Toronto • Montreal • London • Munich • Paris • Madrid Cape Town • Sydney • Tokyo • Singapore • Mexico City
Slide 7: Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed with initial capital letters or in all capitals. The author and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of the use of the information or programs contained herein. The publisher offers excellent discounts on this book when ordered in quantity for bulk purchases or special sales, which may include electronic versions and/or custom covers and content particular to your business, training goals, marketing focus, and branding interests. For more information, please contact: U.S. Corporate and Government Sales (800) 382-3419 corpsales@pearsontechgroup.com For sales outside the United States please contact: International Sales international@pearsoned.com AirPort, Apple, the Apple logo, Aqua, Bonjour, Cocoa, Cover Flow, Dashcode, Finder, FireWire, iMac, iPhone, iPod, iTunes, the iTunes logo, Mac, Mac logo, Macintosh, Multi-Touch, Objective-C, QuickTime, QuickTime logo, Safari, Spotlight, and Xcode are trademarks of Apple, Inc., registered in the U.S. and other countries. Visit us on the Web: informit.com/aw Editor-in-Chief Karen Gettman Senior Acquisitions Editor Chuck Toporek Senior Development Editor Chris Zahn Managing Editor Kristy Hart Project Editor Chelsey Marti Copy Editor Keith Cline Indexers Cheryl Lenser, Erika Millen Proofreader San Dee Phillips Technical Reviewers Tim Burks, Daniel Pasco, Alex C. Schaefer Publishing Coordinator Romny French Cover Designer Gary Adair Composition Nonie Ratcliff Library of Congress Cataloging-in-Publication Data: Sadun, Erica. The iPhone developer’s cookbook : building mobile applications with the iPhone SDK / Erica Sadun. p. cm. ISBN-10: 0-321-55545-7 (pbk. : alk. paper) ISBN-13: 978-0-321-55545-8 (pbk. : alk. paper) 1. iPhone (Smartphone)– Programming. 2. Computer software–Development. 3. Mobile computing. I. Title. QA76.8.I64S33 2009 005.26—dc22 2008030294 Copyright © 2009 Pearson Education, Inc. All rights reserved. Printed in the United States of America. This publication is protected by copyright, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permissions, write to: Pearson Education, Inc Rights and Contracts Department 501 Boylston Street, Suite 900 Boston, MA 02116 Fax (617) 671 3447 ISBN-13: 978-0-321-55545-8 ISBN-10: 0-321-55545-7 Text printed in the United States on recycled paper at RR Donnelley in Crawfordsville, Indiana. First printing October 2008
Slide 8: ❖ I dedicate this book with love to my husband, Alberto, who has put up with too many gadgets and too many SDKs over the years while remaining both kind and patient at the end of the day. ❖
Slide 10: Contents Preface xvii xxi xxii 1 2 4 4 Acknowledgments About the Author 1 Introducing the iPhone SDK Apple’s iPhone SDK 1 Assembling iPhone Projects iPhone Application Components Application Folder Hierarchy The Executable The Info.plist File XIB (NIB) files Sandboxes 7 8 8 8 9 9 10 11 8 9 6 4 4 The Icon and Default Images 6 7 Files Not Found in the Application Bundle Platform Limitations Storage Limits Memory Limits Interaction Limits Energy Limits Application Limits SDK Limitations 10 11 18 Data Access Limits User Behavior Limits Programming Paradigms Model-View-Controller Object-Oriented Programming 11 19 Building an iPhone Application Skeleton The Hello World Application The Classes The Code 20 19 A Note About Sample Code and Memory Management 20
Slide 11: x Contents Building Hello World 23 23 24 25 28 24 Create an iPhone Project Running the Skeleton Customize the iPhone Project Using the Debugger Development Phones Application Identifiers 26 28 29 Editing Identification Information Apple’s iPhone Developer Program From Xcode to Your iPhone: The Organizer Interface Projects and Sources List Devices List Summary Tab Console Tab Crash Logs Tab Screenshot Tab About Tethering 31 31 31 31 32 32 32 33 34 30 30 Testing Applications on Your iPhone Compiling for Distribution Using Undocumented API Calls Ad Hoc Distribution Summary 36 35 2 Views 37 37 39 42 37 42 44 45 48 51 53 54 UIView and UIWindow Hierarchy Gestures Reorienting UITouch 46 Geometry and Traits Recipe: Adding Stepwise Subviews Recipe: Dragging Views Adding Persistence Recipe: Clipped Views Balancing Touches with Clipping Accessing Pixel-by-Pixel Values
Slide 12: Contents xi Recipe: Detecting Multitouch UIView Animations 59 56 59 Building UIView Animation Blocks Recipe: Fading a View In and Out Recipe: Swapping Views Recipe: Flipping Views 62 64 60 Recipe: Applying CATransitions to Layers Undocumented Animation Types General Core Animation Calls Recipe: Swiping Views 69 72 74 Recipe: Transforming Views Summary 74 67 68 66 Centering Landscape Views 3 View Controllers View Management Core Classes 77 77 77 78 79 Specialized Classes Creating a UIViewController Working with Interface Builder to Build Views for UIViewControllers 81 Temperature Conversion Example Loading XIB Files Directly Navigation Controllers 91 91 92 93 97 100 90 81 Setting Up a Navigation Controller The Navigation Item Class 92 Pushing and Popping View Controllers Recipe: Building a Simple Two-Item Menu Recipe: Adding a Segmented Control 95 Recipe: Adding a UIToolbar to a Navigation Bar Recipe: Navigating Between View Controllers Popping Back to the Root Tab Bars Summary 103 106 102 102 Loading a View Controller Array
Slide 13: xii Contents 4 Alerting Users 107 107 108 110 110 113 117 112 115 Talking Directly to Your User Through Alerts Logging Your Results Building Alerts 109 Displaying the Alert Recipe: Creating Multiline Button Displays Recipe: Autotimed No-Button Alerts Recipe: Presenting Simple Menus Recipe: Soliciting Text Input from the User “Please Wait”: Showing Progress to Your User Recipe: Invoking the Basic Undocumented UIProgressHUD 117 Recipe: Using UIActivityIndicatorView Recipe: Building a UIProgressView Recipe: Building a Scroll-Down Alert Recipe: Adding Status Bar Images Adding Application Badges Recipe: Simple Audio Alerts Vibration Summary 136 136 132 134 119 121 Recipe: Adding Custom, Tappable Overlays 127 131 123 5 Basic Tables 139 139 140 141 142 Introducing UITableView and UITableViewController Creating the Table What the UITableViewController Does Recipe: Creating a Simple List Table Data Source Functions Reusing Cells 143 143 Font Table Sample 142 Recipe: Creating a Table-Based Selection Sheet Recipe: Loading Images into Table Cells Recipe: Setting a Cell’s Text Traits Removing Cell Selections 152 153 155 Recipe: Creating Complex Cells 151 149 145 Recipe: Creating Checked Selections
Slide 14: Contents xiii Recipe: Deleting Cells 157 157 158 158 Creating and Displaying Remove Controls Dismissing Remove Controls Handling Delete Requests Swiping Cells Adding Cells 158 159 161 162 Recipe: Reordering Cells Summary 164 Recipe: Working with Disclosures 6 Advanced Tables 165 165 166 171 Recipe: Grouping Table Selections Adding Section Headers 170 Building a Section-Based Data Source Recipe: Building a Section Table with an Index Recipe: Custom Cell Backgrounds Customizing the Table View Recipe: Framing Tables 179 180 182 172 176 Recipe: Creating Alternate Blue and White Cells Recipe: Adding Coupled Cell Controls Recipe: Building a Multiwheel Table Creating the UIPickerView Recipe: Using the UIDatePicker Creating the Date Picker 183 186 186 177 Recipe: Creating Fully Customized Group Tables Creating Grouped Preferences Tables Summary 195 189 189 7 Media 197 Recipe: Browsing the Documents Folder by File Type 197 Locating Documents 198 200 201 203 205 Loading and Viewing Images Recipe: Displaying Small Images Recipe: Using a UIWebView to Display Images Displaying Web Pages with UIWebView Recipe: Browsing Your Image Library 206
Slide 15: xiv Contents Recipe: Selecting and Customizing Images from the Camera Roll 209 Recipe: Snapping Pictures with the iPhone Camera Working with iPhone Audio 214 215 Recipe: Playing Audio with Celestial 212 Recipe: Using the Media Player for Audio and Video Playback 217 Recipe: Recording Audio Reading in Text Data 219 227 228 227 Displaying Property Lists Summary 229 Recovering Media from Backup Files 8 Controls 231 231 232 233 236 Recipe: Building Simple Buttons The UIButton class Glass Buttons 236 Building Custom Buttons Recipe: Adding Animated Elements to Buttons Recipe: Animating Button Responses Recipe: Customizing Switches 239 241 242 Customizing UIAlertView Buttons Recipe: Adding Custom Slider Thumbs Adding Text to the Slider 246 238 Recipe: Dismissing a UITextField Keyboard Recipe: Dismissing UITextView Keyboards Recipe: Adding an Undo Button to Text Views Recipe: Building an Interactive Search Bar Recipe: Adding Callout Views Adding a Page Indicator Control Recipe: Customizing Toolbars Toolbar Tips Summary 267 266 258 260 263 246 248 250 253 Recipe: Creating a Text View–Based HTML Editor 255 9 People, Places, and Things Address Book Frameworks Address Book UI Address Book 269 270 269 269
Slide 16: Contents xv Recipe: Accessing Address Book Image Data Recipe: Displaying Address Book Information Recipe: Browsing the Address Book Adding New Contacts Core Location 278 278 280 277 274 277 Browsing for (Only) E-Mail Addresses 271 273 How Core Location Works Recipe: Core Location in a Nutshell Recipe: Reverse Geocoding to an Address Recipe: Accessing Core Device Information Recipe: Enabling and Disabling the Proximity Sensor 289 Recipe: Using Acceleration to Locate “Up” 283 286 288 Recipe: Accessing Maps Using Core Location Data 290 Recipe: Using Acceleration to Move Onscreen Objects 292 Summary 295 10 Connecting to Services 297 297 297 Recipe: Adding Custom Settings Bundles Declaring Application Settings Recipe: Subscribing Applications to Custom URL Schemes 302 Recipe: Checking Your Network Status Testing the Network Status Querying Site IP Addresses Checking Site Availability 304 305 306 307 308 313 311 318 Recovering a Local IP Address 304 Recipe: Interacting with iPhone Databases Recipe: Converting XML into Trees Storing Multiple Keychain Values Keychain Persistence 319 320 Sending and Receiving Files Push Notifications Summary 326 325 Recipe: Storing and Retrieving Keychain Items Recipe: Building a Simple Web-Based Server 321
Slide 17: xvi Contents 11 One More Thing: Programming Cover Flow The UICoverFlowLayer Class Building a Cover Flow View 327 329 331 332 327 Building a Cover Flow View Controller Cover Flow Data Source Methods Cover Flow Delegate Methods Summary 336 333 Index 357
Slide 18: Preface Few platforms match the iPhone’s unique developer technologies. It combines OS X-based mobile computing with an innovative multitouch screen, location awareness, an onboard accelerometer, and more.When Apple introduced the iPhone Cocoa Touch SDK beta in early March 2008, developers responded in numbers that brought Apple’s servers to its knees. Apple delivered more than one hundred thousand SDK downloads in less than one week.The iPhone Developer’s Cookbook was written to address this demand, providing an accessible resource for those new to iPhone programming. Who This Book Is For This book is written for new iPhone developers with projects to get done and a new unfamiliar SDK in their hands. Although each programmer brings different goals and experiences to the table, most developers end up solving similar tasks in their development work: “How do I build a table?”; “How do I create a secure keychain entry?”; “How do I search the Address Book?”; “How do I move between views?”; and “How do I use Core Location?” The iPhone Developer’s Cookbook is aimed squarely at anyone just getting started with iPhone programming.With its clear, fully documented examples, it will get you up to speed and working productively. It presents already tested ready-to-use solutions, letting programmers focus on the specifics of their application rather than on boilerplate tasks. How This Book Is Structured This book offers single-task recipes for the most common issues new iPhone developers face: laying out interface elements, responding to users, accessing local data sources, and connecting to the Internet.The cookbook approach delivers cut-and-paste convenience. Programmers can add source recipes into their projects and then customize them to their needs. Each chapter groups related tasks together. Readers can jump directly to the kind of solution they’re looking for without having to decide which class or framework best matches that problem. Here’s a rundown of what you’ll find in this book’s chapters: n Chapter 1: Getting Started with the iPhone SDK Chapter 1 introduces the iPhone SDK and explores the iPhone as a delivery platform, limitations and all. It explains the breakdown of the standard iPhone application and enables you to build your first Hello World style samples.
Slide 19: xviii Preface n n n Chapter 2: Views Chapter 2 introduces iPhone views, objects that live on your screen.You see how to lay out, create, and order your views to create backbones for your iPhone applications.You read about view hierarchies, geometries, and animations as well as how users can interact with views through touch. Chapter 3: View Controllers The iPhone paradigm in a nutshell is this: small screen, big virtual worlds. In Chapter 3, you discover the various UIViewController classes that enable you to enlarge and order the virtual spaces your users interact with.You learn how to let these powerful objects perform all the heavy lifting when navigating between iPhone application screens. Chapter 4: Alerting Users The iPhone offers many ways to provide users with a heads up, from pop-up dialogs and progress bars to audio pings and status bar updates. Chapter 4 shows how to build these indications into your applications and expand your user-alert vocabulary. Chapter 5: Basic Tables Tables provide an interaction class that works particularly well on a small, cramped device. Many, if not most, apps that ship with the iPhone and iPod touch center on tables, including Settings,YouTube, Stocks, and Weather. Chapter 5 shows how iPhone tables work, what kinds of tables are available to you as a developer, and how you can use table features in your own programs. Chapter 6: Advanced Tables iPhone tables do not begin and end with simple scrolling lists.You can build tables with titled sections, with multiple scrolling columns, and more.You can add controls such as switches, create translucent cell backgrounds, and include custom fonts. Chapter 6 starts from where “Basic Tables” left off. It introduces advanced table recipes for you to use in your iPhone programs. Chapter 7: Media As you’d expect, the iPhone can load and display media from a wide variety of formats. It does music; it does movies. It handles images and Web pages.You can present PDF documents and photo albums and more. Chapter 7 shows way after way that you can import or download data into your program and display that data using the iPhone’s multitouch interface. Chapter 8: Control The UIControl class provides the basis for many iPhones interactive elements, including buttons, text fields, sliders, and switches. Chapter 8 introduces controls and their use, both through well-documented SDK calls and through lessdocumented ones. n n n n
Slide 20: Preface xix n n n Chapter 9: People, Places, and Things In addition to standard user interface controls and media components that you’d see on any computer, the iPhone SDK provides a number of tightly focused developer solutions specific to iPhone and iPod touch delivery. Chapter 9 introduces the most useful of these, including Address Book access (“people”), core location (“places”), and sensors (“things”). Chapter 10: Connecting to Services As an Internet-connected device, the iPhone is particularly suited to subscribing to Web-based services. Apple has lavished the platform with a solid grounding in all kinds of network computing services and their supporting technologies.The iPhone SDK handles sockets, password keychains, SQL access, XML processing, and more. Chapter 10 surveys common techniques for network computing and offering recipes that simplify day-to-day tasks. Chapter 11: One More Thing: Programming Cover Flow Although Cover Flow is not officially included in the iPhone SDK, it offers one of the nicest and most beautiful features of the iPhone experience.With Cover Flow, you can offer your users a gorgeously intense visual selection experience that puts standard scrolling lists to shame. Chapter 11 introduces Cover Flow and shows how you can use it in your applications. Prerequisites Here are basics you need on hand to begin programming for the iPhone or iPod touch: A copy of Apple’s iPhone SDK. Download your copy of the iPhone SDK from Apple’s iPhone Dev Center (http://developer.apple.com/iphone/).You must join Apple’s (free) developer program before you download. An iPhone or iPod touch. Although Apple supplies a simulator as part of its SDK, you really do need to have an actual unit to test on if you’re going to develop any serious software.You’ll be able to use the cable that shipped with your iPhone or iPod touch to tether your unit to the computer and install the software you’ve built. n n n n An Apple iPhone Developer License. You will not be able to test your software on an actual iPhone or iPod touch until you join Apple’s iPhone Developer program (http://developer.apple.com/iphone/program). Members receive a certificate that allows them to sign their applications and download them to the platforms in question for testing and debugging.The program costs $99/year for individuals and companies, $299/year for in-house enterprise development. An Intel-based Macintosh running Leopard. The SDK requires a Macintosh running Leopard OS X 10.5.3 or later. Apple requires an Intel-based computer in 32-bit mode. Many features do not work properly on PPC-based Macs or Intel Macs in 64-bit mode. Reserve plenty of disk space and at least 1GB of RAM.
Slide 21: xx Contents n n n At least one available USB 2.0 port. This enables you to tether your development iPhone or iPod touch to your computer for file transfer and testing. An Internet connection. This connection enables you to test your programs with a live WiFi connection as well as with EDGE. Familiarity with Objective-C. The SDK is built around Objective-C 2.0.The language is based on standard C with object-oriented extensions. If you have any object-oriented and C background, making the move to Objective-C is both quick and simple. Consult any Objective-C/Cocoa reference book to get up to speed. Note Although the SDK supports development for the iPhone and iPod touch, as well as possible yet-to-be-announced platforms, this book refers to the target platform as iPhone for the sake of simplicity. When developing for the touch, most material is applicable. This excludes certain obvious features such as telephony and onboard speakers. This book attempts to note such exceptions in the manuscript. Contacting the Author If you have any comments or questions about this book, please drop me an e-mail message at erica@ericasadun.com or stop by www.ericasadun.com. My Web site hosts many of the applications discussed in this book. Please feel free to visit, download software, read documentation, and leave your comments.
Slide 22: Acknowledgments This book would not exist without the efforts of Chuck Toporek, Romny French, Chris Zahn, and the entire AW production team (specifically Gary Adair, Keith Cline, Kristy Hart, Cheryl Lenser, Chelsey Marti, Jake McFarland, and Erika Millen). Thanks go as well to Neil Salkind, my agent of many years, to the tech reviewers who helped keep this book in the realm of sanity rather than wishful thinking, and to all my colleagues at TUAW and the Digital Media/Inside iPhone blog. I am deeply indebted to the wide community of iPhone developers, including Alex Schaefer, Nick Penree, James Cuff, Jay Freeman, Mark Montecalvo, August Joki, Max Weisel, Optimo, Kevin Brosius, Planetbeing, Pytey, Roxfan, UnterPerro,Youssef Francis, Bryan Henry, Daniel Peebles, ChronicProductions, Greg Hartstein, Emanuele Vulcano, np101137, and Sean Heber, among many others too numerous to name individually. Their techniques, suggestions, and feedback helped make this book possible. Special thanks go out to my family and friends, who supported me through month after month of new beta releases and who patiently put up with my unexplained absences and frequent howls of despair. I appreciate you all hanging in there with me. And thanks to my children for their steadfastness, even as they learned that a hunched back and the sound of clicking keys is a pale substitute for a proper mother.
Slide 23: About the Author Erica Sadun has written, coauthored, and contributed to about three dozen books about technology, particularly in the areas of programming, digital video, and digital photography. An unrepentant geek, Sadun has never met a gadget she didn’t need. Her checkered past includes run-ins with NeXT, Newton, iPhone, and myriad successful and unsuccessful technologies.When not writing, she and her geek husband parent three adorable geeks-in-training, who regard their parents with restrained bemusement.
Slide 24: 1 Introducing the iPhone SDK The iPhone and iPodfirst members of Apple’s newmobile platforms that arecomputing touch introduce innovative a joy to program.They are the family of pocket-based devices. Despite their diminutive proportions, they run a first-class version of OS X with a rich and varied SDK that enables you to design, implement, and realize a wide range of applications. For your projects, you can take advantage of the iPhone’s multitouch interface and fabulous onboard features using Xcode. In this chapter, you discover how the SDK is put together and learn to build your first iPhone-based Hello World applications. Apple’s iPhone SDK Are you ready to start programming for the iPhone? You’ll need Apple’s iPhone Software Developer Kit (SDK), which is free and available to members of Apple’s online (free) developer program. Download your copy of the iPhone SDK from Apple’s site at http://developer.apple.com/iphone. It consists of several components that form the basis of the iPhone development environment.These components include the following software: Xcode. Xcode is the most important tool in the iPhone development arsenal. It provides a comprehensive project development and management environment, complete with source editing, comprehensive documentation, and a graphical debugger. Xcode is built around several open source GNU tools, namely gcc (compiler) and gdb (debugger). Instruments. Instruments profiles how iPhone applications work under the hood. It samples memory usage and monitors performance.This lets you identify and target problem areas in your applications and work on their efficiency. Instruments offers graphical time-based performance plots that show where your applications are using the most resources. Instruments is build around the open source DTrace package developed by Sun Microsystems. Instruments plays a critical role in tracking down memory leaks and making sure your applications run efficiently on the iPhone platform. n n
Slide 25: 2 Chapter 1 Introducing the iPhone SDK n n n Dashcode. Dashcode creates stand-alone Web-based applications that run outside of a traditional browser environment. Conceptually, the iPhone version works just like the desktop version, complete with layout and debugging tools. Dashboard provides a Web-based development approach rather than native application compilation and is not covered in this book. Simulator. The iPhone Simulator runs on the Macintosh and enables you to create and test applications on your desktop.You can do this without connecting to an actual iPhone or iPod touch.The Simulator offers the same API used on the iPhone and provides a preview of how your concept designs will look.When working with the Simulator, Xcode compiles Intel x86 code that runs natively on the Macintosh rather than ARM-based code used on the iPhone. Interface Builder. Interface Builder (IB) provides a rapid prototyping tool that enables you to lay out user interfaces graphically and link to those prebuilt interfaces from your Xcode source code.With IB, you draw out your interface using visual design tools and then connect those onscreen elements to objects and method calls in your application. Together, the components of this iPhone SDK suite enable you to develop both traditional and Web-based applications. From a native application developer’s point of view, the most important components are Xcode and the Simulator, with Instruments providing an essential tuning tool. In addition to these tools, there’s an important piece not on this list.This piece ships with the SDK but is easy to overlook. I refer to Cocoa Touch. Cocoa Touch is the library of classes provided by Apple for rapid iPhone application development.This library, which takes the form of a number of framework libraries, enables you to build graphical event-driven applications using user interface elements such as windows, text, and tables. Cocoa Touch on the iPhone is analogous to AppKit on Mac OS X and supports creating rich, reusable interfaces on the iPhone. Many developers are surprised by the size of iPhone applications; they’re tiny. Cocoa Touch’s library support is the big reason for this. By letting Cocoa Touch handle all the heavy UI lifting, your applications can focus on getting their individual tasks done.The result is compact, focused code that does a single job at a time. Assembling iPhone Projects iPhone Xcode projects contain varied standard and custom components. Figure 1-1 shows a typical project. Project elements include source code, linked frameworks, and media such as image and audio files. Xcode compiles your source, links it to the frameworks, and builds an application bundle suitable for iPhone installation. It adds your media to this application bundle, enabling your program to access that media as the application runs on the iPhone. iPhone code is normally written in Objective-C 2.0.This is an object-oriented superset of ANSI C, which was developed from a mix of C and Smalltalk. If you’re unfamiliar with the language, Apple provides several excellent online tutorials at its
Slide 26: Assembling iPhone Projects 3 iPhone developer site. Among these are an introduction to object-oriented programming with Objective-C and an Objective-C 2.0 reference.These will quickly get you up to speed with the language. Frameworks are software libraries provided by Apple that supply the reusable class definitions for Cocoa Touch. Add frameworks to Xcode by dragging them onto your project’s Frameworks folder. After including the appropriate header files (such as UIKit/UIKit.h or QuartzCore/QuartzCore.h), you call their routines from your program. Associated media might include audio, image, and video files to be bundled with the package as well as text-based files that help define your application to the iPhone operating system. Drop media files into your project and reference them from your code. The project shown in Figure 1-1 is an especially simple one. It consists of a single source file (main.m) along with the default iPhone project frameworks (UIKit, Foundation, and Core Graphics) and a few supporting files (helloworld.png, Default.png, Icon.png, Info.plist).Together these items form all the materials needed to create a basic Hello World–style application. Note The HelloWorld_Prefix.pch file is created automatically by Xcode. It contains precompiled header files. NIB and XIB files (.nib, .xib) refer to files created in Interface Builder. These user interface definition files are linked to your application and called by your app at runtime. Figure 1-1 Xcode projects bring source code, frameworks, and media together to form the basis for iPhone applications.
Slide 27: 4 Chapter 1 Introducing the iPhone SDK iPhone Application Components Like their Macintosh cousins, iPhone applications live in application bundles. Application bundles are just folders named with an .app extension.Your program’s contents and resources reside in this folder, including the compiled executable, supporting media (such as images and audio), and a few special files that describe the application to the OS.The folder is treated by the operating system as a single bundle. Application Folder Hierarchy Unlike the Mac, iPhone bundles do not use Contents and Resources folders to store data or a MacOS folder for the executable. All materials appear at the top level of the folder. For example, instead of putting a language support .lproj folder into Contents/Resources/, Xcode places it directly into the top .app folder.You can still use subfolders to organize your project, but these are ad hoc user-defined folders and do not follow any standard. The iPhone SDK’s core OS support includes the NSBundle class.This class makes it easy to locate your application’s root folder and to navigate down to your custom subfolders to point to and load resources. Note As on a Macintosh, user domains mirror system ones. Official Apple-distributed applications reside in the primary /Applications folder. Third-party applications live in /var/mobile/ Applications instead. For the most part, the underlying UNIX file system is obscured by the iPhone’s sandbox, which is discussed later in this section. The Executable The executable file of your application resides at the top-level folder of the application bundle. It must carry executable permissions to run properly and must be authenticated by SpringBoard, the iPhone’s version of Finder. Starting with firmware 1.2, which was released only to developers, SpringBoard instituted a watchdog feature to prevent arbitrary code execution.This feature put a damper on the use of command-line utilities that you find on other UNIX platforms. SpringBoard’s watchdog feature also added memory utilization limits.The system shuts down any process that uses too many system resources. The Info.plist File As on a Macintosh, the iPhone application folder contains that all-important Info.plist file. Info.plist files are XML property lists that describe the application to the operating system. Property lists store key-value pairs for many different purposes and can be saved in readable text-based or compressed binary formats. In an Info.plist file, you specify the application’s executable (CFBundleExecutable) and identifier (CFBundleIdentifier). This identifier is critical to proper behavior and execution.
