The Core iOS 6 Developer's Cookbook

Erica Sadun is the bestselling author, coauthor, and contributor to several dozen books on programming, digital video and photography, and web design, including the widely popular The iOS 5 Developer’s Cookbook. She currently blogs at TUAW.com, and has blogged in the past at O’Reilly’s Mac Devcenter, Lifehacker, and Ars Technica. In addition to being the author of dozens of iOS-native applications, Erica holds a Ph.D. in Computer Science from Georgia Tech’s Graphics, Visualization and Usability Center. A geek, a programmer, and an author, she’s never met a gadget she didn’t love. When not writing, she and her geek husband parent three geeks-in-training, who regard their parents with restrained bemusement, when they’re not busy rewiring the house or plotting global dominance.

Preface   xxii

1  Gestures and Touches   1
Touches   1
  Phases   2
  Touches and Responder Methods   3
  Touching Views   4
  Multi-Touch   4
  Gesture Recognizers   5
Recipe: Adding a Simple Direct Manipulation Interface   5
Recipe: Adding Pan Gesture Recognizers   7
Recipe: Using Multiple Gesture Recognizers Simultaneously   9
Resolving Gesture Conflicts   12
Recipe: Constraining Movement   13
Recipe: Testing Touches   15
Recipe: Testing Against a Bitmap   17
Recipe: Drawing Touches Onscreen   19
Recipe: Smoothing Drawings   21
Recipe: Using Multi-Touch Interaction   24
Recipe: Detecting Circles   28
Recipe: Creating a Custom Gesture Recognizer   33
Recipe: Dragging from a Scroll View   35
Recipe: Live Touch Feedback   39
  Enabling Touch Feedback    39
  Intercepting and Forwarding Touch Events   40
  Implementing the TOUCHkit Overlay View   41
Recipe: Adding Menus to Views   44
Summary   46

2  Building and Using Controls   49
The UIControl Class   49
  Target-Action   50
  Kinds of Controls   50
  Control Events   51
Buttons   53
Buttons in Interface Builder   54
  Connecting Buttons to Actions   55
Recipe: Building Buttons   55
  Multiline Button Text   58
  Adding Animated Elements to Buttons   58
  Adding Extra State to Buttons   59
Recipe: Animating Button Responses   59
Recipe: Adding a Slider with a Custom Thumb   61
  Customizing UISlider   62
  Adding Efficiency   63
Appearance Proxies   66
Recipe: Creating a Twice-Tappable Segmented Control   69
  Second-Tap Feedback   70
  Controls and Attributes   70
Working with Switches and Steppers   72
Recipe: Subclassing UIControl   73
  Creating Controls   74
  Tracking Touches   74
  Dispatching Events   74
Recipe: Building a Star Slider   77
Recipe: Building a Touch Wheel   80
Recipe: Creating a Pull Control   83
  Discoverability   83
  Testing Touches   85
Recipe: Building a Custom Lock Control   87
Adding a Page Indicator Control   90
Recipe: Creating a Customizable Paged Scroller   93
Building Toolbars   98
Summary   100

3  Alerting the User   101
Talking Directly to Your User Through Alerts   101
  Building Simple Alerts   102
  Alert Delegates   103
  Displaying the Alert   104
  Kinds of Alerts   104
“Please Wait”: Showing Progress to Your User   105
  Using UIActivityIndicatorView   106
  Using UIProgressView   107
Recipe: No-Button Alerts   107
  Building a Floating Progress Monitor   109
Recipe: Creating Modal Alerts with Run Loops   110
Recipe: Using Variadic Arguments with Alert Views   113
Presenting Lists of Options   114
  Scrolling Menus   117
  Displaying Text in Action Sheets   117
Recipe: Building Custom Overlays   117
  Tappable Overlays   119
Recipe: Basic Popovers   119
Recipe: Local Notifications   121
  Best Practices   122
Alert Indicators   123
  Badging Applications   124
Recipe: Simple Audio Alerts   124
  System Sounds   124
  Vibration   125
  Alerts   126
  Delays   126
  Disposing of System Sounds   126
Summary   128

4  Assembling Views and Animations   129
View Hierarchies   129
Recipe: Recovering a View Hierarchy Tree   131
  Exploring XIB and Storyboard Views   132
Recipe: Querying Subviews   