Slide 28: iPhone Application Components 5 Use the standard Apple domain naming formats (for example, com.sadun.appname) in your applications by editing your project’s settings in Xcode (see Figure 1-2). Specify your personal domain and let Xcode append the product identifier.To change identifiers, right-click your project file in Xcode and choose Get Info from the pop-up. Use the Search field to find Product_Name and then edit that value as needed. Figure 1-2 Customize your application’s bundle identifier by editing the Info.plist file. The PRODUCT_NAME identifier is specified in your project’s settings. The product identifier enables you to communicate with other applications and to properly register your application with SpringBoard, the “Finder” of the iPhone. SpringBoard runs the home screen from which you launch your applications.The product identifier also forms the basis for the built-in preferences system, the user defaults. Applications preferences are automatically stored in the user Library (in /var/mobile/ Library/Preferences) using the application’s identifier.This identifier is appended with the .plist extension (for example, com.sadun.appname.plist), and the preferences are stored using a binary plist format.You can read a binary plist by transferring it to a Macintosh. Use Apple’s plutil utility to convert from binary to a text-based XML format: plutil –convert xml1 plistfile. Apple uses binary plists to lower storage requirements and increase system performance. As with the Macintosh, Info.plist files offer further flexibility and are highly customizable.With them, you can set SpringBoard variables (for example, SBUsesNetwork) or specify how your icon should display (for example, UIPrerenderedIcon). Some SpringBoard variables enable you to define multiple roles for a single application. For example, the Photos and Camera utilities are actually the same application, MobileSlideShow, playing separate “roles.”You can also specify whether the application is hidden from view.
Slide 29: 6 Chapter 1 Introducing the iPhone SDK Other standard Info.plist keys include UIStatusBarStyle for setting the look and color of the status bar and UIStatusBarHidden for hiding it altogether. UIInterfaceOrientation lets you override the accelerometer to create a landscapeonly (UIInterfaceOrientationLandscapeRight) presentation. Register your custom application URL schemes (for example, myCustomApp://) by setting CFBundleURLTypes. See Chapter 10, “Connecting to Services,” for more information about URL schemes. The Icon and Default Images Icon.png and Default.png are two key image files. Icon.png acts as your application’s icon, the image used to represent the application on the SpringBoard home screen. Default.png (officially known as your “launch image”) provides the splash screen displayed during application launch. Unlike Default.png, the icon filename is arbitrary. If you’d rather not use “icon.png,” set the CFBundleIconFile key in your Info.plist file to whatever filename you want to use. Apple recommends matching Default.png to your application’s background. Many developers use Default.png launch images for a logo splash or for a “Please wait” message. These go against Apple’s human interface guidelines (launch images should provide visual continuity, not advertising or excuses for delays) but are perfectly understandable uses. The “official” application icon size is 57-by-57 pixels. SpringBoard automatically scales larger art. Provide flat (not glossy) art with squared corners. SpringBoard smoothes and rounds those corners and adds an automatic gloss and shine effect. If for some compelling reason you need to use prerendered art, set UIPrerenderedIcon to <true/> in your Info.plist file. Note If you plan to submit your application to App Store, you need to create a high-resolution (512-by-512 pixel) version of your icon. Although you can up sample your 57-by-57 icon.png art, it won’t look good. Going the other way allows you to maintain high-quality art that you can compress to your icon as needed. XIB (NIB) files Interface Builder creates XIB (also called NIB on the Macintosh) files that store precooked addressable user interface classes.These files appear at the top level of your application bundle and are called directly from your program. At the time of this writing, the Interface Builder filename has not yet stabilized, although the .xib (Xcode Interface Builder) extension seems to be winning out for iPhone. Note When you develop programs that do not use XIB or NIB Interface-Builder bundles, remove the NSMainNibFile key from Info.plist and discard the automatically generated MainWindow.xib file from to your project.
Slide 30: iPhone Application Components 7 Files Not Found in the Application Bundle As with the Macintosh, things you do not find inside the application bundle include preferences files (generally stored in the application sandbox in Library/Preferences), application plug-ins (stored in /System/Library at this time and not available for general development), and documents (stored in the sandbox in Documents). Another thing that seems to be missing (at least from the Macintosh programmer point of view) is Application Support folders. Copy support data, which more rightfully would be placed into an Application Support structure, to your Documents or Library folders. Sandboxes The iPhone OS restricts all SDK development to application “sandboxes” for the sake of security.The iPhone sandbox limits your application’s access to the file system to a minimal set of folders, network resources, and hardware. It’s like attending an overly restrictive school with a paranoid principal: Your application can play in its own sandbox, but it can’t visit anyone else’s sandbox. You cannot share toys.You cannot share data.You cannot mess in the administrative offices.Your files must stay in the folders provided to you by the sandbox, and you cannot copy files to or from other application folders. Your application owns its own Library, Documents, and /tmp folders.These mimic the standard folders you’d use on a less-restrictive platform but specifically limits your ability to write and access this data. n n n In addition to these limitations, your application must be signed digitally and authenticate itself to the operating system with a coded application identifier, which you must create at Apple’s developer program site. On the bright side, sandboxing ensures that all program data gets synced whenever your device is plugged into its home computer. On the downside, at this time Apple has not clarified how that synced data can be accessed from a Windows- or Macintosh-based desktop application. (Chapter 7, “Media,” discusses recovering data from the mdbackup files created by iTunes and its Mobile Devices framework.) Note Sandbox specification files (using the .sb extension) are stored in /var/mobile/Applications along with the actual sandbox folders. These files control privileges such as read-and-write access to various bits of the file system. If such a possibility should present itself, do not edit this file directly. You will render your application unusable. An exemplar sandbox file usually appears in /usr/share/sandbox.
Slide 31: 8 Chapter 1 Introducing the iPhone SDK Platform Limitations When talking about mobile platforms like the iPhone, several concerns always arise, such as storage, interaction limits, and battery life. Mobile platforms can’t offer the same disk space their desktop counterparts do. And along with storage limits, constrained interfaces and energy consumption place very real restrictions on what you as a developer can accomplish. With the iPhone, you can’t design for a big screen, for a mouse, for a physical keyboard, or even for a physical always-on A/C power supply. Instead, platform realities must shape and guide your development. Fortunately, Apple has done an incredible job designing a new platform that somehow leverages flexibility from its set of limited storage, limited interaction controls, and limited battery life. Storage Limits The iPhone hosts a powerful yet compact OS X installation. Although the entire iPhone OS fills no more than a few hundred megabytes of space—almost nothing in today’s culture of large operating system installations—it provides an extensive framework library. These frameworks of precompiled routines enable iPhone users to run a diverse range of compact applications, from telephony to audio playback, from e-mail to Web browsing. The iPhone provides just enough programming support to create flexible interfaces while keeping system files trimmed down to fit neatly within tight storage limits. Data Access Limits Every iPhone application is sandboxed.That is, it lives in strictly regulated portion of the file system.Your program cannot access from other applications and from certain cordoned-off folders including the onboard iTunes library. It can, however, access any data that is freely available over the Internet when the iPhone is connected to a network. Memory Limits On the iPhone, memory management is critical.The iPhone does not support disk-swapbased virtual memory.When your run out of memory, the iPhone reboots—as Apple puts it, random reboots are probably not the user experience you were hoping for.With no swap file, you must carefully manage your memory demands and be prepared for the iPhone OS to terminate your application if it starts swallowing too much memory at once.You must also take care as to what resources your applications use.Too many highresolution images or audio files can bring your application into the autoterminate zone. Note Xcode automatically optimizes your PNG images using the pngcrush utility shipped with the SDK. (You’ll find the program in the iPhoneOS platform folders in /Developer. Run it from the command line with the –iphone switch to convert standard PNG files to iPhoneformatted ones.) For this reason, use PNG images in your iPhone apps where possible as your preferred image format.
Slide 32: Platform Limitations 9 Interaction Limits Losing physical input devices and working with a tiny screen doesn’t mean you lose interaction flexibility.With multitouch, you can build user interfaces that defy the rules. The iPhone’s touch technology means you can design applications complete with text input and pointer control using a virtual screen that’s much larger than the actual physical reality held in your palm. A smart autocorrecting onscreen keyboard and an accelerometer that detects orientation provide just two of the key technologies that separate the iPhone from the rest of the mobile computing pack.What this means, however, is that you need to cut back on things such as text input and scrolling windows. Focus your design efforts on easy-to-tap interfaces rather than on desktop-like mimicry. Remember, you can use just one window at a time—unlike desktop applications that are free to use multiwindow displays. Note The iPhone screen supports up to five touches at a time, although it’s rare to find any application that uses more than two at once. Energy Limits For mobile platforms, you cannot ignore energy limitations.That being said, Apple’s SDK features help to design your applications to limit CPU use and avoid running down the battery. A smart use of technology (for example, like properly suspending programs) lets your applications play nicely on the iPhone and keeps your software from burning holes in users’ pockets (sometimes almost literally). Some programs when left running produce such high levels of waste heat that the phone becomes hot to the touch and the battery quickly runs down.The Camera application is one notable example. Application Limits Apple has instituted a strong “one-application-at-a-time” policy.That means as a thirdparty developer you cannot develop applications that run in the background like Apple’s Mail and Phone utilities. Each time your program runs, it must clean up and metaphorically get out of Dodge before passing control on to the next application selected by the user.You can’t leave a daemon running that checks for new messages or that sends out periodic updates. An “Open SDK” created by hobbyists exists that bypasses this limitation, but applications built with those tools cannot be added to and sold through the iPhone App Store. On the other hand,Apple does support push data from Web services. Registered services can push badge numbers and messages to users, letting them know that data is waiting on those servers.
Slide 33: 10 Chapter 1 Introducing the iPhone SDK Note According to the iPhone Terms of Service, you may not create external frameworks for your iPhone application or use Cocoa’s plug-in architecture for applications submitted to the App Store. User Behavior Limits Although it’s not a physical device-based limitation, get used to the fact that iPhone users approach phone-based applications sporadically.They enter a program, use it quickly, and then leave just as quickly.The handheld nature of the device means you must design your applications around short interaction periods and prepare for your application to be cut off as a user sticks the phone back into a pocket. Save your application state between sessions and relaunch quickly to approximate the same task your user was performing the last time the program was run. SDK Limitations As you might expect, building applications for the iPhone is similar to building applications for the Macintosh.You use Objective-C 2.0.You compile by linking to an assortment of frameworks. In other ways, the iPhone SDK is limited. Here are some key points to keep in mind: Garbage Collection is MIA and probably always will be. Apple insiders suggest that platform limitations simply do not allow for garbage collection to be implemented in any sane and useful manner.You are responsible for retaining and releasing objects in memory. Many libraries are only partly implemented. Core Animation is partially available through the Quartz Core framework, but many classes and methods remain missing in action.The lesson here is that you’re working in early-release software.Work around the missing pieces and make sure to submit your bug reports to Apple so that it (we hope) fixes the parts that need to be used. Be aware that Apple has deliberately cut access to some proprietary classes. The public SDK frameworks are not as varied as the private ones. In the original iPhone open SDK jailbreak world, you used to be able to call on the iTunes Store frameworks to search the mobile store and the Celestial framework for easy QuickTime-like audio/video playback.With the debut of the official SDK, these are no longer publicly available, and Apple has limited third-party development strictly to a public framework subset. n n n
Slide 34: Model-View-Controller 11 Programming Paradigms iPhone programming centers on two important paradigms: objected-oriented programming and the Model-View-Controller (MVC) design pattern.The iPhone SDK is designed around supporting these concepts in the programs you build.To do this, it has introduced delegation (controller) and data source methods (model) and customized view classes (view). Here is a quick rundown of some important iPhone/Cocoa Touch design vocabulary used through this book. Object-Oriented Programming Objective-C is heavily based on Smalltalk, one of the most historically important objectoriented languages. Object-oriented programming uses the concepts of encapsulation and inheritance to build reusable classes with published external interfaces and private internal implementation.You build your applications out of concrete classes that can be stacked together like Lego toys, because it’s always made clear which pieces fit together through class declarations. Multiple inheritance is an important feature of Objective-C’s approach to objectoriented programming. iPhone classes can inherit behaviors and data types from more than one parent.Take the class UITextView, for example. It’s both text and a view. Like other view classes, it can appear onscreen. It has set boundaries and a given opacity. At the same time, it inherits text-specific behavior.You can easily change its display font, color, or text size. Objective-C and Cocoa Touch combine these behaviors into a single easy-to-use class. Model-View-Controller MVC separates the way an onscreen object looks from the way it behaves. An onscreen button (the view) has no intrinsic meaning. It’s just a button that users can push.That view’s controller acts as an intermediary. It connects user interactions such as button taps to targeted methods in your application, which is the model.The application supplies and stores meaningful data and responds to interactions such as these button taps by producing some sort of useful result. Each MVC element works separately.You might swap out a push button with, for example, a toggle switch without changing your model or controller.The program continues to work as before, but the GUI now has a different look. Alternatively, you might leave the interface as is and change your application where a button triggers a different kind of response in your model. Separating these elements enables you to build maintainable program components that can be updated independently. The MVC paradigm on the iPhone breaks down into the following categories: n View. View components are provided by children of the UIView class and by its associated (and somewhat misnamed) UIViewController class.
Slide 35: 12 Chapter 1 Introducing the iPhone SDK n n Controller. The controller behavior is implemented through three key technologies: delegation, target-action, and notification. Model. Model methods supply data through protocols such as data sourcing and meaning by implementing callback methods triggered by the controller. Together these three elements form the backbone of the MVC programming paradigm. Let’s look at each of these elements of the iPhone MVC design pattern in a bit more detail.The following sections introduce each element and its supporting classes. View Classes The iPhone builds its views based on two important classes: UIView and UIViewController.These two classes are responsible for defining and placing all onscreen elements. As views draw things on your screen, UIView represents the most abstract view class. Nearly all user interface classes descend from UIView and its parent UIResponder.Views provide all the visual application elements that make up your application. Important UIView classes include UITextViews, UIImageViews, UIAlertViews, and so forth.The UIWindow class, a kind of UIView, provides a viewport into your application and provides the root for your display. Because of their onscreen nature, all views establish a frame of some sort.This is an onscreen rectangle that defines the space each view occupies.The rectangle is established by the view’s origin and extent. Views are hierarchical and are built with trees of subviews.You can display a view by setting it as your main window’s content view, or you can add it to another view by using the addSubview method to assign a child to a parent.You can think about views as attaching bits of transparent film to a screen, each of which has some kind of drawing on it.Views added last are the ones you see right away.Views added earlier may be obscured by other views sitting on top of them. Despite the name, the UIViewController class does not act strictly as controllers in the MVC sense.They’re responsible for laying items out on the screen and obscuring many of the more intricate layout details. Apple terminology does not always match the MVC paradigm taught in computer science classes. First and foremost, view controllers are there to make your life easier.They take responsibility for rotating the display when a user reorients his or her iPhone.They resize views to fit within the boundaries when using a navigation bar or a toolbar.They handle all the interface’s fussy bits and hide the complexity involved in directly managing interaction elements.You can design and build iPhone applications without ever using a UIViewController or one of its subclasses, but why bother? The class offers so much convenience it’s hardly worth writing an application without them. In addition to the base controller’s orientation and view resizing support, two special controllers, the UINavigationController and UITabBarController, magically handle view shifting for you.The navigation version enables you to drill down between views, smoothly sliding your display between one view and the next. Navigation controllers
Slide 36: Model-View-Controller 13 remember which views came first and provide a full breadcrumb trail of “back” buttons to return to previous views without any additional programming. The tabbed view controller lets you easily switch between view controller instances using a tabbed display. So if your application has a top ten list, a game play window, and a help sheet, you can add a three-buttoned tab bar that instantly switches between these views without any additional programming to speak of. Every UIViewController subclass implements its own loadView method.This is the method that lays out the controller’s subviews and sets up all the triggers, callbacks, and delegates. So in that sense alone, the UIViewController does act as a controller by providing these links between the way things look and how interactions are interpreted. And, because you almost always send the callbacks to the UIViewController itself, it often acts as your model in addition to its primary role as a controller for whatever views you create and want to display. It’s not especially MVC, but it is convenient and easy to program. Controller When Apple designs interactive elements such as sliders and tables, they have no idea how you’ll use them.The classes are deliberately general.With MVC, there’s no programmatic meaning associated with row selection or button presses. It’s up to you as a developer to provide the model that adds meaning.The iPhone provides several ways in which prebuilt Cocoa Touch classes can talk to your custom ones. Here are the three most important: delegation, target-action, and notifications. Delegation Many UIKit classes use delegation to hand off responsibility for responding to user interactions.When you set an object’s delegate, you tell it to pass along any interaction messages and let that delegate take responsibility for them. UITableViews are a good example of this.When a user taps on a table row, the UITableView has no built-in way of responding to that tap. Instead, it consults its delegate—usually a view controller class or your main application delegate—and passes along the selection change through a delegate method. The UITableView delegate method tableView: didSelectRowAtIndexPath: is a typical example.Your model takes control of this method and implements how it should react to the row change.You might display a menu or navigate to a subview or place a check mark next to the current selection.The response depends entirely on how you implement the delegated selection change method. To set an object’s delegate, use some variation on the setDelegate: method.This instructs your application to redirect interaction callbacks to the delegate.You let Xcode know that your object implements delegate calls by adding a mention of the delegate protocol it implements in the class declaration.This appears in angle brackets, to the right of the class inheritance. Listing 1-1 shows a kind of UIViewController that implements delegate methods for UITableView views.The MergedTableController class is, therefore, responsible for implementing all required table delegate methods.
Slide 37: 14 Chapter 1 Introducing the iPhone SDK Delegation isn’t limited to Apple’s classes. It’s simple to add your own protocol declarations to your classes and use them to define callback vocabularies. Listing 1-1 creates the FTPHostDelegate protocol, which declares the ftpHost instance variable.When used, that object must implement all three methods declared in the protocol. Note If your application is built around a central table view, use UITableViewController instances to simplify table creation and use. Listing 1-1 Defining and Adding Delegate Protocols Declarations to a Class Definition @protocol FTPHostDelegate <NSObject> - (void) percentDone: (NSString *) percent; - (void) downloadDone: (id) sender; - (void) uploadDone: (id) sender; @end @interface MergedTableController : UIViewController <UITableViewDelegate, UITableViewDataSource> { UIView *contentView; UITableView *subView; UIButton *button; id <FTPHostDelegate> *ftpHost; SEL finishedAction; } @end Target-Action Target-actions are a lower-level way of redirecting user interactions.You’ll encounter these almost exclusively for children of the UIControl class.With target-action, you tell the control to contact a given object when a specific user event takes place. For example, you’d specify which object to contact when users press a button. Listing 1-2 shows a typical example.This snippet defines a UIBarButtonItem instance, a typical button-like control used in iPhone toolbars. It sets the item’s target to self and the action to @selector(setHelvetica:).When tapped, it triggers a call to the defining object sending the setHelvetica: message. Listing 1-2 Using Target-Actions for Adding Responses to Controls UIBarButtonItem *helvItem = [[[UIBarButtonItem alloc] initWithTitle:@"Helvetica" style:UIBarButtonItemStyleBordered target:self action:@selector(setHelvetica:)] autorelease];
Slide 38: Model-View-Controller 15 As you can see, the name of the method (setHelvetica:) is completely arbitrary. Target-actions do not rely on an established method vocabulary the way delegates do. In use, however, they work exactly the same way.The user does something, in this case presses a button, and the target implements the selector to provide a meaningful response. Whichever object defines this UIBarButtonItem instance must implement a setHelvetica: method. If it does not, the program will crash at runtime with an undefined method call error. Standard target-action pairs always pass a single argument, the interaction object. In this case, this is the UIBarButtonItem instance that was pressed.This self-reference, where the triggered object is included with the call, enables you to build more general action code. Instead of building separate methods for setHelvetica:, setGeneva:, and setCourier:, you could create a single setFontFace: method to update a font based on which button the user pressed. To build target-action into your own classes, add a target variable of type id (any object class) and an action variable of type SEL (method selector). Notifications In addition to delegates and target-actions, the iPhone uses yet another way to communicate about user interactions between your model and your view—and about other events, for that matter. Notifications enable objects in your application to talk among themselves, as well as to talk to other applications on your system. By broadcasting information, notifications enable objects to send state messages: “I’ve changed,” “I’ve started doing something,”or “I’ve finished.” Other objects might be listening to these broadcasts, or they might not. For your objects to “hear” a notification, they must register with a notification center and start listening for messages.The iPhone implements at least four kinds of notification centers: n NSNotificationCenter. This is the gold standard for in-application notification. You can subscribe to any or all notifications with this kind of notification center and listen as your objects talk to each other.The notifications are fully implemented and can carry data as well as the notification name.This name + data implementa tion offers great flexibility, and you can use this center to perform complex messaging. n NSDistributedNotificationCenter. This center is meant for interapplication notification. It is not fully implemented on the iPhone and should be avoided. n DarwinNotificationCenter. The iPhone relies on Darwin notification centers for interapplication messaging. It’s limited in that it enables you to only broadcast announcements and will not let you send data with those announcements. So you can announce that something has changed, but you can’t send along information about which item has changed. Despite this limitation, Darwin notification is reliable and robust. Messages arrive dependably. Darwin notification is built using standard BSD notification (for example, notify_post(), notify_register_ mach_port(), and so on).
Slide 39: 16 Chapter 1 Introducing the iPhone SDK n TelephonyNotificationCenter. Telephony notifications are private and unpublished. Unfortunately, Apple did not open up this center, but if you sneak your way into listening to this special-purpose center, you’ll know when phone calls and SMS messages arrive. It’s easy to subscribe to a notification center. Add your application delegate or, more typically, your UIViewController as a registered observer.You supply an arbitrary selector to be called when a notification arrives, in this case trackNotifications:.The method takes one argument, an NSNotification. Ensure that your callback method will hear all application notifications by setting the name and object arguments to nil. All notifications contain three data elements: the notification name, an associated object, and a user information dictionary. If you’re unsure what notifications UIKit objects in your application produce, have your callback print out the name from all the notifications it receives—for example, NSLog(@"%@", [notification name]). Apple does not document notification protocols with the same love and care that it documents delegate and data source protocols. The kinds of notification vary by the task you are performing. For example, notifications when rotating an application include UIApplicationWillChangeStatusBarOrientation Notification and UIDeviceOrientationDidChangeNotification. In some cases, these correspond strongly with existing delegate methods. In other cases, they don’t, so you’d be wise to monitor notifications while writing programs to find any gaps in Apple’s delegate protocol implementations. Here’s how you listen: [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(trackNotifications:) name:nil object:nil]; Note The recipes in this book generally use printf rather than NSLog() as the former worked more reliably during the SDK beta period. Model You’re responsible for building all application semantics—the model portion of any MVC app.You create the callback methods triggered by your application’s controller and provide the required implementation of any delegate protocol.There’s one place, however, that the iPhone SDK gives you a hand with meaning, and that’s with data sources. Data sources enable you to fill UIKit objects with custom content. Data Sources A data source refers to any object that supplies another object with on demand data. Some UI objects are containers without any native content.When you set another object as its data source, usually via a call like [uiobject setDataSource:applicationobject], you enable the UI object (the view) to query the data source (the model) for data such as table cells for a given UITableView. Usually the data source pulls its data in from a file
Slide 40: Model-View-Controller 17 such as a local database, from a Web service such as an XML feed, or from a scanned source such as locally detected WiFi hotspots.UITableView and UIPickerView are two of the few Cocoa Touch classes that support or require data sources. Data sources are like delegates in that you must implement their methods in another object, typically the UITableViewController that owns the table.They differ in that they create/supply objects rather than react to user interactions. Listing 1-3 shows a typical data source methods method that returns a table cell for a given row. Like other data source methods, it enables you to separate implementation semantics that fill a given view from the Apple-supplied functionality that builds the view container. Objects that implement data source protocols must declare themselves just as they would with delegate protocols. Listing 1-1 showed a class declaration that supports both delegate and data source protocols for UITableViews. Apple thoroughly documents data source protocols. Listing 1-3 Content Data Source Methods Supply Information That Fills a View with Meaningful // Return a cell for the ith row, labeled with its number - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier: @"any-cell"]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:@"any-cell"] autorelease]; } // Set up the cell cell.text = [tableTitles objectAtIndex:[indexPath row]]; cell.editingStyle = UITableViewCellEditingStyleDelete; return cell; } The UIApplication Object In theory, you’d imagine that the iPhone “model” component would center on the UIApplication class. In practice, it does not, at least not in any MVC sense of the word model. In the world of the Apple SDK, each program contains precisely one UIApplication instance, which you can refer to via [UIApplication sharedInstance]. For the most part, unless you need to open a URL in Safari, recover the key window, or adjust the look of the status bar, you can completely ignore UIApplication. Build your program around a custom application delegate class that is responsible for setting things up when the application launches and closing things down when the application terminates. Otherwise, hand off the remaining model duties to methods in your custom UIViewController classes or to custom model classes.
Slide 41: 18 Chapter 1 Introducing the iPhone SDK Note Use [[UIApplication sharedInstance] keyWindow] to locate your application’s main window object. Uncovering Data Source and Delegate Methods In addition to monitoring notifications, message tracking can prove to be an invaluable tool. Add the following snippet to your class definitions to expose all the methods—both documented and undocumented, data source and delegate—that your class responds to: -(BOOL) respondsToSelector:(SEL)aSelector { printf("SELECTOR: %s\n", [NSStringFromSelector(aSelector) UTF8String]); return [super respondsToSelector:aSelector]; } Building an iPhone Application Skeleton Nearly every iPhone application you build will contain a few key components. Here is a quick rundown of those components, how often you’ll use them, and what they do: The main() function (always use). Every C-based program centers around a main() function. For the iPhone, this function primes memory management and starts the application event loop. The applicationDidFinishLaunching: method (always use). This method is the first thing triggered in your program.This is where you create a basic window, set its contents, and tell it to become the key responder for your application. The applicationWillTerminate: method (usually use). This method enables you to handle any status finalization before handing control back to SpringBoard. Use this to save defaults, update data, and close files. The loadView method (always use). Assuming you’ve built your application around a UIViewController—and there’s usually no reason not to do so—the mandatory loadView method sets up the screen and lays out any subviews. Make sure to call [super loadView] whenever you inherit from a specialized subclass such as UITableViewController or UITabBarController. The shouldAutorotateToInterfaceOrientation: method (usually use). Unless you have pressing reasons to force your user to remain in portrait orientation, add the should-autorotate method to allow the UIViewController method to automatically match your screen to the iPhone’s orientation. n n n n n There are many other methods you’ll use over and over again.These five provide important touch points that you should consider every time you create a new application.
Slide 42: The Hello World Application 19 The Hello World Application Listing 1-4 provides a basic image-based Hello World application.This application is built using a UINavigationController and a custom UIViewController (called HelloController here) that displays a picture. As the name suggests, the application does little more than open itself and present itself onscreen.What you get here, therefore, are all the essentials.These are the skeletal features on which you can hang the body of your application when you’re ready to start writing more meaningful code. The Classes A navigation controller is responsible for creating that blue-gray header with the title you see in Figure 1-3. Although the header does little in this simple demonstration, in real-world apps it’s a critical player.You’ll see navigation bars in action when looking at the iPhone Mail and Safari applications.The UINavigationController class simplifies adding these features to your application. Figure 1-3 UIViewController controllers can automatically handle view orientation changes by scaling their subviews. When working with images, you’ll probably want to catch orientation changes and swap out a landscape-friendly version rather than accept the squeezed aspect shown here. Here, the view controller loads an image and handles reshaping it for orientation changes. Figure 1-3 shows the interface built by this source in both portrait and landscape
Slide 43: 20 Chapter 1 Introducing the iPhone SDK orientation. Clearly, when dealing with images, you’ll probably want to catch orientation changes and swap out landscape image versions for portrait ones and vice versa. I chose not to in this sample for two reasons. First, so you would get a clear visual of how the automatic reshaping takes place. Second, to understand how powerful this reshaping is— with almost no code, the application handles reorientation all by itself. The Code This program contains definitions for two classes (HelloController and SampleAppDelegate) plus the main() function.This code, like all code in this book, appears together as a single file. Rather than provide the five separate files this code would normally entail, a combined listing makes this far more readable in book form. I strongly encourage you to use the standard multifile system for your real applications. The main() function was generated automatically by Xcode and remains essentially untouched by human hands. It calls UIApplicationMain(), passing it the name of the main application delegate, which in this case is called SampleAppDelegate—for no other reason than I call all the sample-code application delegates in this book that. Feel free to name your own delegates as desired. The applicationDidFinishLaunching[colon] method is called next. Here, the code creates a new window using the standard mainScreen geometry. It builds a navigation controller and assigns a new HelloController—my UIViewController subclass—as its root view controller.That assigns the HelloController view as the navigation controller’s primary subview. Doing just this enables this program to support the full range of navigation bar features. To finish setting up the window, this program sets nav.view (the entire view headed by that navigation bar) as the window’s subview and orders the window out. In the HelloController class, loadView creates the main application view, which in this case is nothing more than a UIImageView loaded with the contents of helloworld.png. Using self.view = contentView assigns the image view to the controller. Setting a few flags for autorotation and adding shouldAutorotateToInterfaceOrientation: ensures the application responds to iPhone orientation changes. A Note About Sample Code and Memory Management The Hello World code that follows is the first of many samples throughout this iPhone Developer’s Cookbook. This book was written during the public SDK beta period starting in March 2008. During that time, Apple released several iterations of the SDK, which constantly underwent changes in terms of class definitions and, more important, memory management. All the sample code has been written and rewritten, tested and retested to make sure that it continues to work with each SDK revision. I have loosened memory management in the code throughout this book to ensure that the samples remain robust and working. If you wonder, while reading through code, about
Slide 44: The Hello World Application 21 seemingly extraneous retains and a lack of matching releases, it is all to that end, to ensure that the sample code continues to operate. Feel free to tighten things where desired. All samples in this book use the same base project (for example, Hello World).This ensures that the samples will not overwhelm your device with a hundred odd stray icons and names.You can find up-to-date sample code, Xcode projects, and video at my site, ericasadun.com. Listing 1-4 Hello World #import <UIKit/UIKit.h> @class UIImageView; // Custom UIViewController displays a simple image @interface HelloController : UIViewController { UIImageView *contentView; } @end @implementation HelloController - (id)init { if (self = [super init]) { self.title = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleName"]; // place any further initialization here } return self; } - (void)loadView { // Load an application image and set it as the primary view contentView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] ➥applicationFrame]]; [contentView setImage:[UIImage imageNamed:@"helloworld.png"]]; self.view = contentView; [contentView release]; // reduce retain count by one // Provide support for auto-rotation and resizing contentView.autoresizesSubviews = YES; contentView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | ➥UIViewAutoresizingFlexibleHeight); } // Allow the view to respond to iPhone Orientation changes
Slide 45: 22 Chapter 1 Introducing the iPhone SDK Listing 1-4 Continued -(BOOL)shouldAutorotateToInterfaceOrientation: (UIInterfaceOrientation)interfaceOrientation { return YES; } -(void) dealloc { // add any further clean-up here [contentView release]; [super dealloc]; } @end // Application Delegate handles application start-up and shut-down @interface SampleAppDelegate : NSObject <UIApplicationDelegate> { } @end @implementation SampleAppDelegate // On launch, create a basic window - (void)applicationDidFinishLaunching:(UIApplication *)application { UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] ➥bounds]]; UINavigationController *nav = [[UINavigationController alloc] ➥initWithRootViewController:[[HelloController alloc] init]]; [window addSubview:nav.view]; [window makeKeyAndVisible]; } - (void)applicationWillTerminate:(UIApplication *)application // handle any final state matters here } - (void)dealloc { [super dealloc]; } @end int main(int argc, char *argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; int retVal = UIApplicationMain(argc, argv, nil, @"SampleAppDelegate"); [pool release]; return retVal; } {
Slide 46: Building Hello World 23 Building Hello World The following sections create the Hello World iPhone application using Xcode and the iPhone SDK.You’ll create a new iPhone project, customize it a bit, and swap in the Hello World sample code from Listing 1-4. Figure 1-4 The New Project window contains three iPhone application templates that you can use to build your programs. Create an iPhone Project To create Hello World, you need a fresh, new project in Xcode. Select File, New Project (Command-Shift-N).The New Project window (see Figure 1-4) opens. Select iPhone, Application, Cocoa Touch Application (View Based Application in newer versions of Xcode), and click Choose. Use the standard Leopard controls to navigate to where you want to save your new application, enter a name (Hello World), and click Save. Xcode opens a new iPhone project window and populates it with all the basic elements and frameworks you need to build your first iPhone application. Items you will see in this project include the following: n Foundation and Core Graphics frameworks. These essential frameworks enable you to build your iPhone applications using the same fundamental classes and calls you are familiar with from the Macintosh.
Slide 47: 24 Chapter 1 Introducing the iPhone SDK n n n n n UIKit framework. This framework provides iPhone-specific user interface elements and is key to developing applications that can be seen and interacted with on the iPhone screen. HelloWorld.app. Displayed in red, this placeholder will be used to store your finished application. Like on the Macintosh, iPhone applications are bundles and consist of many items stored in a central folder. Info.plist. This file describes your application to the iPhone’s system and enables you to specify its executable, its application identifier, and other key features. It works in the same way Info.plist files work on the Mac. mainWindow.xib. This Interface Builder file creates an unpopulated window. You will not use this for this first walk-through. main.m, HelloWorldAppDelegate.h, HelloWorldAppDelegate.m, and so on. These files contain a rough skeleton that you can customize and expand to create your application. Running the Skeleton If you like, choose Run, Run.The program displays an all-black screen, and you can exit by tapping the simulated Home key.The standard project skeleton does little more than launch an empty window. By default, projects always compile for and launch in the simulator. You tell Xcode whether to build your application for the Leopard-based simulator or for the iPhone by choosing Project, Set Active SDK.You cannot at the time of writing load your software onto an iPhone without a developer certificate.The iPhone Developer Program starts at $99/year and offers access to the on-iPhone App Store.To apply for the program, visit http://developer.apple.com/iphone/program. Customize the iPhone Project The following steps convert the standard skeleton into your Hello World project: 1. Remove classes. Select the Classes folder in the Groups & Files column on the left and press Delete. Xcode asks you to confirm. Click Also Move to Trash. 2. Remove the .xib file. You won’t want to use it for this project. 3. Remove two lines from the Info.plist file. These are the lines with the NSMainNibFile key and the line that immediately follows after, the MainWindow string. 4. Add an Images folder. Right-click Hello World in the Groups & Files column and choose Add, New Group. Name the new folder Pictures. 5. Add images to the project. Drag the three images from the Chapter One project folder provided with this book onto the Pictures folder: Icon.png, Default.png, and helloworld.png. Check Copy Items into Destination Group’s Folder (if needed) and click Add.
Slide 48: Building Hello World 25 6. Replace main.m. Open main.m and replace all the text in that file with the text from the main.m file provided in the Chapter One project folder. Save your changes with File, Save (Command-S) and close the main.m window. 7. Select the iPhone Simulator. Choose Project, Set Active SDK, iPhone Simulator. 8. Run it. Choose Build, Build & Run (Command-R).The program will compile and launch in the iPhone simulation window. Here are a few how-tos you’ll want to know about while running a simulated iPhone application the first time: Reorienting the screen. With the Hello World application running, you can reorient the Simulator using Command-Left arrow and Command-Right arrow. Going home. Tap the Home button (Command-Shift-H) to leave the application and return to the SpringBoard home screen. Locking the “phone.” Hardware, Lock (Command-L) simulates locking the phone. n n n n n Viewing the console. In Xcode, choose Run, Console (Command-Shift-R) to view the Xcode console window.This window is where your printf, NSLog, and CFShow messages are sent by default. In the unlikely case where NSLog messages do not appear, use the Xcode organizer (Window, Organizer, Console) or open /Applications/Utilities/Console to view NSLog messages instead. Running Instruments. Use Run, Start with Performance Tool to select an Instruments template (such as Object Allocations or CPU Sampler) to use with the Simulator. Instruments monitors memory and CPU use as your application runs. Note Although the Organizer window offers direct access to crash logs, you’ll probably want to enable Developer Mode for Crash Reporter, too. This enables you to see trace backs immediately, without having to click Report all the time. To do this, open /Developer/Applications/Utilities/CrashReporterPrefs, select Developer, and quit. (Tip is courtesy of Emanuele Vulcano of infinite-labs.net.) Editing Identification Information The default Info.plist file enables you to create a working program but won’t, in its default state, properly handle iPhone provisioning, a necessary precondition for onphone application testing and distribution, which is discussed later in this chapter.The iPhone requires a signed identity, which you generate on Apple’s iPhone developer program site (http://developer.apple.com/iphone/program). For Simulator use only, you can double-click the Info.plist file to open it in a new window. Here, you’ll see the application identifier for your program, and you can edit just the company name entry.
Slide 49: 26 Chapter 1 Introducing the iPhone SDK Customization does not end with the Info.plist file. Close the Info and doubleclick InfoPlist.strings.This file is listed among your other project files. Edit "© __MyCompanyName__, 2008" to match the actual copyright you want to use for your program. Again choose File, Save (Command-S) to save your changes. Using the Debugger Xcode’s integrated debugger provides a valuable tool for iPhone application development. The following walk-through shows you where the debugger is and provides a few basic ways to use it with your program. In these steps, you’ll discover how to set breakpoints and use the debugger console to inspect program details. Set a Breakpoint Locate the loadView method in your Hello World program. Click in the leftmost Xcode window column, just to the left of the closing bracket. A blue breakpoint indicator appears (see Figure 1-5).The dark blue color means the breakpoint is active.Tap once to deactivate—the breakpoint turns light blue—and once more to reactivate.You can remove breakpoints by dragging them offscreen and add them by clicking in the column, next to any line of code. Figure 1-5 Blue breakpoint indicators appear in the leftmost Xcode window column. Run the Program Make sure the breakpoint is dark blue and that the button at the top of the Xcode screen says “Deactivate” (which means that the breakpoint is active) and run the program. The program will automatically stop when it hits the breakpoint and a red arrow point appears on top of the blue arrow. Open the Debugger Windows Choose Run, Debugger (Command-Shift-Y) to open the main debugger and Run, Console (Command-Shift-R) to open the console window. Figure 1-6 shows both windows.The debugger provides a graphical front end for inspecting program objects. The console offers a standard Gnu Debugger (gdb) command line.
Slide 50: Building Hello World 27 Figure 1-6 Xcode’s graphical debugger enables you to interactively inspect program state. A command-line version of gdb runs concurrently in the console window, as shown by the (gdb) prompt. A red arrow appears at the active breakpoint. Inspect Once stopped at the breakpoint, you can use the interactive debugger or the gdb com mand line to inspect objects in your program. For this example, navigate down the variable chain through Arguments, self, contentView, UIView,_viewFlags to confirm that the autoresizeMask has been properly set. Assuming Apple has not changed its constants, this mask should be 18, corresponding to 2 for flexible width and 16 for flexible height. Consider Other Breakpoint Options The breakpoint menu at the top of the Xcode window enables you to add customized breakpoint actions rather than use a generic break in execution. Figure 1-7 shows these options.To learn more about the Xcode debugger and its features, consult Apple’s Xcode User Guide: Debugging Programs. Figure 1-7 Use predefined breakpoint actions to automatically execute debugger actions.
Slide 51: 28 Chapter 1 Introducing the iPhone SDK Apple’s iPhone Developer Program You cannot run programs directly on the iPhone until you’ve entered Apple’s (paid) iPhone developer program.The program starts at $99 and allows you to develop iPhone applications as an individual ($99/year), a company ($99/year), or for in-house enterprise ($299/year). Apply at http://developer.apple.com/iphone/program. The iPhone uses code signing. Only properly signed applications are allowed to run on the iPhone. Once accepted into this program, you’ll be able to create a signing certificate that authenticates you as a developer and provision iPhones or iPod touch units for testing.The details for this program, for ad hoc distribution (for small controlled audiences of users), for the general provisioning process, and for access to Apple’s iPhone App Store remain in flux. Check with Apple for up-to-date information. Development Phones Development phones and iPods must be registered with Apple and provisioned through Xcode.When you’ve successfully joined the developer program and paid for your access, you’ll be able to use Apple’s program portal to obtain your certificates and register your units.The process is fussy. I urge you to follow Apple’s instructions exactly as you create development and distribution certificates and build provisioning profiles for your applicaions. t When you first tether your iPhone to your computer using a standard USB cable, Xcode detects your unit (see Figure 1-8). If you want to use your device for development, confirm that; otherwise click Ignore. A development unit needs to be devoted exclusively to development. Using a device as a development unit means that it is subject to onboard data changes and might no longer work reliably as a field unit. Figure 1-8 Xcode automatically detects new iPhones and iPod touches and offers to add them as development devices.
Slide 52: Apple’s iPhone Developer Program 29 Application Identifiers Apple uses two kinds of provisions: development provisions and distribution ones. Development provisioning allows you to download software to your iPhone for testing. Distribution provisions create applications suitable for App Store or ad hoc distribution. The iPhone lists its active provisions in Settings, General, Profile. To distribute applications on the iPhone, Apple requires that you register Application IDs at their site.To do this, you must be a registered team administrator. Use the Developer Program portal at Apple’s iPhone Dev Center. Use Program Portal, App IDs to enter the new ID, and then create a provisioning profile at Program, Provisioning. To develop applications, you can use specific application identifiers for on-phone testing or, better, create a single reverse domain wildcard com.mydomain.* application identifier that provisions all your applications for testing.This wildcard provision must match each application ID in your Info.plist file. I personally use com.sadun.*. Pick a reverse domain that describes your business or individual identity. After creating the wildcard provision at the program portal, download the new development provisioning profile. Back in Xcode, do the following: 1. Drag the mobileprovision file into your organizer. Alternatively, you can drag it onto the Xcode application icon. 2. Select Debug or Release from your project window. 3. In your project window’s Groups & Files list, open Targets and double-click your application name. A Target Info dialog opens. 4. Select Debug or Release in the Target Info window, matching whatever you selected in the project window. 5. Click the Properties tab. Enter your new application ID into the Identifier field. If you provisioned with a wildcard, enter the actual application name, not the wildcard (for example, com.mydomain.myapplication and not com.mydomain.*). 6. Click the Build tab. Set your Code Signing Identity to Any iPhone OS Device and iPhone Developer.This phrase is used to match the development certificate in your keychain.To check your keychain, open /Applications/Utilities/Keychain Access.The category My Certificates should contain at least one certificate containing iPhone Developer in its name. If you’ve signed up for distribution, you’ll likely have an iPhone distribution certificate, too. 7. Set your Code Signing Provision Profile to Any iPhone OS Device, and the name of the provision you just created for your application ID from the pop-up menu. (Do not select Default Provisioning Profile for Code Signing Identity.Your application will neither load to nor run on the iPhone.) After following these steps, you should be able to compile your application for the iPhone (Project, Set Active SDK, Device—iPhone OS), install it, and run it from the device itself. If you run into problems, consult Apple’s documentation and Developer Technical Support.
Slide 53: 30 Chapter 1 Introducing the iPhone SDK From Xcode to Your iPhone: The Organizer Interface Once added to Xcode, manage your development units using Xcode’s Organizer tool (Window, Organizer; Control-Command-O).This window (shown in Figure 1-9) forms the control hub for access between your development computer and your iPhone or iPod testbed.This window allows you to add and remove applications, view midtest console results, examine crash logs, and snap screenshots of your unit while testing your code. Here’s a quick rundown of the major features available to you through the Organizer console. Figure 1-9 The Xcode-based iPhone Organizer window (Window, Organizer) provides a single control hub for most of your application testing needs. Here, you can load firmware, install and remove applications, read through crash logs, snap device-based screenshots, and more. Projects and Sources List Keep your current projects in easy reach by dragging them onto the Organizer console. Once added, double-click the project name to open that project.You can add individual source files as well as complete projects. Use the Build, Clean, Run, and Action options at the top of the Organizer window, to perform even more development tasks directly from the Organizer.
Slide 54: From Xcode to Your iPhone: The Organizer Interface 31 Devices List The Devices list shows the name and status of those devices you’ve authorized as development platforms.The indicators to the right of each name show if the device is attached (green light) or not (red light). Summary Tab The Summary tab tells you the name, capacity, serial number, and identifier of your iPhone or iPod touch. Here is where you can provision your unit (that is, authorize it to work with the projects you build in Xcode), add and remove applications, and load the latest firmware. Each developer license allows you to provision up to five iPhones/iPod touches at a time for testing.The Provisioning list shows a list of application provisions available to your unit. Add a check to each provision you want to use.The provision determines which applications may or may not be run on the device. As a rule, distribution provisions are listed here (as are the development ones, but they are grayed out). A list of installed applications appears at the bottom of the Summary tab. Use the + and – buttons to add or remove applications. Open the disclosure triangle next to each application name to disclose the application data (the Documents and Library folders) associated with that application. Note Apple offers full instructions on how to provision your iPhone and create your personal signing certificates on its iPhone program portal pages. See http://developer.apple.com/ iphone/program. Console Tab Use the console to view system messages from your connected units.This screen shows NSLog() calls as you’re running software on the tethered iPhone. In addition to the debugging messages you add to your iPhone applications, you’ll also see system notices, device information, and debugging calls from Apple’s system software. It’s basically a textbased mess. Logged data also appears on the Xcode debugging console (Run, Console) along with any printf output. Crash Logs Tab Get direct access to your crash logs by selecting a particular crash (labeled with the iPhone application name and the date and time of the crash) from the screen’s leftmost column.The crash details, including thread information, exception types, and so forth, appear in the text view to the right of that column.
Slide 55: 32 Chapter 1 Introducing the iPhone SDK Screenshot Tab Snap your tethered iPhone’s screen by clicking the Capture button on the Screenshot tab.The screenshot feature takes a picture of whatever is running on the iPhone, whether your applications are open. So you can access shots of Apple’s built-in software and any other applications running on the iPhone. Once snapped, you can drag snapped images onto the desktop or save them as an open project’s new Default.png image. Archival shots appear in a library on the left side of the window. Select one and press the Delete key to permanently remove it. Note Screenshots are stored in your Application Support folder in Developer/Shared/Xcode/ Screenshots. About Tethering At this time, Apple provides no way to transfer, debug, or monitor applications wirelessly. That means you’ll do nearly all your work tethered over a standard iPhone USB cable. The physical reality of tethered debugging can be problematic. Reasons for this include the following points: When you unplug the cable, you unplug all the interactive debugging, console, and screenshot features. So you need to keep that cable plugged in all the time. You cannot reasonably use the iPhone with a dock. Sure, the dock is stable, but touching the screen while testing interfaces is extremely awkward when the iPhone is seated at a 75-degree angle. The tether comes to the bottom not the top of the unit, meaning it’s very easy to catch that cable and knock your iPhone to the floor. n n n Obviously, untethered testing would vastly improve many of these issues. Unfortunately, Apple has not yet introduced that option. If you like, you can Rube Goldberg-ize your iPhone to get around these problems. One solution is to attach Velcro to the back of an iPhone case—a case that leaves the bottom port connector open—and use that to stabilize your iPhone on your desk. It’s ugly, but it keeps your iPhone from getting knocked to the floor all the time. Testing Applications on Your iPhone Before you can test your application on the iPhone, you must first compile your source for the iPhone’s ARM processor and get that bundle copied over to your unit. Fortunately, Xcode allows you to easily choose whether to compile your iPhone application for the simulator or for a tethered device. Here are the steps to take:
Slide 56: From Xcode to Your iPhone: The Organizer Interface 33 1. Tether a provisioned iPhone to your Macintosh. 2. Choose Project, Set Active SDK, Device, and compile just as you did for the Simulator. Make sure you’ve provisioned the application (Target, Build, Code Signing Identity and Target, Build, Code Signing Provisioning Profile and have added a matching project identifier to Target, Properties, Identifier. 3. Compile your project and run it via Run, Go or Run, Run.These menu choices compile your program, preparing the application for the iPhone.Then they install and run it. 4. Wait. It takes a little time to compile, sign, sandbox, and install your application on an iPhone, especially with bigger project files and especially when you have several applications on your iPhone. It’s often a good chance to take a quick break as your program loads. After you’ve installed the application, it automatically launches, and if you’ve compiled with the debugger (Project, Set Active Build Configuration, Debug), the Gnu Debugger (gdb) opens in the Xcode debugging console window.The debugging functionality remains available to you until you quit the application.You can quit either through Xcode (typically by compiling a new version of the program and preparing to install it) or by pressing Home on the iPhone. Testing on the iPhone is vital. As simple and convenient as the Simulator is, it falls far short of the mark when it comes to a complete iPhone testing experience. At the time of writing, you cannot use the Simulator to test the onboard camera (see Chapter 7), keychain access (see Chapter 10), or accelerometer feedback (see Chapter 9, “People, Places, and Things”). And, of course, given that the iPhone is the target platform, it’s important that your software runs its best on its native system rather than on the Simulator.The iPhone itself offers the fully leaded un-watered-down testing platform, at least as far as a fully leaded sandboxed application with limited system read-and-write access will allow. Note SpringBoard learns about new and removed applications through two system notifications: com.apple.mobile.application_installed and com.apple.mobile.application_uninstalled. Xcode sends these notifications to a Darwin notification center, and SpringBoard listens in. Compiling for Distribution Submitting applications to App Store requires that you compile your program for distribution rather than development. Here’s a quick rundown of the steps you need to take: 1. Create a distribution certificate at the iPhone program portal. Download it to your Macintosh and add it to your keychain.You need do this only once. After creating a development or distribution certificate, it stays in your keychain regardless of the number of applications you build.
Slide 57: 34 Chapter 1 Introducing the iPhone SDK 2. If you haven’t done so already, register a wildcard application identifier at the program portal. 3. Create a distribution provisioning profile for that wildcard application identifier. Name it with an easy-to-identify name (for example, My Wildcard Distribution Profile). Download it and add it to Xcode by dropping it onto the Xcode application icon or into the Organizer window. 4. Open the Project Info window (Command-I). In the Configurations tab, select Release. Click Duplicate and rename the new copy to Distribution.This new distribution configuration will store all the information you need for creating an App Store–compatible build. Once created, you can switch between the Debug, Release, and Distribution profiles, and they’ll remember their settings. Just be aware that you need to set the configuration in two places: on the main project window and in the Target Info window, as you’re about to see. 5. Close the Project Info window. Select Distribution from the Active Build Configuration pop-up in the main project window (Figure 1-1).This is the first of two places that you’ll set the build configuration. 6. Open the Target Info window (double-click Targets, Project Name in the main project window) and select the Build tab. 7. In the Target Info, Build window, select Distribution from the Configuration popup.This is the second required configuration setting. 8. Under Code Signing Identity, change iPhone Developer to iPhone Distribution. 9. Select the new wildcard distribution profile from the Code Signing Provisioning Profile pop-up. 10. Build your project.Then, choose Groups & Files,Project Name, Products, Application Name, Reveal in Finder to find the newly created application bundle. These steps enable you to build a distribution version of your program. After building your project, you can then zip up the new bundle and submit it to App Store. Using Undocumented API Calls Officially, Apple prohibits the use of undocumented API calls. If you want your application to conform to the App Store restrictions, restrain from using any unpublished items. Unofficially, Apple’s policy has always been that you can use any API call in public frameworks as long as you accept the risk that your program may stop working when Apple releases new operating system updates.This unofficial policy currently crosses over to the iPhone. If an item appears in a public framework, you may use it at your own risk. That spirit of open access informs this book. Undocumented calls appear throughout, particularly in Chapter 4, “Alerting Users.” Every use is marked.You will not find a recipe that uses an undocumented call without it being stated explicitly.
Slide 58: Ad Hoc Distribution 35 At the same time, this book does not cross certain lines.The rules for book samples are as follows: Private frameworks are private. You may link to and access only those public items that appear in the Apple-sanctioned Frameworks folder. You don’t run daemons. All code executes in the primary application. You must quit when the iPhone says so. The code respects Apple’s one application at a time policy. You cannot use plug-ins or execute arbitrary code. Apple and App Store approve all code. The sandbox is the sandbox. Nothing in this book shows you how to access private areas such as the onboard iTunes Media folder. n n n n n Courteous computing doesn’t mean limited computing. If you’d rather avoid undocumented API calls—and I know a large number of readers will—the remaining majority of tricks and tips throughout this book will still allow you to add excitement and novelty into your iPhone development experience. Ad Hoc Distribution Apple allows you to distribute your applications outside the App Store via Ad Hoc distribution.With Ad Hoc, you can send your applications to up to 100 registered devices and run those applications using a special kind of mobile provision that allows the applications to execute under the iPhone’s FairPlay restrictions. Ad Hoc distribution is especially useful for beta testing and for submitting review applications to news sites and magazines. Start by registering your device. Use the iPhone Developer Program Portal to register device identifiers (Program Portal, Devices). Recover these identifiers from the iPhone directly (use the UIDevice calls from Chapter 9), from iTunes (click on the word Serial Number in the iPhone’s summary tab), or from System Profiler (select USB, iPhone, Serial Number). Enter the identifier and a unique username. Next, build your provision.To build a mobile provision, select Program Portal, Provisioning, Distribution. Click Add Profile. Select Ad Hoc, enter a profile name, your standard wildcard Application identifier (for example, com.yourname.*), and select the device or devices to deploy on. Click Submit and wait for Apple to build the new mobile provision. Download the provision file. Drop it onto Xcode.You will use it to build your application. You need to include a special entitlement file in Ad Hoc projects. In Xcode, choose File, New File, Code Signing, Entitlements. Click Next. Create a new entitlement called dist.plist. Click Finish.The entitlement property list appears in the Products folder. Double-click it to open and uncheck get-task-allow. (That is, set it to a Boolean value of FALSE.)
Slide 59: 36 Chapter 1 Introducing the iPhone SDK After setting up your entitlement, you need to add it to your target settings. Select your Distribution configuration from the project window. Double-click the project target, (Targets > Your Project Name).The Target Info window opens. In the Build tab, set your configuration again to Distribution if it is not already set. Double-click Code Signing Entitlements. Add the filename dist.plist to the Code Signing Entitlement and click OK. Now you’re ready to build your application. Make sure your Code Signing Identity is set to iPhone Distribution. Select your new ad-hoc mobile provision from the Any iPhone OS Device pop-up. Select Build, Clean (Command-Shift-K) and then Build, Build (Command-B) your project. Select the newly compiled product from the Products folder in the project window. Right-click it and choose Reveal in Finder. A Finder window opens, showing the compiled item. Distribute a copy of this application, which you just compiled with the mobile ad hoc provision, along with the provision itself that you downloaded from Apple.Your user can drop the provision and the application into iTunes before syncing your application to his or her iPhone.The application will run only on those phones you registered, providing a secure way to distribute these apps directly to your user. Summary This chapter has introduced you to the iPhone application, how it is built, and how you can build your own basic Hello World utility using just a few steps. Here are some things you may want to take away with you before leaving this chapter: Downloading and installing the SDK and building and testing your first application shouldn’t take you more than a few hours to do based on your download speed. The SDK is over a gigabyte in size, but once downloaded it’s really easy to create your first application. The iPhone application bundle is much simpler and less structured than its Macintosh brother, although it shares many common features, including Info.plist and lproj folders. Unfortunately, the iPhone SDK requires you to test only on a tethered device. WiFi testing is not yet available. Despite that, the Organizer in Xcode provides a superb organizer for testing your applications with its console, crash logs, and screenshots. n n n n If you come from a Cocoa background, you’ll be prepared if not overprepared to create iPhone applications. Familiarity with Objective-C and Cocoa best practices will put you on a firm development footing.
Slide 60: 2 Views Pretty muchthat you canthat appears oncolors, pictures, and buttons.You canact like everything the iPhone’s screen is a view.Views little canvases draw on with drag them around the screen.You can resize them.You can layer them. In this chapter, you discover how to design and build screen content using Cocoa Touch and UIViews.You learn about view hierarchy, geometry, and animation, and find out how to combine event feedback from UITouches into meaningful UIView responses.There’s so much that UIViews can do that a single chapter has no hope of covering the entire class with the thoroughness it deserves. Instead, this chapter introduces essential functionality and recipes that you can use as a starting point for your own UIView exploration. UIView and UIWindow The iPhone rule goes like this: one window, many views. If you keep that idea in mind, the iPhone interface design scenario simplifies. Metaphorically speaking, UIWindow is the TV set, and UIViews are the actors on your favorite show.They can move around the screen, appear, and disappear, and may change the way they look and behave over time. The TV set, on the other hand, normally stays still. It has a set screen size that doesn’t change even if the virtual world you see through it is practically unlimited.You may even own several TVs in the same household (just like you can create several UIWindow instances in the same application), but you can watch just one at a time. UIViews are GUI building blocks.They provide visual elements that are shown onscreen and invite user interaction. Every iPhone user interface is built from UIViews displayed within one UIWindow, which is itself a specialized kind of UIView.The window acts a container; it is the root of the display hierarchy. It holds all the visible application components within itself.The following sections will give you just a taste of the kind of ways you can control and manipulate views, their hierarchy, and their geometry. Hierarchy A tree-based hierarchy orders what you see on your iPhone screen. Starting with the main window, views are laid out in a specifically hierarchical way. All views may have
Slide 61: 38 Chapter 2 Views children, called subviews. Each view, including the root window, owns an ordered list of these subviews.Views might own many subviews; they might own none.Your application determines how views are laid out and who owns whom. Subviews display onscreen in order, always from back to front. And because the iPhone supports view transparency, this works exactly like a stack of animation cells—those transparent sheets used to create cartoons. Only the parts of the sheets that have been painted are shown.The clear parts allow any visual elements behind that sheet to be seen. Figure 2-1 shows a little of the layering used in a typical window. Here you see the window that owns a UINavigationController-based window.The window (represented by the clear, rightmost element) owns a Navigation subview, which in turn owns two subview buttons (one left and one right) and a table.These items stack together to build the GUI. Figure 2-1 Adding subview hierarchies allows you to build complex GUIs. Notice how the buttons appear over the navigation bar and how the table is sized so that it won’t obscure either the buttons or bar.The button frames are small, taking up very little space onscreen.The table frame is large, occupying the majority of screen space. Here are some ways you can manage subviews in your programs: To add a subview, use a call to [parentView addSubview:child]. Newly added subviews are always frontmost on your screen. Query any view for its children by asking it for [parentView subviews].This returns an array of views, ordered from back to front. n n
Slide 62: UIView and UIWindow 39 n n n Remove a subview from its parent with [childView removeFromSuperview]. Reorder subviews using [parentView exchangeSubviewAtIndex:i withSubviewAtIndex:j]. Move subviews to the front or back using bringSubviewToFront: or sendSubviewToBack:. Tag your subviews using setTag:.This identifies views by tagging them with a number. Retrieve that view from the child hierarchy by calling viewWithTag: on the parent. Note You can tag any instance that is a child of UIView, including windows and controls. So if you have many onscreen buttons and switches, for example, add tags so that you can tell them apart when users trigger them. Geometry and Traits Every view uses a frame to define its boundaries.The frame specifies the outline of the view: its location, width, and height.You define the frame rectangle using Core Graphics structures. For frames, this usually means a CGRect rectangle made up of an origin (a CGPoint, x and y) and a size (a CGSize, width and height). Here are some quick facts about these types. CGRect The CGRect structure defines an onscreen rectangle. It contains an origin (rect.origin) and a size (rect.size).These are CGRect functions you’ll want to be aware of: n CGRectMake() method()(origin.x, origin.y, size.width, size.height) Defines rectangles in your code. NSStringFromCGRect()converts() method() A CGRect structure to a format- n ted string. n CGRectFromString()recovers() method() A rectangle from its string repre- sentation. n CGRectInset() enables() method() You to create a smaller or larger a rectangle n n that’s centered on the same point. Use a positive inset for smaller rectangles, negative for larger ones. CGRectIntersectsRect() lets() method() You know whether rectangle structures intersect. Use this function to know when two rectangular onscreen objects overlap. CGRectZero is() method() A rectangle constant located at (0,0) whose width and height are zero.You can use this constant when you’re required to create a frame but you’re still unsure what that frame size or location will be at the time of creatione. CGPoint and CGSize Points refer to locations defined with x and y coordinates; sizes have width and height. Use CGPointMake() method (x, y) to create points. CGSizeMake(width, height)
Slide 63: 40 Chapter 2 Views creates sizes. Although these two structures appear to be the same (two floating-point values), the iPhone SDK differentiates between them. Points refer to locations. Sizes refer to extents.You cannot set myFrame.origin to a size. As with rectangles, you can convert them to and from strings: NSStringFromCGPoint(), NSStringFromCGSize(), CGSizeFromString(), and CGPointFromString() perform these functions. Defining Locations You can define a view’s location by setting its center (which is a CGPoint) or bounds (CGRect). Unlike the frame, a view’s bounds reflect the view’s frame in its own coordinate system. In practical terms, that means the origin of the bounds is (0.0, 0.0), and its size is its width and height. When you want to move or resize a view, update its frame’s origin, center, or size.You don’t need to worry about things such as rectangular sections that have been exposed or hidden.The iPhone takes care of the redrawing.This lets you treat your views like tangible objects and delegate the rendering issues to Cocoa Touch. For example [myView setFrame:CGRectMake(0.0f, 50.0f, mywidth, myheight)]; Transforms Standard Core Graphics calls transform views in real time. For example, you can apply clipping, rotation, or other 2D geometric effects. Cocoa Touch supports an entire suite of affine transforms (translate, rotate, scale, skew, and so on).The drawRect: method for any UIView subclass provides the entry point for drawing views through low-level Core Graphics calls. Note When calling Core Graphics functions, keep in mind that Quartz lays out its coordinate system from the bottom left, whereas UIViews have their origin at the top left. Other View Traits In addition to the physical screen layout, you can set the following view traits among others: n n Every view has a translucency factor (alpha) that ranges between opaque and transparent. Adjust this by issuing [myView setAlpha:value], where the alpha values falls between 0.0 (fully transparent) and 1.0 (fully opaque). You can assign a color to the background of your view. [myView setBackgroundColor:[UIColor redColor]] colors your view red. View Layout Figure 2-2 shows the layout of a typical iPhone application screen. For current releases of the iPhone, the screen size is 320x480 pixels in portrait mode, 480x320 pixels in landscape. At the top of the screen, whether in landscape or portrait mode, a standard status bar
Slide 64: UIView and UIWindow 41 occupies 20 pixels of height.To query the status bar frame, call [[UIApplication sharedApplication] statusBarFrame]. If you’d rather free up those 20 pixels of screen space for other use, you can hide the status bar entirely. Use this UIApplication call: [UIApplication sharedApplication] setStatusBarHidden:YES animated:NO]. Alternatively, set the UIStatusBarHidden key to <true/> in your application Info.plist file. To run your application in landscape-only mode, set the status bar orientation to landscape. Do this even if you plan to hide the status bar (that is, [[UIApplication sharedApplication] setStatusBarOrientation: UIInterfaceOrientationLandscapeRight]).This forces windows to display side to side and produces a proper landscape keyboard. The UIScreen object acts as a stand in for the iPhone’s physical screen ([UIScreen mainScreen]).The screen object maps view layout boundaries into pixel space. It returns either the full screen size (bounds) or just the rectangle that applies to your application (applicationFrame).This latter takes the size of your status bar and, if used, any toolbars/navigation bars into account. By default, UINavigationBar, UIToolbar, and UITabBar objects are 44 pixels in height each. Use these numbers to calculate the available space on your iPhone screen and lay out your application views when not using Interface Builder’s layout tools. Figure 2-2 On current generations of the iPhone, the status bar is 20 pixels high, often followed below by a 44-pixel-high navigation bar. If you use a toolbar at the bottom of your screen, that will also occupy 44 pixels. It helps to use Photoshop or some other image layout program to design your screens taking these geometries into account.
Slide 65: 42 Chapter 2 Views Gestures Views intercept user touches.This integration between the way things look and the way things react enables you to add a meaningful response to taps, drags, and what have you. Adding touch handlers like touchesBegan: withEvent: to your views allows you to intercept user touches, determine the phase of the touch (the equivalent of mouse down, mouse dragged, mouse up), and produce feedback based on those touches. The UITouch class tells you where the event took place (locationInView:) and the tap count (tapCount), which is vital for distinguishing between single- and double-taps. Several recipes in this chapter demonstrate how to use these gesture responses and how to integrate view geometry and hierarchy into your applications for enticing, layered, direct-manipulation interfaces. Recipe: Adding Stepwise Subviews Expand your view hierarchy by calling addSubview:.This adds a subview to some other view. Recipe 2-1 shows a simple UIViewController’s loadView method that defines a series of stepped subviews. It demonstrates the basics of allocating, framing, and adding views. These subviews are not nested, in that they all belong to the same parent.They’re indented so that you can see them all at once.The indentation uses the handy CGRectInset() function. Pass it a rectangle (using the CGRect structure) and two insets—horizontal and vertical—and it returns the inset, centered rectangle. Here, each subview is inset from its parent or sibling’s frame by 32 pixels on each side. In their simplest form, views are little more than transparent placeholders. Coloring the view backgrounds distinguishes one view from another in the absence of meaningful content (see Figure 2-3). It’s a useful trick when trying to test layouts before committing to an actual design. Always keep your coordinate system in mind.When working with view hierarchy, you must define a view’s frame in its parent’s coordinate system.The example in Recipe 2-1 requests the application frame to lay out the main view and then resets its origin to (0, 0). Resetting the origin updates the frame from the screen’s to the main view’s coordinate system.This reset forms the basis for the view layout that follows. Recipe 2-1 Adding Nested Subviews - (void)loadView { // Create the main view CGRect appRect = [[UIScreen mainScreen] applicationFrame]; contentView = [[UIView alloc] initWithFrame:appRect]; contentView.backgroundColor = [UIColor whiteColor]; // Provide support for autorotation and resizing contentView.autoresizesSubviews = YES; contentView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | ➥UIViewAutoresizingFlexibleHeight);
Slide 66: Recipe: Adding Stepwise Subviews 43 Recipe 2-1 Continued self.view = contentView; [contentView release]; // reset the origin point for subviews. The new origin is 0,0 appRect.origin = CGPointMake(0.0f, 0.0f); // Add the subviews, each stepped by 32 pixels on each side UIView *subview = [[UIView alloc] initWithFrame:CGRectInset(appRect, 32.0f, ➥32.0f)]; subview.backgroundColor = [UIColor lightGrayColor]; [contentView addSubview:subview]; [subview release]; subview = [[UIView alloc] initWithFrame:CGRectInset(appRect, 64.0f, 64.0f)]; subview.backgroundColor = [UIColor darkGrayColor]; [contentView addSubview:subview]; [subview release]; subview = [[UIView alloc] initWithFrame:CGRectInset(appRect, 96.0f, 96.0f)]; subview.backgroundColor = [UIColor blackColor]; [contentView addSubview:subview]; [subview release]; } Figure 2-3 The code in Recipe 2-1 defines a UIView controller’s main view with three colored, nested subviews.
Slide 67: 44 Chapter 2 Views Reorienting Extending Recipe 2-1 to enable orientation changes takes thought.You cannot just swap each subview’s heights and widths as you might assume.That’s because the shapes of horizontal and vertical applications on the iPhone use different aspect ratios. Assuming a 20-pixel status bar, portrait view areas are 320 pixels wide by 460 pixels high; landscapes are 480 pixels wide by 300 pixels high (refer to Figure 2-2).This difference throws off interfaces that depend solely on rotation to reorient. To rotate this example, add code that distinguishes landscape orientations from portrait ones and adjust the frames accordingly.This is shown in Recipe 2-2. Avoid reorientation schemes that rely on toggling (for example, “I was just in portrait mode so, if the orientation changed, I must be in landscape mode.”) It’s entirely possible to switch from left-landscape to right-landscape without hitting a portrait state inbetween. Orientation is all about sensors and feedback, and the iPhone is not guaranteed to catch any middle state between two orientations. Fortunately, UIKit provides a UIViewController callback that alerts you to new orientations and that specifies what that orientation will be. Recipe 2-2 Adding Reorientation Support to the Preceding Subview Example - (void)willRotateToInterfaceOrientation: (UIInterfaceOrientation)orientation duration:(NSTimeInterval)duration { CGRect apprect; apprect.origin = CGPointMake(0.0f, 0.0f); // adjust the frame size based on actual orientation if ((orientation == UIInterfaceOrientationLandscapeLeft) || ➥(orientation == UIInterfaceOrientationLandscapeRight)) apprect.size = CGSizeMake(480.0f, 300.0f); else apprect.size = CGSizeMake(320.0f, 460.0f); // resize each subview accordingly float offset = 32.0f; for (UIView *subview in [contentView subviews]) { CGRect frame = CGRectInset(apprect, offset, offset); [subview setFrame:frame]; offset += 32.0f; } } // Allow the view to respond to iPhone Orientation changes -(BOOL)shouldAutorotateToInterfaceOrientation: (UIInterfaceOrientation)interfaceOrientation
Slide 68: Recipe: Dragging Views 45 Recipe 2-2 { Continued return YES; } Recipe: Dragging Views Cocoa Touch simplifies direct view manipulation.When dealing with many onscreen views, the iPhone takes charge of deciding which view the user touched and passes any touch events to the proper view for you.This helps you write concrete direct-manipula tion interfaces where users touch, drag, and interact with onscreen objects. Recipe 2-3 centers on touches in action.This example creates a child of UIImageView called DragView that enables users to drag the view around the iPhone screen. Being an image view, it’s important to enable its user interaction, via [dragger setUserInteractionEnabled:YES].This holds true for backdrops as well as directinteraction views.Whenever working with UIImageView in direct-manipulation interfaces, make sure to enable interaction, no matter what role in the view hierarchy.With image views, the user interaction toggle affects all the view’s children as well as the view itself. When a user first touches any DragView (see the flowers in Figure 2-4), the object stores the start location as an offset from the view’s origin. As the user drags, the view moves along with the finger—always maintaining the same origin offset so that the movement feels natural. Figure 2-4 The code in Recipe 2-3 creates an interface with 16 flowers that can be dragged around the iPhone screen.
Slide 69: 46 Chapter 2 Views Note The way the example in Figure 2-4 is built, you can use multiple fingers to drag more than one flower around the screen at once. It’s not multitouch per se because each flower (UIView) responds to only one touch at a time. A discussion of true multitouch interaction follows later in this chapter. Touching an object also does one more thing in this code: It pops that object to the front of the parent view.This means any dragged object always floats over any other object onscreen. Do this by telling the view’s parent (its superview) to bring the view to its front. UITouch The UITouch class defines how fingers move across the iPhone screen.Touches are sent while invoking the standard began, moved, and ended handlers.You can also query user events (of the UIEvent class) to return touches affecting a given view through touchesForView: and touchesForWindow:.These calls return an unordered set (NSSet) of touches. Note Send allObjects to any NSSet to return an array of those objects. A touch tells you several things: where the touch took place (both the current and most recent previous location), what stage of the touch was used (essentially mouse down, mouse moved, mouse up), a tap count (for example, single-tap/double-tap), when the touch took place (through a time stamp), and so forth. For nonmultitouch interaction styles, assume that you’re dealing with a single touch at any time.The code in Recipe 2-3 recovers the first available touch for each event by calling anyObject on the returned touch set. Recipe 2-3 /* * */ Building Multiple Draggable Views DragView: Draggable views @interface DragView : UIImageView { CGPoint startLocation; } @end @implementation DragView // Note the touch point and bring the touched view to the front - (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event
Slide 70: Recipe: Dragging Views 47 Recipe 2-3 { Continued CGPoint pt = [[touches anyObject] locationInView:self]; ➥startLocation = pt; [[self superview] bringSubviewToFront:self]; } // As the user drags, move the flower with the touch - (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event { CGPoint pt = [[touches anyObject] locationInView:self]; CGRect frame = [self frame]; frame.origin.x += pt.x - startLocation.x; frame.origin.y += pt.y - startLocation.y; [self setFrame:frame]; } @end /* * Hello Controller: The primary view controller */ @interface HelloController : UIViewController { UIView *contentView; } @end @implementation HelloController #define MAXFLOWERS 16 CGPoint randomPoint() {return CGPointMake(random() % 256, random() % 396);} - (void)loadView { // Create the main view with a black background CGRect apprect = [[UIScreen mainScreen] applicationFrame]; contentView = [[UIView alloc] initWithFrame:apprect]; contentView.backgroundColor = [UIColor blackColor]; self.view = contentView; [contentView release]; // Add the flowers to random points on the screen for (int i = 0; i < MAXFLOWERS; i++) {
Slide 71: 48 Chapter 2 Views Recipe 2-3 Continued CGRect dragRect = CGRectMake(0.0f, 0.0f, 64.0f, 64.0f); dragRect.origin = randomPoint(); DragView *dragger = [[DragView alloc] initWithFrame:dragRect]; [dragger setUserInteractionEnabled:YES]; // select random flower color NSString *whichFlower = [[NSArray arrayWithObjects:@"blueFlower.png", ➥@"pinkFlower.png", @"orangeFlower.png", nil] objectAtIndex:(random() % ➥3)]; [dragger setImage:[UIImage imageNamed:whichFlower]]; // add the new subview [contentView addSubview:dragger]; [dragger release]; } } -(void) dealloc { [contentView release]; [super dealloc]; } @end Adding Persistence Persistence represents a key iPhone design touch point. After users leave a program, Apple strongly recommends that they return to a state that matches as closely to where they left off as possible. Adding persistence to this sample code involves several steps: 1. Storing the data 2. Resuming from a saved session 3. Providing a startup image that matches the last session Storing State Every view knows its position because you can query its frame.This enables you to recover and store positions for each onscreen flower.The flower type (green, pink, or blue) is another matter. For each view to report its current flower, the DragView class must store that value, too. Adding a string instance variable enables the view to return the image name used. Listing 2-1 shows the extended DragView class definition. Listing 2-1 { CGPoint startLocation; The Updated DragView Class Includes a String to Store the Flower Type @interface DragView : UIImageView
Slide 72: Recipe: Dragging Views 49 Listing 2-1 Continued NSString *whichFlower; } @property (nonatomic, retain) NSString *whichFlower; @end Adding this extra variable enables the HelloController class to store both a list of colors and a list of locations to its defaults file. A simple loop collects both values from each draggable view and then stores them. Listing 2-2 presents an updateDefaults method, as defined in HelloController.This method saves the current state to disk. It should be called in the application delegate’s applicationWillTerminate: method, just before the program ends. Notice the use here of NSStringFromCGRect(). It provides a tight way to store frame information as a string.To recover the rectangle, issue CGRectFromString(). Each call takes one argument: a CGRect in the first case, an NSString * in the second. The UIKit framework provides calls that translate points and sizes as well as rectangles to and from strings. Defaults, as you can see, work like a dictionary. Just assign an object to a key and the iPhone “automagically” updates the preferences file associated with your application ID. Your application ID is defined in Info.plist. Defaults are stored in Library/Preferences inside your application’s sandbox. Calling the synchronize function updates those defaults immediately instead of waiting for the program to terminate. Listing 2-2 Storing Flower Locations via User Defaults // Collect all the colors and locations and save them for the next use - (void) updateDefaults { NSMutableArray *colors = [[NSMutableArray alloc] init]; NSMutableArray *locs = [[NSMutableArray alloc] init]; for (DragView *dv in [contentView subviews]) { [colors addObject:[dv whichFlower]]; [locs addObject:NSStringFromCGRect([dv frame])]; } [[NSUserDefaults standardUserDefaults] setObject:colors forKey:@"colors"]; [[NSUserDefaults standardUserDefaults] setObject:locs forKey:@"locs"]; [[NSUserDefaults standardUserDefaults] synchronize]; [colors release]; [locs release]; }
Slide 73: 50 Chapter 2 Views Recovering State Persistence awareness generally resides in the view controller’s init or loadView (for example, before the view actually appears).These methods should find any previous state information and, for this example, match the flowers to that state.When querying user defaults, this code checks whether state data is unavailable (for example, the value returned is nil).When state data goes missing, the method creates random flowers at random points. Listing 2-3 shows a state-aware version of loadView. Note When working with large data sources, you may want to initialize and populate your saved object array in the UIViewController‘s init method, and then draw them in loadView. Where possible, use threading when working with many objects to avoid blocking. Listing 2-3 Checking for Previous State - (void)loadView { // Create the main view CGRect apprect = [[UIScreen mainScreen] applicationFrame]; contentView = [[UIView alloc] initWithFrame:apprect]; contentView.backgroundColor = [UIColor blackColor]; self.view = contentView; // Attempt to read in previous colors and locations NSMutableArray *colors, *locs; colors = [[NSUserDefaults standardUserDefaults] objectForKey:@"colors"]; locs = [[NSUserDefaults standardUserDefaults] objectForKey:@"locs"]; for (int i = 0; i < MAXFLOWERS; i++) { // Use a random point unless there’s a previous location CGRect dragRect = CGRectMake(0.0f, 0.0f, 64.0f, 64.0f); dragRect.origin = randomPoint(); if (locs && ([locs count] == MAXFLOWERS)) ➥dragRect = CGRectFromString([locs objectAtIndex:i]); DragView *dragger = [[DragView alloc] initWithFrame:dragRect]; [dragger setUserInteractionEnabled:YES]; // Use a random color unless there’s a previous color NSString *whichFlower = [[NSArray arrayWithObjects:@"blueFlower.png", ➥@"pinkFlower.png", @"orangeFlower.png", nil] objectAtIndex:(random() ➥% 3)]; if (colors && ([colors count] == MAXFLOWERS)) ➥whichFlower = [colors objectAtIndex:i]; [dragger setWhichFlower:whichFlower]; [dragger setImage:[UIImage imageNamed:whichFlower]];
Slide 74: Recipe: Clipped Views 51 Listing 2-3 Continued // Add the subview [contentView addSubview:dragger]; [dragger release]; } } Startup Image Apple has not yet included persistence screenshot capabilities into its official SDK release, although the functionality is partially available in the UIKit framework as an undocumented call.To access the _writeApplicationSnapshot feature shown in Listing 2-4, you must add it by hand to the UIApplicationClass interface. Once added, you can build a cached shot of your screen before ending the application. Note See Chapter 1, “Introducing the iPhone SDK,” for further discussion about using undocumented calls and features in your programs. The idea is this:When you leave the application, you snap a picture of the screen. Then when your application starts up (presumably returning you to the same state you left with), the cached image acts as the Default.png image, giving the illusion that you’re jumping directly back without any startup sequence. Apple has yet to enable this feature with the iPhone SDK, and at the time of writing, applications cannot check in to find updated snapshots. Hopefully, Apple will provide this functionality in a future firmware release. Listing 2-4 Screenshotting Before Application Termination @interface UIApplication (Extended) -(void) _writeApplicationSnapshot; @end [[UIApplication sharedApplication] _writeApplicationSnapshot]; Recipe: Clipped Views When working with direct-manipulation interfaces, it’s unlikely that you’ll want to deal solely with rectangular views. Soft borders, rounded corners, and other visual enhancements are easily added to UIView instances. Clipping creates view shapes that fill only part of a view’s frame.You can produce clipping with Core Graphics using the drawRect: method of a UIView object, just as
Slide 75: 52 Chapter 2 Views you would on a Macintosh. Core Graphics enables you to build paths from sources including points, lines, standard shapes (such as ellipses), and Bézier curves. Clipping your views to these paths creates the illusion of nonrectangular onscreen objects. Figure 2-5 shows a number of onscreen circular clipped views, clearly overlapping with each other. These views were created by the code shown in Listing 2-5.This code creates a path, performs the clipping, and then draws into the clipped view. Figure 2-5 Clipping enables you to create nonrectangular views onscreen from rectangular source material, using rectangular UIView frames. Listing 2-5 Clipping a View to a Circular Path - (void) drawRect: (CGRect) aRect { CGRect bounds = CGRectMake(0.0f, 0.0f, SIDELENGTH, SIDELENGTH); // Create a new path CGContextRef context = UIGraphicsGetCurrentContext(); CGMutablePathRef path = CGPathCreateMutable(); // Add circle to path CGPathAddEllipseInRect(path, NULL, bounds); CGContextAddPath(context, path);
Slide 76: Recipe: Clipped Views 53 Listing 2-5 Continued // Clip to the circle and draw the logo CGContextClip(context); [logo drawInRect:bounds]; CFRelease(path); } Balancing Touches with Clipping Visual clipping does not affect how UIViews respond to touches.The iPhone senses user taps throughout the entire view frame.This includes the undrawn area such as the corners of the frame outside the actual circles of Figure 2-5 just as much as the clipped presentation.That means that unless you add some sort of hit test, users may attempt to tap through to a view that’s “obscured” by the clear portion of the UIView frame. Listing 2-6 adds a simple hit test to the clipped views, determining whether touches fall within the clipping path. I implemented circular clipping and circular hit tests to provide the simplest example. Use any computable test method you like to determine whether a user touch intersects the view. Add pointInside:withEvent: to your UIView subclass and return YES when the touch has properly hit your view or NO when it does not. Listing 2-6 Checking Circular Views against Touches - (BOOL) pointInside:(CGPoint)point withEvent:(UIEvent *)event { CGPoint pt; float HALFSIDE = SIDELENGTH / 2.0f; // normalize with centered origin pt.x = (point.x - HALFSIDE) / HALFSIDE; pt.y = (point.y - HALFSIDE) / HALFSIDE; // x^2 + y^2 = hypoteneus length float xsquared = pt.x * pt.x; float ysquared = pt.y * pt.y; // If the length < 1, the point is within the clipped circle if ((xsquared + ysquared) < 1.0) return YES; return NO; }
Slide 77: 54 Chapter 2 Views Accessing Pixel-by-Pixel Values There are many ways to test user touches against views. Listing 2-6 computed whether a touch fell within a circle’s radius.With hit masks and variable transparency images, you can test against a point’s alpha value.Translucency controls whether you trigger a response. Listing 2-7 extends the UIImageView class to add an image’s bitmap representation. It tests touches against alpha values in the bitmap, point by point. Pixels whose alpha levels fall below 0.5 will not respond to touches using this code. Note The code in this listing returns a bitmap context, and its bitmap data is based on Apple sample code. Listing 2-7 Testing Touch Hits Against a Bitmap // Return a bitmap context using alpha/red/green/blue byte values CGContextRef CreateARGBBitmapContext (CGImageRef inImage) { CGContextRef context = NULL; CGColorSpaceRef colorSpace; void * bitmapData; int bitmapByteCount; int bitmapBytesPerRow; size_t pixelsWide = CGImageGetWidth(inImage); size_t pixelsHigh = CGImageGetHeight(inImage); bitmapBytesPerRow = (pixelsWide * 4); bitmapByteCount = (bitmapBytesPerRow * pixelsHigh); colorSpace = CGColorSpaceCreateDeviceRGB(); if (colorSpace == NULL) { fprintf(stderr, "Error allocating color space\n"); return NULL; } // allocate the bitmap & create context bitmapData = malloc( bitmapByteCount ); if (bitmapData == NULL) { fprintf (stderr, "Memory not allocated!"); CGColorSpaceRelease( colorSpace ); return NULL; }
Slide 78: Recipe: Clipped Views 55 Listing 2-7 Continued context = CGBitmapContextCreate (bitmapData, pixelsWide, pixelsHigh, 8, ➥bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedFirst); if (context == NULL) { free (bitmapData); fprintf (stderr, "Context not created!"); } CGColorSpaceRelease( colorSpace ); return context; } // Return Image Pixel data as an ARGB bitmap unsigned char *RequestImagePixelData(UIImage *inImage) { CGImageRef img = [inImage CGImage]; CGSize size = [inImage size]; CGContextRef cgctx = CreateARGBBitmapContext(img, size); if (cgctx == NULL) return NULL; CGRect rect = {{0,0},{size.width, size.height}}; CGContextDrawImage(cgctx, rect, img); unsigned char *data = CGBitmapContextGetData (cgctx); CGContextRelease(cgctx); return data; } // Create an Image View that stores a copy of its image as an addressable bitmap @interface BitMapView : UIImageView { unsigned char *bitmap; CGSize size; UIView *colorView; } @end @implementation BitMapView // Hit test relies on the alpha level of the touched pixel - (BOOL) pointInside:(CGPoint)point withEvent:(UIEvent *)event { long startByte = (int)((point.y * size.width) + point.x) * 4; int alpha = (unsigned char) bitmap[startByte]; return (alpha > 0.5); }
Slide 79: 56 Chapter 2 Views Listing 2-7 Continued -(void) setImage:(UIImage *) anImage { [super setImage:anImage]; bitmap = RequestImagePixelData(anImage); size = [anImage size]; } @end Recipe: Detecting Multitouch By enabling multitouch interaction in your UIViews, the iPhone enables you to recover and respond to multifinger interaction.This recipe, shown in Recipe 2-4, demonstrates how to add multitouch to your iPhone applications. To begin, set multipleTouchEnabled to YES or override isMultipleTouchEnabled for your view.This tells your application to poll for more than one UITouch at a time. Now when you call touchesForView:, the returned set may contain several touches. Use NSSet’s allObjects method to convert that set into an addressable NSArray.When the array’s count exceeds one, you know you’re dealing with multitouch. In theory, the iPhone could support an arbitrary number of touches. In practice, multitouch is limited to five finger touches at a time. Even five at a time goes beyond what most developers need.There aren’t many meaningful gestures you can make with five fingers at once.This particularly holds true when you grasp the iPhone with one hand and touch with the other. Perhaps it’s a comfort to know that if you need to, the extra finger support has been built in. Unfortunately, when you are using three or more touches at a time, the screen has a tendency to lose track of one or more of those fingers. It’s hard to programmatically track smooth gestures when you go beyond two finger touches. Touches are not grouped. If, for example, you touch the screen with two fingers from each hand, there’s no way to determine which touches belong to which hand.The touch order is arbitrary. Although grouped touches retain the same finger order for the lifetime of a single touch event (down, move, up), the order may change the next time your user touches the screen.When you need to distinguish touches from each other, build a touch dictionary indexed by the touch objects. Note The drawRect: routine in Recipe 2-4 clears its context each time it is called. This removes previous circles and lines from the display. Comment out this line if you want to see an event trail.
Slide 80: Recipe: Detecting Multitouch 57 Figure 2-6 The iPhone enables you to capture multitouch events as well as single-touch ones. In this example, two circles mark the points at which the user has touched the screen. Recipe 2-4 Visualizing Multitouch @interface MultiTouchView : UIView { CGPoint loc1, loc2; } @property (nonatomic) CGPoint loc1; @property (nonatomic) CGPoint loc2; @end @implementation MultiTouchView @synthesize loc1; @synthesize loc2; - (BOOL) isMultipleTouchEnabled {return YES;} - (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event { NSArray *allTouches = [touches allObjects]; int count = [allTouches count]; if (count > 0) loc1 = [[allTouches objectAtIndex:0] locationInView:self]; if (count > 1) loc2 = [[allTouches objectAtIndex:1] locationInView:self];
Slide 81: 58 Chapter 2 Views Recipe 2-4 } Continued [self setNeedsDisplay]; // React to moved touches the same as to "began" - (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event { [self touchesBegan:touches withEvent:event]; } - (void) drawRect: (CGRect) aRect { // Get the current context CGContextRef context = UIGraphicsGetCurrentContext(); CGContextClearRect(context, aRect); // Set up the stroke and fill characteristics CGContextSetLineWidth(context, 3.0f); CGFloat gray[4] = {0.5f, 0.5f, 0.5f, 1.0f}; CGContextSetStrokeColor(context, gray); CGFloat red[4] = {0.75f, 0.25f, 0.25f, 1.0f}; CGContextSetFillColor(context, red); // Draw a line between the two location points CGContextMoveToPoint(context, loc1.x, loc1.y); CGContextAddLineToPoint(context, loc2.x, loc2.y); CGContextStrokePath(context); CGRect p1box = CGRectMake(loc1.x, loc1.y, 0.0f, 0.0f); CGRect p2box = CGRectMake(loc2.x, loc2.y, 0.0f, 0.0f); float offset = -8.0f; // circle point 1 CGMutablePathRef path = CGPathCreateMutable(); CGPathAddEllipseInRect(path, NULL, CGRectInset(p1box, offset, offset)); CGContextAddPath(context, path); CGContextFillPath(context); CFRelease(path); // circle point 2 path = CGPathCreateMutable(); CGPathAddEllipseInRect(path, NULL, CGRectInset(p2box, offset, offset)); CGContextAddPath(context, path); CGContextFillPath(context); CFRelease(path); } @end
Slide 82: UIView Animations 59 Note Apple provides many Core Graphics/Quartz 2D resources on its developer Web site. Although these forums, mailing lists, and source code samples are not iPhone specific, they offer an invaluable resource for expanding your iPhone Core Graphics knowledge. UIView Animations UIView animation provides one of the odd but lovely perks of working with the iPhone as a development platform. It enables you to slow down changes when updating views, producing smooth animated results that enhance the user experience. Best of all, this all occurs without you having to do much work. UIView animations are perfect for building a visual bridge between a view’s current and changed states.With them, you emphasize visual change and create an animation that links those changes together. Animatable changes include the following: Changes in location—moving a view around the screen Changes in size—updating the view’s frame Changes in transparency—altering the view’s alpha value Changes in rotation or any other affine transforms that you apply to a view n n n n Building UIView Animation Blocks UIView animations work as blocks, a complete transaction that progresses at once. Start the block by issuing beginAnimations:context:. End the block with commitAnimations.These class methods are sent to UIView and not to individual views. In the block between these two calls, you define the way the animation works and perform the actual view updates.The animation controls you’ll use are as follows: beginAnimations:context. Marks the start of the animation block. setAnimationCurve. Defines the way the animation accelerates and decelerates. Use ease-in/ease-out (UIViewAnimationCurveEaseInOut) unless you have some compelling reason to select another curve.The other curve types are ease in (accelerate into the animation), linear (no animation acceleration), and ease out (accelerate out of the animation). Ease-in/ease-out provides the most naturalfeeling animation style. setAnimationDuration. Specifies the length of the animation, in seconds.This is really the cool bit.You can stretch out the animation for as long as you need it to run. Be aware of straining your user’s patience and keep your animations below a second or two in length. commitAnimations. Marks the end of the animation block. n n n n
Slide 83: 60 Chapter 2 Views Sandwich your actual view change commands after setting up the animation details and before ending the animation. Listing 2-8 shows UIView animations in action by setting an animation curve and the animation duration (here, one second).The actual change being animated is a transparency update.The alpha value of the content view goes to zero, making it invisible. Instead of the view simply disappearing, this animation block slows down the change and fades it out of sight. Note Apple often uses two animation blocks one after another to add bounce to their animations. For example, they might zoom into a view a bit more than needed and then use a second animation to bring that enlarged view down to its final size. Use “bounces” to add a little more life to your animation blocks. Be sure that the animations do not overlap. Either add a delay so that the second animation does not start until the first ends (performSelector: withObject: afterDelay:) or assign an animation delegate callback (animationDidStop: finished:) to catch the end of the first animation and start the second. Listing 2-8 Using UIView Animation Calls [UIView beginAnimations:nil context:context]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationDuration:1.0]; [contentView setAlpha:0.0f]; [UIView commitAnimations]; Recipe: Fading a View In and Out There are times you’ll want to add information to your screen that overlays your view but does not of itself do anything. For example, you might show a top scores list or some instructions or provide a context-sensitive tool tip. Recipe 2-5 demonstrates how to use a UIView animation block to slowly fade a noninteractive overlay view into and out of sight. This is done by creating a custom ToggleView. As defined by this code, ToggleViews are UIViews with one child, an image view.When tapped, the animation block toggles the alpha setting from off to on or on to off.The key bits for making this happen well and reliably are as follows: Make sure the child does not look for interaction events. Cocoa Touch does not allow transparent views to catch touches. So you must allow the parent, the ToggleView, to handle all user interactions instead.When creating the child, the method sets the child’s property userInteractionEnabled to NO. n
Slide 84: Recipe: Fading a View In and Out 61 n n Make sure to catch only mouse down events. For simple on-off-on-off toggles, catch and respond only to presses for the most natural user feedback. Otherwise, user taps will hide and then immediately show your image view again. Pick a reasonable animation time. If you lengthen the animation beyond what your user is willing to handle, you’ll end up handling new taps before the first animation has completed.The one-second animation shown here is just about the longest time you’ll want to use. Half- or quarter-second animations are better for common interface changes. Using UIView Animations with Transparency Changes Recipe 2-5 @interface ToggleView: UIView { BOOL isVisible; UIImageView *imgView; } @end @implementation ToggleView - (id) initWithFrame: (CGRect) aFrame; { self = [super initWithFrame:aFrame]; isVisible = YES; imgView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] ➥applicationFrame]]; [imgView setImage:[UIImage imageNamed:@"alphablend.png"]]; imgView.userInteractionEnabled = NO; [self addSubview:imgView]; [imgView release]; return self; } - (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event { // only respond to mouse down events UITouch *touch = [touches anyObject]; if ([touch phase] != UITouchPhaseBegan) return; isVisible = !isVisible; CGContextRef context = UIGraphicsGetCurrentContext(); [UIView beginAnimations:nil context:context]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationDuration:1.0]; [imgView setAlpha:(float)isVisible];
Slide 85: 62 Chapter 2 Views Recipe 2-5 Continued [UIView commitAnimations]; } - (void) dealloc { [imgView release]; [super dealloc]; } @end Recipe: Swapping Views The UIView animation block doesn’t limit you to a single change. Recipe 2-6 combines frame size updates with transparency changes to create a more compelling animation. You do this by adding several directives at once to the animation block. Recipe 2-6 performs four actions at a time. It zooms and fades one view into place, while zooming out and fading away another. Figure 2-7 provides a preview of this animation in action. Figure 2-7 Issuing several view changes within a single UIView animation block can create complex visual effects.
Slide 86: Recipe: Swapping Views 63 Recipe 2-6 Combining Multiple View Changes in Animation Blocks @interface ToggleView: UIView { BOOL isOne; UIImageView *imgView1, *imgView2; } @end @implementation ToggleView #define BIGRECT CGRectMake(0.0f, 0.0f, 320.0f, 435.0f) #define SMALLRECT CGRectMake(130.0f, 187.0f, 60.0f, 60.0f) - (id) initWithFrame: (CGRect) aFrame; { self = [super initWithFrame:aFrame]; // Load both views, make them noninteractive imgView1 = [[UIImageView alloc] initWithFrame:BIGRECT]; imgView2 = [[UIImageView alloc] initWithFrame:SMALLRECT]; [imgView1 setImage:[UIImage imageNamed:@"one.png"]]; [imgView2 setImage:[UIImage imageNamed:@"two.png"]]; imgView1.userInteractionEnabled = NO; imgView2.userInteractionEnabled = NO; // image 1 is in front of image 2 to begin [self addSubview:imgView2]; [self addSubview:imgView1]; isOne = YES; [imgView1 release]; [imgView2 release]; return self; } - (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event { // Determine which view occupies which role UIImageView *big = isOne ? imgView1 : imgView2; UIImageView *little = isOne ? imgView2 : imgView1; isOne = !isOne; // Pack all the changes into the animation block CGContextRef context = UIGraphicsGetCurrentContext(); [UIView beginAnimations:nil context:context]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationDuration:1.0]; [big setFrame:SMALLRECT];
Slide 87: 64 Chapter 2 Views Recipe 2-6 Continued [big setAlpha:0.5]; [little setFrame:BIGRECT]; [little setAlpha:1.0]; [UIView commitAnimations]; // Hide the shrunken "big" image. [big setAlpha:0.0f]; [[big superview] bringSubviewToFront:big]; } -(void) dealloc { [imgView1 release]; [imgView2 release]; [super dealloc]; } @end Recipe: Flipping Views Transitions enable you to extend your UIView animation blocks to add even more visual flair.Two transitions—UIViewAnimationTransitionFlipFromLeft and UIViewAnimationTransitionFlipFromRight—enable you to do just what their names suggest. At this time, you can flip views left or flip views right.These are the only two official transitions available for UIViews. Note During the SDK beta period, Apple promised additional animations that were never realized, specifically UIViewAnimationTransitionCurlUp and UIViewAnimationTransitionCurlDown. These extra animations may appear at some future time. To use transitions in UIView animation blocks, you need to do two things. First, you must add the transition as a block parameter. Use setAnimationTransition: to assign the transition to the enclosing UIView animation block. Second, you should rearrange the view order while inside the block.This is best done with exchangeSubviewAtIndex: withSubviewAtIndex:. Recipe 2-7 demonstrates how to create a simple flip view using these techniques.When tapped, the views use the animation to flip from one side to the next, as shown in Figure 2-8. Do not confuse the UIView animation blocks with the Core Animation CATransition class. Unfortunately, you cannot assign a CATransition to your UIView animation.To use a CATransition, you must apply it to a UIView’s layer, which is shown in the next recipe.
Slide 88: Recipe: Flipping Views 65 Figure 2-8 Use UIView’s built-in transition animations to flip your way from one view to the next. Recipe 2-7 Using Transitions with UIView Animation Blocks @interface FlipView : UIImageView @end @implementation FlipView - (void) touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event { // Start Animation Block CGContextRef context = UIGraphicsGetCurrentContext(); [UIView beginAnimations:nil context:context]; [UIView setAnimationTransition: UIViewAnimationTransitionFlipFromLeft ➥forView:[self superview] cache:YES]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationDuration:1.0]; // Animations [[self superview] exchangeSubviewAtIndex:0 withSubviewAtIndex:1]; // Commit Animation Block [UIView commitAnimations]; } @end
Slide 89: 66 Chapter 2 Views Recipe: Applying CATransitions to Layers Core Animation Transitions expand your UIView animation vocabulary with just a few small differences in implementation. CATransitions work on layers rather than on views. Layers are the Core Animation rendering surfaces associated with each UIView. When working with Core Animation, you apply CATransitions to a view’s default layer ([myView layer]) rather than the view itself. You don’t set your parameters through UIView the way you do with UIView animation. You create a Core Animation object, set its parameters, and then add the parameterized transition to the layer. Listing 2-9 shows a simple pushFromLeft method that you might swap out for the flip method shown in Recipe 2-7. Animations use both a type and a subtype. The type specifies the kind of transition used.The subtype sets its direction.Together the type and subtype tell how the views should act when you apply the animation to them. Core Animation Transitions are distinct from the two UIView flips discussed in the previous recipe. Cocoa Touch offers four types of Core Animation.These available types include cross fades, pushes (used in Listing 2-9), reveals (where one view slides off anoth er), and covers (where one view slides onto another).The last three types enable you to specify the direction of motion for the transition through subtypes. For obvious reasons, cross fades do not have a direction and they do not use subtypes. Core Animation is part of the Quartz Core framework.To use this sample code, you must add the Quartz Core framework to your project and import <QuartzCore/ QuartzCore.h> into your code. Note Apple’s Core Animation features 2D and 3D routines built around Objective-C classes. These classes provide graphics rendering and animation for your iPhone and Macintosh applications. Core Animation avoids many low-level development details associated with, for example, direct OpenGL while retaining the simplicity of working with hierarchical views. Listing 2-9 Adding a Core Animation Transition to a UIView Layer @implementation PushView - (void) touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event { CATransition *animation = [CATransition animation]; [animation setDelegate:self]; [animation setDuration:1.0f]; [animation setTimingFunction:UIViewAnimationCurveEaseInOut]; [animation setType: kCATransitionPush]; [animation setSubtype: kCATransitionFromLeft]; [[self superview] exchangeSubviewAtIndex:0 withSubviewAtIndex:1];
Slide 90: Recipe: Applying CATransitions to Layers 67 Listing 2-9 Continued [[[self superview] layer] addAnimation:animation ➥forKey:@"transitionViewAnimation"]; } @end Undocumented Animation Types The iPhone actually implements more animation types than official documents would suggest. As Listing 2-10 shows, the iPhone is perfectly capable of handling map curls à la the Google Maps application.This code, which works on the iPhone but not the Simulator, relies on extracting animation names from the UIKit binary framework file. Like all undocumented calls, this is not without risk. Apple may change or delete these animations at any time. Other animation types include pageCurl, pageUnCurl, suckEffect, spewEffect, cameraIris (from the Photos application), cameraIrisHollowOpen, cameraIrisHollowClose, genieEffect (typically used for deleting garbage), unGenieEffect, rippleEffect, twist, tubey, swirl, charminUltra, zoomyIn, zoomyOut, and oglFlip. Note the use of setRemovedOnCompletion: NO.This freezes the animation at its end, allowing the curled map to remain visible, as shown in Figure 2-9. Figure 2-9 This eye-catching effect uses an undocumented Core Animation type called mapCurl.
Slide 91: 68 Chapter 2 Views Listing 2-10 Calling Undocumented Animation Types - (void) performCurl { // Curl the image up or down CATransition *animation = [CATransition animation]; [animation setDelegate:self]; [animation setDuration:1.0f]; [animation setTimingFunction:UIViewAnimationCurveEaseInOut]; [animation setType:(notCurled ? @"mapCurl" : @"mapUnCurl")]; [animation setRemovedOnCompletion:NO]; [animation setFillMode: @"extended"]; [animation setRemovedOnCompletion: NO]; notCurled = !notCurled; [[topView layer] addAnimation:animation forKey:@"pageFlipAnimation"]; } General Core Animation Calls The iPhone provides partial support for Core Animation calls. By partial, I mean that many standard classes are missing in action. CIFilter is one such class. It’s not included in Cocoa Touch, although the CALayer and CATransition classes are both filter-aware. If you’re willing to work through these limits, you can freely use standard Core Animation calls in your programs. Listing 2-11 shows iPhone native Core Animation code based on a sample from Lucas Newman (http://lucasnewman.com).When run, this method scales down and fades away the contents of a UIImageView.The source adds a translucent reflection layer, which follows the view. This code remains virtually unchanged from the Mac OS X sample it was based on. More complex Core Animation samples may offer porting challenges, but for simple reflections, shadows, and transforms, all the functionality you need can be had at the native iPhone level. Listing 2-11 Native iPhone Core Animation Calls // Adapted from http://lucasnewman.com/animationsamples.zip - (void) scaleAndFade { // create the reflection layer CALayer *reflectionLayer = [CALayer layer]; // share the contents image with the screen layer reflectionLayer.contents = [contentView layer].contents; reflectionLayer.opacity = 0.4; reflectionLayer.frame = CGRectOffset([contentView layer].frame, 0.5, ➥416.0f + 0.5);
Slide 92: Recipe: Swiping Views 69 Listing 2-11 Continued // flip the y-axis reflectionLayer.transform = CATransform3DMakeScale(1.0, -1.0, 1.0); reflectionLayer.sublayerTransform = reflectionLayer.transform; [[contentView layer] addSublayer:reflectionLayer]; #define ANIMATION_DURATION (4.0) [CATransaction begin]; [CATransaction setValue:[NSNumber numberWithFloat:ANIMATION_DURATION] ➥forKey:kCATransactionAnimationDuration]; // scale it down CABasicAnimation *shrinkAnimation = [CABasicAnimation ➥animationWithKeyPath:@"transform.scale"]; shrinkAnimation.timingFunction = [CAMediaTimingFunction ➥functionWithName:kCAMediaTimingFunctionEaseIn]; shrinkAnimation.toValue = [NSNumber numberWithFloat:0.0]; [[contentView layer] addAnimation:shrinkAnimation forKey:@"shrinkAnimation"]; // fade it out CABasicAnimation *fadeAnimation = [CABasicAnimation ➥animationWithKeyPath:@"opacity"]; fadeAnimation.toValue = [NSNumber numberWithFloat:0.0]; fadeAnimation.timingFunction = [CAMediaTimingFunction functionWithName: ➥kCAMediaTimingFunctionEaseIn]; [[contentView layer] addAnimation:fadeAnimation forKey:@"fadeAnimation"]; [CATransaction commit]; } Recipe: Swiping Views Swipes are a convenient but often-overlooked iPhone interaction style.When a user quickly drags his or her finger across the screen, the UITouch objects returned for that gesture include an info property.This property defines the direction in which the user swiped the screen, (for example, up, down, left, or right).This behavior is best seen in the iPhone’s Photos application, when users swipe left or right to move between album pictures. Early versions of the iPhone SDK offered swipe detection as a standard part of the UITouch object, but later releases dropped that capability. Instead, Apple offered workaround code in its iPhone Developers Guide. Recipe 2-8 is based on that code. It ensures that a user continues finger movement in one direction by defining a safety zone around the movement. If the user strays diagonally more than 6 pixels off course, the swipe cancels. Stay on-course for at least 12 pixels and the swipe is set.
Slide 93: 70 Chapter 2 Views Recipe 2-8 applies a Core Animation Transition on completion of a successful swipe. It uses the swipe direction to set the animation’s subtype. Subtypes are used in Core Animation to specify the overall movement of the animation, whether up, down, or sideways. This sample mimics the interaction style used for browsing through album pictures in Photos but allows you to move up and down as well as left and right. If you comment out the kCATransitionPush animation type and replace it with the undocumented oglFlip in the line that immediately follows it, you’ll receive an even nicer surprise. Far from being limited to the two core flip directions, the iPhone actually supports a full four-way flip style, albeit one that Apple has not included in its public SDK. Note In early releases of the iPhone SDK, swipes didn’t work in the Simulator. In later versions, they did. Should you encounter platform limitations while developing (for example, when working with the Camera), you can easily add workarounds based on testing the platform. Add compiler directives such as #if defined(TARGET_IPHONE_SIMULATOR) to your source. Recipe 2-8 Detecting and Responding to User Swipes in Your Views - (CATransition *) getAnimation:(NSString *) direction { CATransition *animation = [CATransition animation]; [animation setDelegate:self]; [animation setType:kCATransitionPush]; // [animation setType:@"oglFlip"]; [animation setSubtype:direction]; [animation setDuration:1.0f]; [animation setTimingFunction:[CAMediaTimingFunction ➥functionWithName:kCAMediaTimingFunctionEaseInEaseOut]]; return animation; } #define HORIZ_SWIPE_DRAG_MIN 12 #define VERT_SWIPE_DRAG_MAX 4 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; startTouchPosition = [touch locationInView:self]; dirString = NULL; } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
Slide 94: Recipe: Swiping Views 71 Recipe 2-8 Continued UITouch *touch = touches.anyObject; CGPoint currentTouchPosition = [touch locationInView:self]; if (fabsf(startTouchPosition.x - currentTouchPosition.x) >= HORIZ_SWIPE_DRAG_MIN && fabsf(startTouchPosition.y - currentTouchPosition.y) <= VERT_SWIPE_DRAG_MAX) { // Horizontal Swipe if (startTouchPosition.x < currentTouchPosition.x) { dirString = kCATransitionFromLeft; } else dirString = kCATransitionFromRight; } else if (fabsf(startTouchPosition.y - currentTouchPosition.y) >= HORIZ_SWIPE_DRAG_MIN && fabsf(startTouchPosition.x - currentTouchPosition.x) <= VERT_SWIPE_DRAG_MAX) { // Vertical Swipe if (startTouchPosition.y < currentTouchPosition.y) dirString = kCATransitionFromBottom; else dirString = kCATransitionFromTop; } else { // Process a non-swipe event. // dirString = NULL; } } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { if (dirString) { CATransition *animation = [self getAnimation:dirString]; [[self superview] exchangeSubviewAtIndex:0 withSubviewAtIndex:1]; [[[self superview] layer] addAnimation:animation forKey:kAnimationKey]; } }
Slide 95: 72 Chapter 2 Views Recipe: Transforming Views Affine transforms enable you to change an object’s geometry by mapping that object from one view coordinate system into another.The iPhone SDK fully supports standard affine 2D transforms.With them, you can scale, translate, rotate, and skew your views however your heart desires and your application demands. Transforms are defined in Core Graphics, and consist of calls such as CGAffineTransformMakeRotation and CGAffineTransformScale.These build and modify the 3-by-3 transform matrices. Once built, use UIView‘s setTransform: call to apply 2D affine transformations to UIView objects. Recipe 2-9 demonstrates how to build and apply an affine transform of a UIView.To create the sample, I kept things simple. I build an NSTimer that ticks every 1/30th of a second. On ticking, it rotates a view by 1% of pi and scales over a cosine curve. I use the cosine’s absolute value for two reasons. It keeps the view visible at all times, and it provides a nice bounce effect when the scaling changes direction.This produces a rotating and undamped bounce animation. This is one of those samples that it’s best to build and view as you read through the code.You’ll be better able to see how the handleTimer: method correlates to the visual effects you’re looking at. Recipe 2-9 Example of an Affine Transform of a UIView #import "math.h" #define PI 3.14159265 @interface HelloController : UIViewController { UIView *contentView; UIImageView *rotateView; int theta; } @end @implementation HelloController - (id)init { if (self = [super init]) self.title = @"Affine Demo"; return self; } - (void) handleTimer: (NSTimer *) timer { // Rotate each iteration by 1% of PI float angle = theta * (PI / 100); CGAffineTransform transform = CGAffineTransformMakeRotation(angle); theta = (theta + 1) % 200;
Slide 96: Recipe: Transforming Views 73 Recipe 2-9 Continued // For fun, scale by the absolute value of the cosine float degree = cos(angle); if (degree < 0.0) degree *= -1.0f; degree += 0.5f; CGAffineTransform scaled = CGAffineTransformScale(transform, degree, degree); // Apply the affine transform [rotateView setTransform:scaled]; } - (void)loadView { theta = 0; contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] ➥applicationFrame]]; rotateView = [[UIImageView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 240.0f, ➥240.0f)]; [rotateView setImage:[UIImage imageNamed:@"rotateart.png"]]; [rotateView setCenter:CGPointMake(160.0f, 208.0f)]; [contentView addSubview:rotateView]; [rotateView release]; self.view = contentView; [contentView release]; [NSTimer scheduledTimerWithTimeInterval: 0.03f target: self selector: ➥@selector(handleTimer:) userInfo: nil repeats: YES]; } // Allow the view to respond to iPhone Orientation changes (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation) interfaceOrientation { return NO; } -(void) dealloc { [contentView release]; [rotateView release]; [super dealloc]; } @end
Slide 97: 74 Chapter 2 Views Centering Landscape Views Use the same affine transform approach to center landscape-oriented views. Listing 2-12 creates a 480-by-320 pixel view, centers it at [160, 240] (using portrait view coordinates), and then rotates it into place. Half of pi corresponds to 90 degrees, creating a landscaperight rotation. Centering keeps the entire view onscreen. All subviews, including text fields, labels, switches, and so on rotate into place along with the parent view. If you want to work with a landscape keyboard for this view, make sure to call [[UIApplication sharedApplication] setStatusBarOrientation: UIInterfaceOrientationLandscapeRight].This sets the status bar orientation, which controls the keyboard regardless of whether the status bar is hidden or shown. Listing 2-12 Rotating Landscape Views into Place @implementation HelloController - (void)loadView { contentView = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 480.0f, ➥320.0f)]; [contentView setCenter:CGPointMake(160.0f, 240.0f)]; [contentView setBackgroundColor:[UIColor blackColor]]; [contentView setTransform:CGAffineTransformMakeRotation(3.141592f / 2.0f)]; self.view = contentView; [contentView release]; } -(void) dealloc { [contentView release]; [super dealloc]; } @end Summary UIViews provide the onscreen components your users see and interact with. As this chapter has shown, even in their most basic form, they offer incredible flexibility and power.You’ve discovered how to use views to build up elements on a screen, create multiple interaction objects, and introduce eye-catching animation. Here’s a collection of thoughts about the recipes you’ve seen in this chapter that you might want to ponder before moving on: n When dealing with multiple onscreen views, hierarchy should always remain frontmost in your mind—no pun! Use your view hierarchy vocabulary (bringSubviewToFront:, sendSubviewToBack:,
Slide 98: Summary 75 n n n n n exchangeSubviewAtIndex:withSubviewAtIndex:) to take charge of your views and always present the proper visual context to your users. You’re not limited to rectangles. Use UIView / Core Graphics clipping to create compelling interaction objects that don’t necessarily have right corners. Be concrete.The iPhone has a perfectly good touch screen.Why not let your users drag items around the screen with their fingers? It adds to the reality and the platform’s interactive nature. Animate everything. Animations don’t have to be loud, splashy, or bad design.The iPhone’s strong animation support enables you to add smooth transitions between user tasks. Short, smooth, focused changes are the iPhone’s bread and butter. Users typically have five fingers per hand. Don’t limit yourself to a one-finger interface when it makes sense to expand your interaction into multitouch territory. A solid grounding in Quartz graphics and Core Animation will be your friend. Using drawRect:, you can build any kind of custom UIView presentation you’d like, including text, Bézier curves, scribbles, and so forth. n Explore! This chapter has only touched lightly on the ways you can use UIViews in your applications. Use this material as a jumping-off point to explore the full vocabulary of the UIView class.
Slide 100: 3 View Controllers The iPhone screen isn’t big by any programsIt’s just a fewa inchesphysicalbyviewport. measure. across a few inches high.This diminutive size constrains by limiting user’s Although your virtual worlds may be very large indeed, the small physical screen means that iPhone classes must cleverly expand their practical interaction space. In this chapter, you’re about to discover numerous ways to create virtual presentations that enlarge your application’s physical reality through the use of view controllers.You’ll discover how to use view controllers to build navigable worlds and how to connect to these classes using Interface Builder. View Management On the iPhone, view controllers centralize basic view management.They provide practical utility by linking the view functionality covered in Chapter 2, “Views,” with the pragmatic reality of your device.View controllers handle reorientation events such as when users tip the iPhone on its side to landscape mode and navigation issues such as when users need to move their attention from view to view.The following sections introduce the kinds of view controllers used in the iPhone SDK.You see what classes are used in the view controller paradigm, including both core classes and specialized ones. Core Classes The iPhone SDK offers any number of view controllers and their subclasses.These range from the general to the specific. Just three of these represent core controller classes.They are as follows: UIViewController. This is the parent class for view controllers and the one you use to specifically link to a single view. It’s the workhorse of view controllers and the kind you’ll spend most of your time customizing. Most important, UIViewController handles all view reorientation tasks, enabling you to easily program for both landscape and portrait orientation. n
Slide 101: 78 Chapter 3 View Controllers n UINavigationController. Use navigation controllers for navigating up and n down through tree-based view hierarchies (for example, drilling). As their name suggests, they create the blue- or gray-colored navigation bars that appear at the top of a standard iPhone application.They enable you to add buttons through the use of Navigation Items and automatically generate “back” buttons showing the title of the calling view controller. All navigation controllers use a “root” view controller to establish the top of their navigation tree. UITabBarController. Parallel views are like stations on a radio. A tab bar enables users to select which UIViewController to “tune in to,” without there being a specific navigation hierarchy.You see this best in applications like YouTube and iPod, where users select whether to see a “Top 25” list or view albums or playlists.When TabBar instances offer more than five view controller choices at a time, users can customize them through the More > Edit screen.The More > Edit screen lets users drag their favorite controllers down to the button bar at the bottom of the screen. Specialized Classes In addition to the three general classes you just read about, Apple offers many highly adapted controllers.These specialized items leverage access to the iPhone’s core databases and functions.While you can throw instances of these classes into your applications and use them like any other UIViewController, they’re preloaded with advanced functionality. Here are a few examples of the kinds of specialized view controllers available in the SDK: UIImagePickerController. This utility controller enables users to select images from onboard albums or to snap a photo from the iPhone camera. Apple has added an advanced image-selection interface.The controller even lets the users orient and zoom an image before finishing. ABNewPersonViewController. This controller enables users to create a new contact for their Address Book. Other Address Book controller styles include ABPersonViewController, ABUnknownPersonViewontroller, and n n ABPeoplePickerNavigationController. n UITableViewController. Table view controllers simplify using tables in your n iPhone projects.This controller class provides a standard already-connected UITableView instance and automatically sets delegation and data sources to point to itself. All you have to do is supply those delegate and data source methods to fill up the table with data and react to user taps. UITableViewController is discussed at length in Chapter 5, “Basic Tables.” MPMoviePlayerController. When your user needs to watch a movie or listen to audio, this controller does the trick. Just supply it with a path to the media
Slide 102: View Management 79 resource and drill down to its display.The controller provides a Done button for the user or automatically returns a delegate call when playback finishes. In a way, these specialized controllers are both a blessing and a curse. On the positive side, they introduce enormous functionality, essentially with no additional programming burden. On the downside, they’re so specialized that they often hide core features that developers might prefer to work with. For example, there’s no simple audio playing classes.You either work at the lowest level through AudioQueue, dealing with sample rates and encoding styles, or at the highest through MPMoviePlayerController.You have no access to a general scrubber bar or pause/play button.These are actually features that are hidden within the Media Player framework, but they have no publicly defined methods or classes.There used to be a public framework called Celestial that provided a QuickTime-like interface to audiovisual controllers and handy playback features, but Apple moved this framework to its Private Frameworks hierarchy for firmware versions after 1.1.4. Creating a UIViewController UIViewController instances provide tons of great core view management.What they don’t supply is an actual view. It’s up to you to create one and install it into the view controller via the loadView method. Every UIViewController and subclass implements this method, which is where you connect the controller to a view instance.You need to do two things: Initialize the view and then connect it to the controller: Initialize and size your content view by calling initWithFrame: using [[UIScreen mainScreen] applicationFrame] as its argument.This returns the standard bounds for the application.The math automatically takes any onscreen navigation bars and tab bars into account.The Hello World example in Chapter 1, “Introducing the iPhone SDK,” provided a simple example of this layout in action. Connect the view to the controller by assigning self.view to a UIView instance of some kind. Do this in your loadView method (for example, self.view = n n contentView). When working with specialized controllers, always make sure to call the superclass’s version of the method from the child (that is, [super loadView]).This ensures that children inherit the parent’s layout behavior as well as the class methods and variables. Other key UIViewController methods include the following. init Use the class init method to set the view controller’s title and other features that need to be set up before the class is actually used.To match the title to the application name, assign self.title to [[[NSBundle mainBundle] infoDictionary] objectForKey:@“CFBundleName”].This returns the name defined in the bundle’s Info.plist file.
Slide 103: 80 Chapter 3 View Controllers Unlike UIView, the UIViewController instance is an abstract object and has no physical onscreen presence. Do not set a frame the way you would with a normal UIView. UIViews use initWithFrame: and UIViewControllers use init. Set up any view frames in the well-named loadView method. shouldAutorotateToInterfaceOrientation: This method returns either YES or NO, depending on whether you want to support autorotation in your program.When returning YES, the view controller uses several flags to determine how the autorotation takes place. Listing 3-1 shows a typical code snippet from a loadView method that specifies that subviews should automatically resize both horizontally and vertically. Listing 3-1 Setting Up Autorotation Flags contentView.autoresizesSubviews = YES; contentView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight); viewDidAppear: and viewDidDisappear: These methods are called each time a UIViewController’s view is brought onscreen or pushed offscreen—typically due to navigation between views. Use these methods to refresh the view to reflect the current data state and update stored data.These methods enable you to claim or resign first-responder status for text elements, remove text selections if needed, or perform any other bookkeeping that needs to be done before returning control to the user. didRotateFromInterfaceOrientation: Programmatically catch orientation changes by implementing this method in your UIViewController subclass.This method enables you to respond to the new orientation and passes the previous orientation in case you want to perform a specific animation type based on the change involved. It is entirely possible to move from one orientation to another without passing through the intermediate phases you’d expect, so avoid assumptions. Use the actual data passed to this method. Note Apple has promised support for separate landscape and portrait views in the SDK at some point. At the time of writing, this functionality has not yet been implemented. It’s up to you to rearrange your screen when the orientation changes. To force your application into landscape mode, return NO for shouldAutorotateToInterfaceOrientation:, call [[UIApplication sharedApplication] setStatusBarOrientation: UIInterfaceOrientationLandscapeRight] from your applicationDidFinishLaunching: method, and set UIInterfaceOrientation to UIInterfaceOrientationLandscapeRight in your Info.plist file.
Slide 104: Working with Interface Builder to Build Views for UIViewControllers 81 Working with Interface Builder to Build Views for UIViewControllers Interface Builder, with its interactive GUI layout tools, helps create UIView content. It makes it possible for you to add interactive controls, moving them around the screen by hand to design one-of-a-kind interfaces. Interface Builder excels at UIView layout. It offers little or no direct support for UIViewController behavior.That’s because the UIViewController is an abstract class, and UIView is a concrete one. While taking that limitation into account, you can use Interface Builder to embed your UIView material into UIViewController instances and into other view controller classes.The workflow you’re about to read through lets you combine the power of Interface Builder’s design tools with the convenience of view controller classes. Temperature Conversion Example This example creates a classic Fahrenheit to Celsius conversion using a combination of Xcode and Interface Builder. A UIView subclass defines the conversion behavior. This view connects the buttons and text fields and gives them meaning by adding a convert: function to perform the math. The view is embedded into a trivial UIViewController subclass.This controller typically takes over any autorotation and view navigation tasks. In this example, it doesn’t actually do much other than demonstrate how views are created and added to controllers using the Interface Builder tool. In the following steps, you create a new Xcode project, populate it with the convert source code, and then lay out the GUI using Interface Builder’s tools: 1. Create a new Xcode project. In Xcode, choose File, New Project. Create a new Cocoa Touch Application ViewBased project and name it however desired. Keep the name short. Both Xcode and Interface Builder use that project name to define your application delegate, so a simple name works best. 2. Clean up the project and replace the code. Select the Classes subfolder and delete it.This leaves main.m as your sole remaining source file. Open it and replace its contents with Listing 3-2. Change the name of the application delegate (here WalkThroughAppDelegate) to match your project name. Notice the two IBOutlet text fields and the IBAction return type.The IBOutlet keyword indicates objects to be defined in Interface Builder. IBAction tells Interface Builder to treat methods as the action for target/action pairs. IBAction is functionally equivalent to (void). Listing 3-2 Converter Source #import <UIKit/UIKit.h> // Custom view that converts temperatures
Slide 105: 82 Chapter 3 View Controllers Listing 3-2 Continued @interface MyView : UIView { IBOutlet UITextField *infield; IBOutlet UITextField *outfield; } @end @implementation MyView - (IBAction) convert: (id) sender { float invalue = [[infield text] floatValue]; float outvalue = (invalue - 32.0f) * 5.0f / 9.0f; [outfield setText:[NSString stringWithFormat:@"%3.2f", outvalue]]; } @end // View controller that autorotates @interface MyViewController : UIViewController @end @implementation MyViewController -(void) loadView { [super loadView]; self.view.autoresizesSubviews = YES; self.view.autoresizingMask = (UIViewAutoresizingFlexibleWidth | ➥UIViewAutoresizingFlexibleHeight); } - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation) interfaceOrientation { return YES; } @end // Application delegate that uses NIB objects @interface WalkThroughAppDelegate : NSObject { IBOutlet UIWindow *window; IBOutlet MyView *contentView; } @end @implementation WalkThroughAppDelegate - (void)applicationDidFinishLaunching:(UIApplication *)application { [window addSubview:contentView]; [window makeKeyAndVisible]; }
Slide 106: Working with Interface Builder to Build Views for UIViewControllers 83 Listing 3-2 Continued - (void)dealloc { [contentView release]; [window release]; [super dealloc]; } @end int main(int argc, char *argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; int retVal = UIApplicationMain(argc, argv, nil, nil); [pool release]; return retVal; } 3. Launch Interface Builder. Double-click the MainWindow.xib file in your project (see Figure 3-1).This opens it in Interface Builder. Figure 3-1 Xcode automatically creates a MainWindow.xib file in your project. Double-click this file to launch Interface Builder.
Slide 107: 84 Chapter 3 View Controllers 4. Set up your windows. When Interface Builder launches, your MainWindow.nib project contains five objects: a file owner, an application delegate object (named with your project name), a First Responder object, a view controller, and a window (see Figure 3-2). Figure 3-2 The default Xcode XIB file contains a file owner, an application delegate, and a window. 5. Open the Inspector and Library. Select Tools, Inspector (Command-Shift-I) and Tools, Library (Command-Shift-L). These two windows provide two of the key tools for working in Interface Builder: The Library provides a set of reusable Cocoa Touch objects.You can drag these objects from the Library window into your application. n n The Inspector enables you to view and customize the interface objects in your project. Use the Inspector to see how objects are connected together and what classes they link to. 6. Set Up your application delegate. Tap the application delegate object in your main XIB window. (It’s the one that’s not the file’s owner or window).Then either tap the rightmost tab in the Inspector or press Command-4. Both of these actions open the Identity Inspector. In the Identity Inspector, locate the class name at the top of the window (see Figure 3-3).
Slide 108: Working with Interface Builder to Build Views for UIViewControllers 85 If you want to change the class name used by your application delegate, here is where you update it. The owner, delegate, and window objects mirror the classes used in standard applications.The file’s owner object defines the class that “owns” the XIB file (that is, the shared UIApplication instance).The application delegate object connects to the delegate, which is responsible for handling the applicationDidLaunch eventsapplicationDidFinishLaunching: callback and setting up the primary window and ordering it out for display. 7. Add outlets to the delegate. Add two outlets: window and contentView. Change the window class from id to UIWindow, and the view class to MyView.Typing these outlets adds a layer of control to your IB setup.When you make your connections, they’ll only connect to objects of the proper class. Adding class types isn’t required—and in a few steps you’ll see how to do this without typing—but it’s something you should be aware of as a developer. Figure 3-3 Use the Identity Inspector to add outlets or actions and update class names associated with Interface Builder objects.
Slide 109: 86 Chapter 3 View Controllers 8. Add an object to your project window. In your Library locate the UIViewController (it’s toward the top of the library) and UIView (it’s near the bottom). Drag one of each into your project window. Figure 3-4 shows the project window after adding these objects.These two items use this object.This item will be used to represent instances of the classesan instance of the MyView class you defined in the code:MyView and MyViewController. Dragging objects from the Library into your main XIB window adds instances of those classes to your project. Figure 3-4 9. Change the View Controller class. Tap the new View Controller. In the Identity Inspector (Command-4), change its class to MyViewController.The View Controller’s name in the project window updates to My View Controller. 10. Change the view class and add its outlets and action. Tap the new view. Use the Identity Inspector to change its class to MyView. The view in the project window changes its name to My View. Add one action (convert:) and two outlets (infield and outfield) to the view, as shown in Figure 3-5. Actions correspond to instance methods in your source code, and outlets correspond to instance variables. If you refer back to the code from Step 2 of these instructions, you see that the MyView class was defined with two IBOutlet instances and with a method to do the conversion. In the next steps, you see how to connect onscreen objects with these instance variables and methods. 11. Edit the view. Double-click My View in the project window to open its editor. From the Library, drag over two labels, one button and two fields, as shown in Figure 3-6.
Slide 110: Working with Interface Builder to Build Views for UIViewControllers 87 Figure 3-5 The Identity Inspector enables you to add outlets and actions to your objects. These correspond to instance variables and instance methods in your source code. Figure 3-6 Drag interface elements from the Interface Builder Library (Tools, Library) onto a view to begin laying out its GUI.
Slide 111: 88 Chapter 3 View Controllers 12. Edit the view. Arrange the elements in your view to roughly mimic the layout shown in Figure 3-7. Putting items toward the top of the screen leaves room for the keyboard at the bottom. If you like, use the built-in horizontal and vertical guides (Layout, Add Horizontal Guide and Layout, Add Vertical Guide) to simplify layout.These guides are similar to the ones you find in Photoshop.They are virtual placement helpers only.They do not appear in your final application. If you choose to use them, pay attention to the left and right numeric indicators they show while being moved.They let you know how many pixels are to their left and right. A vertical guide at 160 | 160 is directly in the middle of the screen. Figure 3-7 Place your interface elements toward the top of the screen to leave room for the keyboard, which will appear at the bottom. 13. Edit the left field traits. Select the left (input) field and use the Attributes Inspector (Command-1) to set its keyboard type to numbers and punctuation.There are additional traits here you will want to explore on your own time.
Slide 112: Working with Interface Builder to Build Views for UIViewControllers 89 14. Connect the application delegate to its window and view. While holding down the Control key, drag from the application delegate object in the project window to the Window object. Select Window from the pop-up.This assigns the Window object to the window instance variable of your application delegate. Next, Control-drag from the application delegate to the My View object. Select contentView from the pop-up. These actions set up the application delegate’s instance variables, creating associations between the IBOutlet instances declared in the code with the actual window and view laid out in Interface Builder. 15. Connect the view to its outlets. Open the My View window so that it can be seen. Control-drag between the My View object and the left text field. Select Infield from the pop-up.Then Controldrag from the view to the right text field and select Outfield. Again, you’re assigning objects to instance variables. 16. Connect the button to the view. Right-tap Control-drag from the Convert button you added to the custom view to the My View object. A customization pop-up appears. Scroll down the pop-up to find TouchUpInside. Drag from the circle to its right to the MyView instance in the XIB project window. Select, select convert: from the pop-up. This action connects a touch inside the button to the conversion action you defined in your object. Check on the connection by right-tapping the Convert button again.The pop-up confirms this connection, as shown in Figure 3-8. Figure 3-8 Once connected, you can view both the target and the action associated with a touch event. 17. Add the view to its controller. Double-tap My View Controller to open its editor. Drag the My View instance from the project window onto this editor. It automatically jumps into place. Notice the right-pointing arrow at the top right of the View Controller editor.
Slide 113: 90 Chapter 3 View Controllers This allows you to preview your view in landscape as well as in portrait mode. Go ahead and do this, and make any adjustments needed to provide a satisfactory landscape presentation. By assigning the view to a controller, you enable that view controller to assume responsibilities for that view in your application.You do not need to make any further formal connections in Interface Builder. 18. Save. Save your changes in Interface Builder and return to Xcode. 19. Run. In Xcode, set your active SDK to either the device or the Simulator and run the completed application. Figure 3-9 shows the final result with a view whose elements have been fully defined in Interface Builder connected to a simple UIViewController of your design. Figure 3-9 The completed application binds the custom-built view to the UIViewController you specified. Loading XIB Files Directly Cocoa Touch lets you recover objects from any XIB file by calling loadNibNamed: owner: options:.This returns an array of objects initialized from the NIB/XIB bundle, which you can then grab and use in your program.
Slide 114: Navigation Controllers 91 NSArray *niblets = [[NSBundle mainBundle] loadNibNamed:@”sample” owner:self options:NULL]; for (id theObject in niblets) { if ([theObject isKindOfClass:[UIViewController class]]) [self.navigationController pushViewController:theObject ➥animated:YES]; } Navigation Controllers The UINavigationController class provides all the high-calorie goodness of a UINavigationBar-based interface with little programming. Navigation controllers enable you to smoothly move between views using built-in animation.You also get history control.The controller handles all the Back button functionality.This means that parent view titles automatically appear as Back buttons and you can “pop the stack,” so to speak, without any programming. And if that weren’t enough, the navigation controller also offers a simple menu bar. You can add buttons—or even more complicated controls—into the bar to build actions into your application. Between these three features of navigation, history, and menus, navigation controllers build a lot of wow into a simple-to-program package. The following recipes introduce these core navigation controller features from building menus to building a history stack. In these examples, you see how to use the UINavigationBar class to create a variety of novel and useful interfaces. Setting Up a Navigation Controller Whether you plan to use a navigation controller to simplify moving between views—its intended use—you should understand how the navigation controller works. At their simplest level, navigation controllers manage view controller stacks. Every navigation controller owns a root view controller.This controller forms the base of the stack.You can push other controllers onto the stack.This extends the navigation breadcrumb trail and automatically builds a Back button.You can pop controllers off the stack by tapping one of these Back buttons. And you can pop back until you reach the root.Then you can go no further.The root is the root, and you cannot pop below that root. This stack-based design lingers even when you plan to use just one view controller. You might want to leverage the UINavigationController’s built-in navigation bar to build a two-button menu, for example.This would disregard any navigational advantage of the stack.You still need to set that one controller as the root via initWithRootViewController:. Listing 3-3 shows the creation and initialization of a navigation controller from a typical applicationDidFinishLaunching: method.The controller is allocated, initialized with a root view, and then added to the main window via its view property.
Slide 115: 92 Chapter 3 View Controllers Listing 3-3 Initializing a Navigation Controller - (void)applicationDidFinishLaunching:(UIApplication *)application { UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] ➥bounds]]; UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController: [[HelloController alloc] init]]; [window addSubview:nav.view]; [window makeKeyAndVisible]; } Pushing and Popping View Controllers Add new items onto the navigation stack by pushing a new controller with pushViewController: animated:. Send this call to the parent navigation controller of any UIViewController (for example, [self navigationController]).When pushed, the new controller slides onscreen (assuming you set animated to YES). A leftpointing Back button appears, leading you one step back on the stack.The Back button uses the title of the previous view controller. There are many reasons you’d push a new view.Typically, these involve navigating to subviews like detail views or drilling down a file structure.You normally push controllers onto the navigation controller stack after your user taps a button, a table item, or a disclosure accessory. Perform push requests and other navigation bar customization inside your UIViewController subclasses.There’s no reason or need to subclass UINavigationController.You have direct access to the navigation bar and its features. Here is a line from a loadView method that customizes the navigation bar style using a chain of properties: self.navigationController.navigationBar.barStyle = UIBarStyleBlackTranslucent; Modal Presentation Modal presentation offers another way to present a view controller. After sending the presentModalViewController: animated: message, a new view controller slides up into the screen and takes control until it’s dismissed with dismissModalViewControllerAnimated:.This enables you to add special-purpose dialogs into your applications.Typically, modal controllers are used to pick data such as contacts from the Address Book or photos from the Library. Chapters 7, “Media,” and 9, “People, Places, and Things,” show modal view controllers in action. The Navigation Item Class The objects that populate the navigation bar are put into place using the UINavigationItem class.This class enables you to attach buttons, text, and other UI
Slide 116: Recipe: Building a Simple Two-Item Menu 93 objects into three key locations: the left, the center, and the right of the navigation bar. Typically, this works out to be a regular button on the right, some text (usually the UIViewController’s title) in the middle, and a Back-styled button on the left. But you’re not limited to that layout.You can add custom controls to any of these three locations. So you can build navigation bars with search fields, with segment controls, with toolbars, with pictures, and more. Assign these items via SetCustomLeftItem: animated:, SetCustomRightItem: animated: and by updating the customTitleView property to point to a view of your choice. Listing 3-4 shows how to add a custom button to the right navigation item view. This is a standard navigation-style UIButton (UIButtonTypeNavigation). In this example, it invokes the randomize method when pushed. Listing 3-4 Adding a Custom Button to a UINavigationItem // Add a randomize button UIBarButtonItem *randomButton = [[[UIBarButtonItem alloc] initWithTitle:@"Randomize" style:UIBarButtonItemStylePlain target:self action:@selector(randomize)] autorelease]; self.navigationItem.rightBarButtonItem = randomButton; Adding a custom view to the title space is just as simple. Instead of adding a control, assign a view.This example (from the first recipe in Chapter 5) adds a custom UILabel: self.navigationItem.titleView = [[UILabel alloc] initWithFrame:CGRectMake(0.0f, ➥4.0f, 320.0f, 36.0f)]; Recipe: Building a Simple Two-Item Menu Although many applications demand serious user interfaces, often you don’t need complexity. A simple one- or two-button menu can accomplish a lot. Use these steps to create basic interfaces for simple utilities: 1. Create a UIViewController subclass that you’ll use as your primary interaction space. 2. Allocate a navigation controller and assign an instance of your custom view controller to its root view. 3. In the custom view controller, create one or two buttons and add them to the view’s navigation item. 4. Build the callback routines that get triggered when a user taps a button. Recipe 3-1 demonstrates these steps. It creates a simple view controller called HelloController and assigns it as the root view for a UINavigationController. In the loadView method, two buttons populate the left and right custom slots for the
Slide 117: 94 Chapter 3 View Controllers view’s navigation item.When tapped, these update the background color for the main view.This recipe is not feature rich, but it provides an easy-to-build two-item menu. Figure 3-10 shows the interface in action. If you’re looking for more complexity than two items can offer, consider having the buttons trigger UIActionSheet menus. Action sheets, which are discussed in Chapter 4, “Alerting Users,” enable you to select actions from a short list of options (usually between two and five options) and can be seen in use in the Photos and Mail applications for sharing and filing data. Figure 3-10 Create a basic two-button menu for simple iPhone applications by adding custom buttons to a UINavigationController. Note You can add images in addition to or instead of text to the UIButtons used in your navigation bar. Recipe 3-1 Creating a Two-Item Menu Using a Navigation Controller - (void) goRed { contentView.backgroundColor = [UIColor colorWithRed: 1.0f green:0.45f ➥blue:0.45f alpha:1.0f];
Slide 118: Recipe: Adding a Segmented Control 95 Recipe 3-1 } Continued - (void) goBlue { contentView.backgroundColor = [UIColor colorWithRed: 0.45f green:0.45f ➥blue:1.0f alpha:1.0f]; } - (void)loadView { contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] ➥applicationFrame]]; self.view = contentView; contentView.backgroundColor = [UIColor whiteColor]; [contentView release]; // Add a left button self.navigationItem.leftBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Red" style:UIBarButtonItemStylePlain target:self action:@selector(goRed)] autorelease]; // Add a right button self.navigationItem.rightBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Blue" style:UIBarButtonItemStylePlain target:self action:@selector(goBlue)] autorelease]; } Recipe: Adding a Segmented Control The preceding recipe showed how to use the two available button slots in your navigation bar to build mini-menus. Recipe 3-2 expands on that idea by introducing a fouritem UISegmentedControl and adding it to a navigation bar’s custom title view, as shown in Figure 3-11.When tapped, each item updates the main view with its number. The key thing to pay attention to in this recipe is the momentary attribute assigned to the segmented control.This transforms the interface from a radio button style into an actual menu, where items can be selected independently and more than once. So after
Slide 119: 96 Chapter 3 View Controllers tapping item three, for example, you can tap it again.That’s an important behavior for menu interaction. Unlike Recipe 3-1, all items in the segmented control trigger the same action (in this case, segmentAction:). Determine which action to take by querying the control for its selectedSegmentIndex and matching that value to the appropriate behavior. Figure 3-11 Adding a segmented control to the custom title view enables you to build a multi-item menu. Notice that no items remain highlighted even after an action takes place. (In this case, the three button was pressed.) Recipe 3-2 Adding a Segmented Control to the Navigation Bar - (void)loadView { // Set up the content view contentView = [[UITextView alloc] initWithFrame:[[UIScreen mainScreen] ➥applicationFrame]]; contentView.autoresizesSubviews = YES; contentView.textAlignment = UITextAlignmentCenter; contentView.font = [UIFont fontWithName:@"Georgia" size:64.0f]; contentView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | ➥UIViewAutoresizingFlexibleHeight); [contentView setEditable:NO]; self.view = contentView; [contentView release];
Slide 120: Recipe: Adding a UIToolbar to a Navigation Bar 97 Recipe 3-2 Continued // Build the Segmented Control NSArray *buttonNames = [NSArray arrayWithObjects:@"One", @"Two", @"Three", ➥@"Four", nil]; UISegmentedControl* segmentedControl = [[UISegmentedControl alloc] ➥initWithItems:buttonNames]; segmentedControl.momentary = YES; [contentView setText:@""]; // Customize the Segmented Control segmentedControl.autoresizingMask = UIViewAutoresizingFlexibleWidth; segmentedControl.segmentedControlStyle = UISegmentedControlStyleBar; segmentedControl.frame = CGRectMake(0, 0, 400, 30); [segmentedControl addTarget:self action:@selector(segmentAction:) ➥forControlEvents:UIControlEventValueChanged]; // Add the control to the navigation bar self.navigationItem.titleView = segmentedControl; [segmentedControl release]; } -(void) segmentAction: (id) sender { switch([sender selectedSegmentIndex] + 1) { case 1: [contentView setText:@"\n\nOne"]; break; case 2: [contentView setText:@"\n\nTwo"]; break; case 3: [contentView setText:@"\n\nThree"]; break; case 4: [contentView setText:@"\n\nFour"]; break; default: break; } } Recipe: Adding a UIToolbar to a Navigation Bar This next recipe builds on the essence of Recipe 3-2, which used a segment control in the navigation bar and takes it a step further. Recipe 3-3 adds a UIToolbar into the navigation item’s custom title view and adds it to the basic interface seen in Recipe 3-1. This accomplishes two things: It adds the power of a toolbar without taking up space at the bottom of the screen. It works without interfering with the two core button slots of the navigation bar. n n
Slide 121: 98 Chapter 3 View Controllers Clutter should be a concern when using this approach. Figure 3-12 shows the updated interface, including both the menu buttons and the toolbar while retaining a clean look.The toolbar uses flexible spaces to the left and right of the arrows to center the controls and maintain a simple presentation. Also beware of landscape presentation. The toolbar height, which works perfectly with the portrait navigation bar, might not match the landscape bar in newer SDK releases. Note The two arrows use custom art, up.png and down.png, which are loaded from the application bundle at runtime and added to the toolbar buttons. Created in Photoshop, they’re basic PNG images, white on a clear background, saved with transparency. Figure 3-12 A well-designed custom toolbar takes advantage of the space between navigation bar buttons while freeing up room at the bottom of the screen. Recipe 3-3 Adding a Toolbar into the Custom Title View - (void)loadView { // Set up the text view to show the current value contentView = [[UITextView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; contentView.autoresizesSubviews = YES;
Slide 122: Recipe: Adding a UIToolbar to a Navigation Bar 99 Recipe 3-3 Continued contentView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight); contentView.editable = NO; contentView.textAlignment = UITextAlignmentCenter; contentView.font = [UIFont fontWithName:@"American Typewriter" size:120]; self.view = contentView; [contentView release]; // Initialize at 50 [contentView setText:@"\n50"]; value = 50; // The app style is black self.navigationController.navigationBar.barStyle = UIBarStyleBlackTranslucent; NSMutableArray *buttons = [[NSMutableArray alloc] init]; UIBarButtonItem *flexibleSpaceItem; flexibleSpaceItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem: UIBarButtonSystemItemFlexibleSpace target:nil action:NULL]; [buttons addObject:flexibleSpaceItem]; [flexibleSpaceItem release]; // Add the up and down items UIBarButtonItem *item; item = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"down.png"] style:UIBarButtonItemStylePlain target:self action:@selector(decrement:)]; [buttons addObject:item]; [item release]; item = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"up.png"] style:UIBarButtonItemStylePlain target:self action:@selector(increment:)]; [buttons addObject:item]; [item release]; flexibleSpaceItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem: UIBarButtonSystemItemFlexibleSpace
Slide 123: 100 Chapter 3 View Controllers Recipe 3-3 Continued target:nil action:NULL]; [buttons addObject:flexibleSpaceItem]; [flexibleSpaceItem release]; UIToolbar *toolbar = [[UIToolbar alloc] init]; toolbar.barStyle = UIBarStyleBlackOpaque; [toolbar setItems:buttons animated:YES]; [toolbar sizeToFit]; self.navigationItem.titleView = toolbar; [toolbar release]; // Add a left button self.navigationItem.leftBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Red" style:UIBarButtonItemStylePlain target:self action:@selector(goRed)] autorelease]; // Add a right button self.navigationItem.rightBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Blue" style:UIBarButtonItemStylePlain target:self action:@selector(goBlue)] autorelease]; } -(void) increment: (id) sender { [contentView setText:[NSString stringWithFormat:@"\n%d", ++value]]; } -(void) decrement: (id) sender { [contentView setText:[NSString stringWithFormat:@"\n%d", —value]]; } Recipe: Navigating Between View Controllers In addition to providing spiffy menus, navigation controllers do the job they are designed to do: managing hierarchy as you navigate between views. Recipe 3-4 introduces the navigation controller as an actual navigation controller, pushing views on the stack.These views consist of three UIViewController subclasses, each with an
Slide 124: Recipe: Navigating Between View Controllers 101 identifying color: lime, pink, and orange. In real use, you’d use more meaningful view controllers.This sample demonstrates things at their simplest level. Here are a couple of points to keep in mind about this recipe: The navigation controller automatically creates the Back button shown in Figure 3-13 (Lime) as an effect of pushing the new (Orange) controller from the (root) Lime controller.The rightmost button (Pink) triggers navigation to the next controller by calling pushViewController: animated:.When pushed, the next Back button would read Orange. The interface works in both landscape and portrait orientations.When testing, you may want to try out both styles. In the Simulator, choose Hardware, Rotate Left (Command-Left arrow) or Hardware, Rotate Right (Command-Right arrow) to see this in action. n n Figure 3-13 The navigation controller automatically creates Back and Forward buttons. Recipe 3-4 Drilling Through Views with UINavigationController @implementation OrangeController - (id) init { // The view controller title sets the name for back buttons // once it’s been pushed if (self = [super init]) self.title = @"Orange";
Slide 125: 102 Chapter 3 View Controllers Recipe 3-4 } Continued return self; - (void) loadButton { // Create the button that activates the switch self.navigationItem.rightBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Pink" style:UIBarButtonItemStylePlain target:self action:@selector(switch:)] autorelease]; } - (void) loadView { [super loadView]; contentView.backgroundColor = ORANGE; } - (void) switch: (id) sender { // On a button press, push the next controller into place [[self navigationController] pushViewController:[[PinkController alloc] init] ➥animated:YES]; } @end Popping Back to the Root Although you’ll usually want to pop to the previous view controller upon hitting the Back button, be aware that there are times you’ll want to pop the entire stack instead. For example, you might have just given an interactive quiz, or a museum visitor might have finished his walking tour. For both cases, it makes little sense to move back up a long complex tree a screen at a time. Instead, use popToRootViewControllerAnimated: to return all the way back to the root or popToViewController: animated: to stop somewhere short of the root.These pop view controllers until either the root or the specified controller becomes the top controller, updating the display accordingly. Loading a View Controller Array You can also create and assign an NSArray of UIViewController objects to a UINavigationController’s viewControllers property.The top (that is, active)
Slide 126: Tab Bars 103 viewController occupies the last position (n-1) in that array while the root object lives at index 0. Arrays are handy when jumping within a conceptual tree. For example, you might be navigating directories and then need to jump through a symbolic link to somewhere else. By setting the entire array, you avoid the detail work of popping and then pushing the stack. View controller arrays also help restore previous states after quitting and then returning to an application. Store a state list to your local defaults and then re-create the same array on launch. Assign the re-created array to viewControllers and you return your user to the same place he or she left from. Tab Bars The UITabBarController class enables users to move between multiple view controllers and to customize the bar at the bottom of the screen.This is best seen in the YouTube and iPod applications. Both offer one-tap access to different views, and both offer a More button leading to user selection and editing of the bottom bar. With tab bars, you don’t push views the way you do with navigation bars. Instead, you assemble a collection of controllers (they can individually be UIViewControllers, UINavigationControllers, or any other kind of view controllers) and add them into a tab bar. Just set the bar’s viewControllers property. It really is that simple. Cocoa Touch does all the rest of the work for you. Set allowsCustomizing to YES to enable user reordering of the bar. Recipe 3-5 creates 11 simple view controllers of the BrightnessController class. This class builds a UIView and sets it background to a specified gray level, in this case from 0% to 100% in steps of 10%.These 11 view controllers, in the form of an array, become the options a user can navigate through and select from, as shown in Figure 3-14. Notice that this recipe adds those 11 controllers twice.The first time assigns them to the list of view controllers available to the user: tbarController.viewControllers = controllers; The second time specifies that the user can select from the entire list when interactively customizing the bottom tab bar: tbarController.customizableViewControllers = controllers; The second line is optional, the first mandatory. After setting up the view controllers, you can add all or some to the customizable list. If you don’t, you’ll still be able to see the extra view controllers using the More button, but users won’t be able to include them in the main tab bar on demand. Note that art appears inverted in color on the More screen. According to Apple, this is the expected and proper behavior.They have no plans to change this. It does provide an interesting view contrast when your 100% white swatch appears as pure black on that screen.
Slide 127: 104 Chapter 3 View Controllers Figure 3-14 Tab bar controllers enable users to pick view controllers from a bar at the bottom of the screen (left side of the figure) and to customize the bar from a list of available view controllers (right side of the figure). Recipe 3-5 Creating a Tab View Controller @interface BrightnessController : UIViewController { UIView *contentView; int brightness; } @end @implementation BrightnessController -(BrightnessController *) initWithBrightness: (int) aBrightness { self = [super init]; brightness = aBrightness; self.title = [NSString stringWithFormat:@"%d%%", brightness * 10]; [self.tabBarItem initWithTitle:self.title image:createImage(((float) brightness / 10.0f)) tag:NULL]; return self; } - (void)loadView { // Create each view with the given brightness contentView = [[UIView alloc] init]; float percent = brightness * 0.1;
Slide 128: Tab Bars 105 Recipe 3-5 Continued contentView.backgroundColor = [UIColor colorWithRed:percent green:percent ➥blue:percent alpha:1.0]; contentView.autoresizesSubviews = YES; contentView.autoresizingMask = (UIViewAutoresizingFlexibleWidth | ➥UIViewAutoresizingFlexibleHeight); self.view = contentView; [contentView release]; } -(void) dealloc { [contentView release]; [super dealloc]; } @end @interface SampleAppDelegate : NSObject <UIApplicationDelegate, ➥UITabBarControllerDelegate> { } @end @implementation SampleAppDelegate - (void)applicationDidFinishLaunching:(UIApplication *)application { UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] ➥bounds]]; // Create the array of UIViewControllers NSMutableArray *controllers = [[NSMutableArray alloc] init]; for (int i = 0; i < 11; i++) { BrightnessController *bControl = [[BrightnessController alloc] initWithBrightness:i]; UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:bControl]; nav.navigationBar.barStyle = UIBarStyleBlackTranslucent; [controllers addObject:nav]; [bControl release]; [nav release]; } UITabBarController *tbarController = [[UITabBarController alloc] init]; tbarController.viewControllers = controllers; tbarController.customizableViewControllers = controllers;
Slide 129: 106 Chapter 3 View Controllers Recipe 3-5 Continued tbarController.delegate = self; tbarController.allowsCustomizing = YES; [window addSubview:tbarController.view]; [window makeKeyAndVisible]; [controllers release]; } - (void)dealloc { [super dealloc]; } @end Summary This chapter introduced the UIViewController, UINavigationController, and UITabBarController classes and showed how to use them.These classes handle view management and user navigation. Between them, developers can expand virtual interaction space and create multipage interfaces as demanded by their applications. Between the walk-through and recipes, you’ve learned how you can connect view controllers to interfaces designed in Interface Builder and how to create interfaces entirely within Xcode. Before moving on to the next chapter, here are a few points to consider about view controllers: Interface Builder excels at laying out the content of UIView instances. Use its tools to connect those instances to the view controllers in your program and use Interface Builder to refine WYSIWYG-style interfaces like the temperature converter example covered in this chapter. Know when Interface Builder isn’t the right solution.When you’re building tab bars and navigation controllers with minimal window design (such as for tablebased or text-based applications), you don’t especially need IB’s view layout tools. When skipping IB, make sure to delete the XIB file from your project and remove the main NIB window key from Info.plist. n n n n Use navigation trees to build hierarchical interfaces.They work great for looking at file structures or building a settings tree.When you think “disclosure view” or “preferences,” consider pushing a new controller onto a navigation stack. Don’t be afraid to use conventional UI elements in unconventional ways. A large part of this chapter covered innovative uses for the UINavigationController that didn’t involve any navigation.The tools are there for the using.
Slide 130: 4 Alerting Users At times, you need to grab your user’s attention. New messages might arrive or the system status might change.You might want to tell your user that there’s going to be a wait before anything more happens—or that the wait is over and it’s time to come back and pay attention.The iPhone offers many ways to provide that heads-up to the user: from alerts and progress bars to audio pings and status bar updates. In this chapter, you discover how to build these indications into your applications and expand your user-alert vocabulary.You’re about to see real-life examples that showcase these classes and discover how to make sure your user pays attention at the right time. Talking Directly to Your User Through Alerts UIActionSheet and UIAlertView objects speak to your user.They pop up or scroll in above other views to deliver their message.These lightweight classes add two-way dialog to your apps. Alerts visually “speak” to users and can prompt them to reply.You present your alert onscreen, get user acknowledgment, and then dismiss the alert to move on with other tasks. If you think that alerts are nothing more than messages with an attached OK button (as in Figure 4-1), think again. UIAlertSheet objects provide incredible versatility— assuming that Apple continues to let you access that incredible versatility.With alert sheets, you can actually build menus, text input, queries, and more. Unfortunately, much of this behavior falls into the undocumented or barely supported category. In this chapter’s recipes, you see how to create a wide range of useful alerts that you can use in your own programs. Much of the functionality covered in this chapter was removed from the official SDK yet remains within the public frameworks. Because this chapter relies so heavily on “unofficial” calls, think long and hard about the trade-offs between reliability and power programming. Apple discourages developers from using private routines because they change them at will. But the bottom line is the same story as with Mac OS X. If you figure out how to use private routines in public frameworks, you can use them.You cross the line when you start accessing private frameworks in your applications.
Slide 131: 108 Chapter 4 Alerting Users Note In early releases of the iPhone firmware, UIActionSheet and UIAlertView were implemented by the same class, UIAlertSheet. This one class provided both pop-up alert and menu functionality. Then Apple replaced alert sheets with UIModalView and subclassed these new objects from that base class. Later, Apple removed UIModalView, and in new versions of the SDK, UIActionSheet and UIAlertView are no longer derived from that class. (They both descend from UIView.) Like their predecessors, they remain siblings in their behavior and use similar underlying technology to present themselves onscreen. Logging Your Results Due to their sample nature, most of these recipes use printf to output their results into a viewable format. During the initial SDK beta period,printf provided the most reliable way to examine internal program data.NSLog() is now fully implemented and stable in recent iPhone SDK releases. In addition, here are a few tricks you may want to use. Redirecting stderr The standard freopen() function redirects stderr output to a log file of your choice. Supply it a local path. Here, logPath is a standard NSString such as @"/tmp/mylog", which is converted to a local file system representation. After this call, all stderr results (this includes NSLog) go directly to your log file. Use "w" (write) rather than "a" (append) to restart the log when your program runs: freopen([logPath fileSystemRepresentation], "a", stderr); Building a Custom Log Function Building your own log function allows you to add functionality that goes beyond standard NSLog. Here is a basic log function that mimics NSLog‘s functionality. It’s not hard to adapt this to produce, for example, an alert notification or a text view update rather than a print to stderr: #include <stdarg.h> void dolog(id formatstring,...) { va_list arglist; if (formatstring) { va_start(arglist, formatstring); id outstring = [[NSString alloc] initWithFormat:formatstring arguments:arglist]; fprintf(stderr, "%s\n", [outstring UTF8String]); [outstring release]; va_end(arglist); } }
Slide 132: Talking Directly to Your User Through Alerts 109 Building Alerts To create alert sheets, allocate a UIAlertView object. Initialize it with a title and a button array, along with a few other options.The title is an NSString, and the button array includes NSStrings, where each string represents a single button. Listing 4-1 creates a very simple alert, as shown in Figure 4-1. When working with alerts, space is often at a premium. Placing buttons on a single line minimizes the alert height and is the default presentation.When you define more buttons, they’re added side by side. So, limit the number of buttons you add at any time to no more than three or four. Fewer buttons work better, one or two being ideal. UIAlertView objects provide no visual “default” button highlights. In the iPhone context, button highlights are more confusing than helpful. (For example, should users press on the light button or the dark?) There’s no way to match the interface to user expectations because the presentation is ambiguous. So unlike OS X, Apple has omitted highlights in newer iPhone firmware. Note The Cancel button appears at the bottom of menus and at the left of pop-up alerts. Listing 4-1 Creating a Basic Alert UIAlertView *baseAlert = [[UIAlertView alloc] initWithTitle:@"Alert" message:@"" delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil]; Figure 4-1 Use the UIAlertView class to build simple pop-up alerts.
Slide 133: 110 Chapter 4 Alerting Users Unless you have some compelling reason to do otherwise, set the delegate to your primary UIViewController object.The delegate implements the UIAlertViewDelegate protocol. UIAlertView instances require this delegate support to handle button taps, at a minimum. Delegate methods enable you to customize your responses when different buttons are pressed.You can actually omit that delegate support if all you need to do is throw up some message with an OK button. After the user has seen and interacted with your alert, they raise the following delegate method call: alertView: clickedButtonAtIndex:. From this call, you can determine which button was pressed and recover any options that have been set on the sheet. Button numbering begins with zero. Displaying the Alert Use the show method to tell your alert to appear onscreen (that is, [myAlert show]). When shown, the alert works in a modal fashion.That is, it dims the screen behind it and blocks user interaction with your application.This modal interaction continues until your user acknowledges the alert through a button tap, typically by selecting OK or Cancel. Note After creating the alert sheet, you may customize the alert by updating its message. That’s optional text that appears below the alert title and above its buttons. Other customizable properties include title, delegate, and visible. Recipe: Creating Multiline Button Displays By default, iPhone alerts present their buttons in a single line. Figure 4-2 shows this standard look on the left.You can override the single row presentation using an undocumented call.This call creates a multiline alert, as shown on the right. Use setNumberOfRows: to build alerts that use one row per button, as demonstrated in Listing 4-2. Supply a single argument, an integer, specifying the requested number of rows. Note See Chapter 1, “Introducing the iPhone SDK,” for further discussion about using undocumented calls and features in your programs. Earlier versions of the iPhone software worked in reverse.The standard was originally multiple rows, and you had to use setNumberOfRows: to get the phone to move the buttons onto a single line. The sample created by Recipe 4-1 pop ups its alert midscreen, dimming the screen around it. Because it runs modal by default, everything waits until the user taps the OK
Slide 134: Recipe: Creating Multiline Button Displays 111 button. Once tapped, the alert closes, passing control to the modalView: clickedButtonAtIndex: delegate method.This method, as defined here, does little more than print out the tapped button’s number. Note You can disable background dimming using setDimsBackground:NO. This is another undocumented call. I can’t recommend it for general use. It breaks the Apple human interface standards and may confuse your user as to whether the background can be tapped during the lifetime of the alert. Figure 4-2 An undocumented UIKit call allows you to select whether to lay out your buttons in a row or a column. Recipe 4-1 Creating UIAlertViews with One Button per Line - (void) presentSheet { UIAlertView *baseAlert = [[UIAlertView alloc] initWithTitle:@"Alert" message:@"Please select a button" delegate:self cancelButtonTitle:nil otherButtonTitles:@"One", @"Two", @"Three", nil]; [baseAlert setNumberOfRows:3]; [baseAlert show]; }
Slide 135: 112 Chapter 4 Alerting Users Recipe 4-1 Continued - (void)alertView:(UIAlertView *)alertView ➥clickedButtonAtIndex:(NSInteger)buttonIndex { printf("User Pressed Button %d\n", buttonIndex + 1); [alertView release]; } Recipe: Autotimed No-Button Alerts No-button alerts present a special challenge because they do not properly call back to a delegate method.They do not autodismiss, even when tapped. Figure 4-3 shows a simple no-button alert. As you can see from this screenshot, removing buttons produce awkwardlooking alerts.You can enhance presentation by adjusting the message text. Add carriage returns (@“\n”) to balance the bottom (where buttons normally go) with the spacing at the top. Because alerts run modally, you need to add a safeguard to ensure that the alert goes away at some point and users can continue using their iPhone. A simple NSTimer that dismisses the alert after a set period of time must return control back to the standard GUI. Recipe 4-2 creates an alert and dismisses it using a timer and either the undocumented dismiss method or the UIAlertView class’s dismissWithClickedButtonIndex: animated: method. Figure 4-3 Use the undocumented dismiss method to return control to your program after displaying a button-free UIAlertView. It helps to balance the extra bottom space where the missing buttons would go by adding carriage returns to the message property.
Slide 136: Recipe: Soliciting Text Input from the User 113 Recipe 4-2 Creating No-Button UIAlertViews with Timer Fail-Safe - (void) performDismiss: (NSTimer *)timer { [baseAlert dismissWithClickedButtonIndex:0 animated:NO]; } - (void) presentSheet { baseAlert = [[UIAlertView alloc] initWithTitle:@"Alert" message:@"Message to user with asynchronous information" delegate:self cancelButtonTitle:nil otherButtonTitles: nil]; [NSTimer scheduledTimerWithTimeInterval:3.0f target:self selector: ➥@selector(performDismiss:) userInfo:nil repeats:NO]; [baseAlert show]; } Recipe: Soliciting Text Input from the User Leaving official SDK calls aside, alert views provide an especially simple way to prompt your user for text.The UIAlertView class takes total command of presenting and dismissing an associated keyboard. All you have to do is add the text input fields, tell the alert how to handle them, and let it take care of the rest. To add a text field, use the undocumented addTextFieldWithValue: label: call. Send the default text as the first argument and the text that displays in an otherwiseempty field as the second. Figure 4-4 shows both a filled and empty field. You can recover each field via [alert textFieldAtIndex:0]and then pull the text from the text field with text. Because each field is addressable, you can set its attributes before presenting the alert. Customize the autocaps, the autocorrection, and the preferred keyboard, as demonstrated in Recipe 4-3. Space is an important consideration. If you manage your space carefully, you can place the alert onscreen leaving enough room for the keyboard to present itself. By skipping a title and body text, you can fit three (but not four) text entry fields onscreen at once. Two fields is a more practical maximum, as Figure 4-4 reveals. Recipe 4-3 Using UIAlertView to Solicit Text from Users - (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { printf("User Pressed Button %d\n", buttonIndex + 1); printf("Text Field 1: %s\n", [[[modalView textFieldAtIndex:0] text] ➥cStringUsingEncoding:1]);
Slide 137: 114 Chapter 4 Alerting Users Figure 4-4 Using careful space management and omitting the title and body text, you can add up to three text entry fields to a UIAlertSheet at once. You probably want to limit your UIAlertSheets to one or two text fields. Recipe 4-3 Continued printf("Text Field 2: %s\n", [[[modalView textFieldAtIndex:1] text] ➥cStringUsingEncoding:1]); [alertView release]; } - (void) presentSheet { UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Enter Information" message:@"Specify the Name and URL" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:@"OK", nil]; [alert addTextFieldWithValue:@"" label:@"Enter Name"]; [alert addTextFieldWithValue:@"http://" label:@"Enter URL"]; // Name field UITextField *tf = [alert textFieldAtIndex:0]; tf.clearButtonMode = UITextFieldViewModeWhileEditing; tf.keyboardType = UIKeyboardTypeAlphabet; tf.keyboardAppearance = UIKeyboardAppearanceAlert;
Slide 138: Recipe: Presenting Simple Menus 115 Recipe 4-3 Continued tf.autocapitalizationType = UITextAutocapitalizationTypeWords; tf.autocorrectionType = UITextAutocorrectionTypeNo; // URL field tf = [alert textFieldAtIndex:1]; tf.clearButtonMode = UITextFieldViewModeWhileEditing; tf.keyboardType = UIKeyboardTypeURL; tf.keyboardAppearance = UIKeyboardAppearanceAlert; tf.autocapitalizationType = UITextAutocapitalizationTypeNone; tf.autocorrectionType = UITextAutocorrectionTypeNo; [alert show]; } Recipe: Presenting Simple Menus When it comes to menus, UIActionSheet instances supply the iPhone answer.They slide choices, basically a list of buttons representing possible actions, onto the screen and wait for the user to respond. Action sheets are different from pop-ups. Pop-ups stand apart from the interface and are better used for demanding attention. Menus slide into a view and better integrate with ongoing application work. Cocoa Touch supplies two ways to present menus: showInView. Presenting your sheet in a view is pretty much the ideal way to use menus and is the method used here.This method slides the menu up from the exact bottom of the view (see Figure 4-5). showFromToolBar: and showFromTabBar. When working with toolbars, tab bars, or any other kinds of bars that provide those horizontally grouped buttons that you see at the bottom of many applications, these methods align the menu with the top of the bar and slide it out exactly where it should be. Recipe 4-4 shows how to initialize and present a simple UIActionSheet instance. Its initialization method introduces a concept missing from UIAlertView: the destructive button. Colored in red, a destructive button indicates an action from which there is no return, such as permanently deleting a file (see Figure 4-5). Its bright red color warns the user about the choice. Obviously, this option should be used sparingly. n n Note Missing in action sheets, at least as far as the official SDK is concerned, is the UIAlertView’s message. Action sheet instances do not officially support adding a message in addition to presenting a title. In reality, messages are implemented, even if they’re not especially pretty. Use the undocumented setMessage: call to add a message to your menu. When used, messages appear below the sheet title, in slightly larger text.
Slide 139: 116 Chapter 4 Alerting Users Figure 4-5 Use showInView: to create simple menu presentations. The menu slides in from the bottom of the view. Although the “Delete File” menu button appears gray here, it is red on your iPhone and indicates permanent actions with possible negative consequences to your users. Recipe 4-4 Presenting a Menu - (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex { printf("User Pressed Button %d\n", buttonIndex + 1); [actionSheet release]; } - (void) presentSheet { UIActionSheet *menu = [[UIActionSheet alloc] initWithTitle: @"File Management" delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:@"Delete File" otherButtonTitles:@"Rename File", @"Email File", nil]; [menu showInView:contentView]; }
Slide 140: Recipe: Invoking the Basic Undocumented UIProgressHUD 117 “Please Wait”: Showing Progress to Your User Waiting is an intrinsic part of the computing experience and will remain so for the foreseeable future. It’s your job as a developer to communicate that fact to your users. Cocoa Touch provides several classes that tell your user to wait for a process to complete.These progress indicators come in two forms: as a spinning wheel that persists for the duration of its presentation; and as a bar, which fills from left to right as your process moves forward from start to end.The classes that provide these indications are as follows: UIActivityIndicatorView. A progress indicator offers a spinning circle that tells your user to wait without providing specific information about its degree of completion.The iPhone activity indicator is small, but its live animation catches the user’s eye and is best-suited for quick disruptions in a normal application. UIProgressView. This view presents a progress bar.The bar provides concrete feedback as to how much work has been done and how much remains while occupying a relatively small onscreen space. It presents as a thin, horizontal rectangle that fills itself from left to right as progress takes place.This classic user interface element works best for long delays, where users want to know to what degree the job has finished. And from the undocumented features point of view, you have the following: n n n UIProgressHUD. The undocumented “heads up display” version of the progress indicator floats over all other views within a window and adds a status message to the basic progress indicator.The HUD provides a middle ground between the bar and the simple indicator.You do not need to quantify your progress, the way you do with progress bars, but the associated text enables you to narrate your progress. Progress HUDs work especially well when you want to indicate what’s happened along a process (for example, “Contacting Server,” “Authenticating,” “Requesting Data,” and so forth). Recipe: Invoking the Basic Undocumented UIProgressHUD The UIProgressHUD class overlays your window with a status dialog.This dialog contains a rotating progress indicator and a short message that you specify. As far as programming goes, all you have to do is instantiate the object, initialize it using your main window, and tell it to go by sending show:YES. Figure 4-6 shows a UIProgressHUD display in action, and Recipe 4-5 shows the code that created that display. UIProgressHUD enables you to update its text as needed. Send a new setText: message at any time.When you’ve finished, dismiss it using show:NO.You can adjust the font size via setFontSize: if needed, but I urge you to keep your messages short and to the point.
Slide 141: 118 Chapter 4 Alerting Users Note It’s disappointing that Apple did not include this as a standard SDK class. I’ve presented the workaround here. By the time this book publishes, hopefully Apple will have added it back to Cocoa Touch. Figure 4-6 The UIProgressHUD’s name means that it is an HUD. It adds a progress overlay above your window. You tell it when to show, when to hide, and what to say. When using HUD displays with data intense code, you’ll want to let it run in its own thread so the UI updates do not block.To do this, use NSThread’s detatchThreadSelector: toTarget: withObject: method. Use separate threads to start it going, to update the HUD’s text, and to dismiss the HUD when finished. Recipe 4-5 Creating a UIProgressHUD for Your Window @interface UIProgressHUD : NSObject - (void) show: (BOOL) yesOrNo; - (UIProgressHUD *) initWithWindow: (UIView *) window; - (void) setText: (NSString *) theText; @end - (void) killHUD: (id) aHUD { [aHUD show:NO]; [aHUD release];
Slide 142: Recipe: Using UIActivityIndicatorView 119 Recipe 4-5 Continued } - (void) presentSheet { id HUD = [[UIProgressHUD alloc] initWithWindow:[contentView superview]]; [HUD setText:@"Downloading File. Please wait."]; [HUD show:YES]; [self performSelector:@selector(killHUD:) withObject:HUD afterDelay:5.0]; } Recipe: Using UIActivityIndicatorView UIActivityIndicatorView instances offer lightweight views that display a standard rotating progress wheel.The keyword to keep in mind when working with these views is small. The sharpest display for most indicator styles occurs at a view size of just 20 by 20 pixels. Any larger, and the indicator starts to blur. Figure 4-7 shows a 40-pixel version. You need not center the indicator on the screen. Place it wherever it works best for you. As a clear-backed view, the indicator will blend over whatever backdrop view lies behind it.The predominant color of that backdrop helps select which style of indicator to use. For general use, just add the activity indicator as a subview to the window, view, toolbar or navigation bar you want to overlay. Allocate the indicator and initialize it with a frame, preferably centered within whatever parent view you’re using. Start the indicator in action by updating its animating property to YES.To stop, set the property to NO. Cocoa Touch takes care of the rest, hiding the view when not in use. The iPhone offers several different styles of the UIActivityIndicatorView class. UIActivityIndicatorViewStyleWhite and UIActivityIndicatorViewStyleGray are the cleanest.The white version looks best against a black background, and the gray (shown in Figure 4-7) looks best against white. It’s a thin, sharp style.Take care when choosing whether to use white or gray. An all-white presentation will not show at all against a white backdrop. Unfortunately,UIActivityIndicatorViewStyleWhiteLarge is available only for use on dark backgrounds. It provides the largest, clearest indicator. Recipe 4-6 shows the code used to create these simple UIActivityIndicatorView instances. Recipe 4-6 Adding a UIActivityIndicatorView to Your Program - (void) performAction { if (progressShowing) [activityIndicator stopAnimating]; else [activityIndicator startAnimating]; progressShowing = !progressShowing; } - (void)loadView {
Slide 143: 120 Chapter 4 Alerting Users Recipe 4-6 Continued contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] ➥applicationFrame]]; self.view = contentView; contentView.backgroundColor = [UIColor whiteColor]; [contentView release]; // Add an action button self.navigationItem.rightBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Do It" style:UIBarButtonItemStylePlain target:self action:@selector(performAction)] autorelease]; // Add the progress indicator but do not start it progressShowing = NO; activityIndicator = [[UIActivityIndicatorView alloc] ➥initWithFrame:CGRectMake(0.0f, 0.0f, 32.0f, 32.0f)]; [activityIndicator setCenter:CGPointMake(160.0f, 208.0f)]; [activityIndicator ➥setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleGray]; [contentView addSubview:activityIndicator]; [activityIndicator release]; } Figure 4-7 The UIActivityIndicatorView class provides a simple rotating wheel that’s meant to display at relatively small sizes.
Slide 144: Recipe: Building a UIProgressView 121 Recipe: Building a UIProgressView Progress views enable your users to follow task progress as it happens rather than just saying “Please wait.”They present bars that fill from left to right.These bars indicate the degree to which a task has finished. Progress bars work best for long waits where providing state feedback enables your users to retain the feel of control. To create a progress view, allocate it and set its frame.To use the bar, issue setProgress:.This takes one argument, a floating-point number that ranges between 0.0 (no progress) and 1.0 (finished). Progress view bars come in two styles: basic white or light gray.The setStyle: method chooses the kind you prefer. Unlike the other kinds of progress indicators, it’s completely up to you to show and hide the progress bar’s view.There’s no setVisible: method. I like adding progress bars to action sheets.This simplifies both bringing them onto the screen and dismissing them. Another advantage is that when alert sheets display, the rest of the screen dims.This forces a modal presentation as your task progresses. Users cannot interact with the GUI until you dismiss the alert. Recipe 4-7 shows a UIActionSheet/UIProgressView sample that produces the display shown in Figure 4-8. Use UIProgressView instances to track progress over an extended delay. Adding them to a UIActionSheet simplifies their presentation and dismissal. Figure 4-8 This recipe uses the undocumented setNumberOfRows: call.To stay within SDK standards, add a bunch of new lines (\n) to the title.
Slide 145: 122 Chapter 4 Alerting Users Note When embedding a progress bar into an action sheet, you need to implement the UIActionSheet delegate protocol. Adding a button click method satisfies the required methods for that protocol, even if the method itself does nothing. Recipe 4-7 Adding a Progress Bar to an Alert Sheet @interface UIActionSheet (extended) - (void) setNumberOfRows: (NSInteger) rows; @end @implementation HelloController // This callback fakes progress via setProgress: - (void) incrementBar: (id) timer { amountDone += 1.0f; [progbar setProgress: (amountDone / 20.0)]; if (amountDone > 20.0) {[baseSheet dismissWithClickedButtonIndex:0 ➥animated:YES]; [timer invalidate];} } // Dismiss the action sheet backdrop used here - (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex { [actionSheet release]; } // Load the progress bar onto an actionsheet backing - (void) presentSheet { if (!baseSheet) { baseSheet = [[UIActionSheet alloc] initWithTitle:@"Please Wait" delegate:self cancelButtonTitle:nil destructiveButtonTitle: nil otherButtonTitles: nil]; [baseSheet setNumberOfRows:5]; [baseSheet setMessage:@"Updating Internal Databases"]; progbar = [[UIProgressView alloc] initWithFrame:CGRectMake(50.0f, 70.0f, ➥220.0f, 90.0f)]; [progbar setProgressViewStyle: UIProgressViewStyleDefault];
Slide 146: Recipe: Adding Custom, Tappable Overlays 123 Recipe 4-7 Continued [baseSheet addSubview:progbar]; [progbar release]; } // Create the demonstration updates [progbar setProgress:(amountDone = 0.0f)]; [NSTimer scheduledTimerWithTimeInterval: 0.5 target: self selector: ➥@selector(incrementBar:) userInfo: nil repeats: YES]; [baseSheet showInView:contentView]; } - (void)loadView { contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] ➥applicationFrame]]; self.view = contentView; contentView.backgroundColor = [UIColor whiteColor]; [contentView release]; // Add an action button self.navigationItem.rightBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Do It" style:UIBarButtonItemStylePlain target:self action:@selector(presentSheet)] autorelease]; } Recipe: Adding Custom, Tappable Overlays When communicating to users, you need not limit yourself to standard (even when undocumented) UIKit objects. Fading an overlay onto a view offers unlimited possibilities.You can throw up text, images, animation, and what have you.You can make the overlay interactive (as shown in this recipe) or allow any taps to fall through to the interface below.You can add simple status information (think white, gray, or black text on a transparent background) or you can build an elaborate presentation.The choice is up to you. Figure 4-9 shows the custom “Please Wait” overlay built in Recipe 4-8. Adding UIView animations, as discussed in Chapter 2, “Views,” smoothes this overlay’s entrance and exit presentations. A tap on the overlay dismisses it, returning you to the interface beneath.This overlay is, as you can see, busy and intended to go over a clean, bright background.To use this kind of overlay with a complicated interface, you might fill in
Slide 147: 124 Chapter 4 Alerting Users the transparent areas with a translucent white, which would partially hide the interface and add a backdrop that allows any message to remain visible. If you want to add an overlay like this and provide your own UIProgressHUD-like backdrop, use care that you match Apple’s overall graphic design. Users are particularly sensitive to errors in custom interface elements. Figure 4-9 Combine transparency with animation to create view overlays that pop. Recipe 4-8 Creating a Custom Animated UIView Overlay @interface PleaseWaitView : UIImageView @end @implementation PleaseWaitView - (PleaseWaitView *) initWithFrame: (CGRect) rect { self = [super initWithFrame:rect]; [self setImage:[UIImage imageNamed:@"PlsWait.png"]]; UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(40.0f, ➥300.0f, 60.0f, 60.0f)]; [self addSubview:imgView]; [imgView release]; // load in the animation cells for the butterfly
Slide 148: Recipe: Adding Custom, Tappable Overlays 125 Recipe 4-8 Continued NSMutableArray *bflies = [[NSMutableArray alloc] init]; for (int i = 1; i <= 17; i++) { NSString *cname = [NSString stringWithFormat:@"bf_%d.png", i]; UIImage *img = [UIImage imageNamed:cname]; if (img) [bflies addObject:img]; } // begin the animation [imgView setAnimationImages:bflies]; imgView.animationDuration = 0.75f; [imgView startAnimating]; [bflies release]; return self; } - (void)touchesBegan: (NSSet *) touches withEvent:(UIEvent *)event { // fade away the overlay CGContextRef context = UIGraphicsGetCurrentContext(); [UIView beginAnimations:nil context:context]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationDuration:1.0]; [self setAlpha:0.0f]; // Complete the animation [UIView commitAnimations]; [pleaseWait setUserInteractionEnabled:YES]; } @end @interface HelloController : UIViewController { UIView *contentView; PleaseWaitView *pleaseWait; } @end @implementation HelloController CGPoint randomPoint() { return CGPointMake(random() % 256, random() % 256); } - (void) moveButterfly: (NSTimer *) timer
Slide 149: 126 Chapter 4 Alerting Users Recipe 4-8 { Continued if ([pleaseWait alpha] == 0.0f) {[timer invalidate]; return;} // Create an animation block around moving the butterfly to a new origin CGContextRef context = UIGraphicsGetCurrentContext(); [UIView beginAnimations:nil context:context]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationDuration:1.0]; // Move the butterfly UIImageView *iv = [[pleaseWait subviews] objectAtIndex:0]; CGRect frame = [iv frame]; frame.origin = randomPoint(); [iv setFrame:frame]; // Complete the animation [UIView commitAnimations]; } - (void) presentSheet { if ([pleaseWait alpha] != 0.0f) return; // Create an animation block around fading in the overlay CGContextRef context = UIGraphicsGetCurrentContext(); [UIView beginAnimations:nil context:context]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationDuration:1.0]; [pleaseWait setAlpha:1.0f]; // Complete the animation [UIView commitAnimations]; // Give life to the butterfly [NSTimer scheduledTimerWithTimeInterval: 4.0f target: self selector: ➥@selector(moveButterfly:) userInfo: nil repeats: YES]; } - (id) init { if (self = [super init]) self.title = @"Hello World"; return self;
Slide 150: Recipe: Building a Scroll-Down Alert 127 Recipe 4-8 } Continued - (void)loadView { contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] ➥applicationFrame]]; self.view = contentView; contentView.backgroundColor = [UIColor whiteColor]; [contentView release]; // reduce retain count by one // Add an action button self.navigationItem.rightBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Do It" style:UIBarButtonItemStylePlain target:self action:@selector(presentSheet)] autorelease]; // Create and hide the "Please Wait" view pleaseWait = [[PleaseWaitView alloc] initWithFrame:[[UIScreen mainScreen] ➥applicationFrame]]; [contentView addSubview:pleaseWait]; [pleaseWait setAlpha:0.0f]; } -(void) dealloc { [pleaseWait release]; [contentView release]; [super dealloc]; } @end Recipe: Building a Scroll-Down Alert Building off the preceding recipe’s animation block, you can apply the same kind of approach to create a more traditional scroll-down alert. Recipe 4-9 animates a view’s frame location to create the illusion that a view has scrolled onscreen.The frame starts offscreen and animates itself onscreen to present itself as shown in Figure 4-10.When the user clicks OK, the process reverses.You can use this method to build any kind of alert. The view in this recipe contains a title, a block of text, and a simple button. Add any UIView elements or controls as needed to your own implementation. An example in Chapter 5, “Basic Tables,” builds on this recipe by adding a user-selectable scrolling table to the slide-down view.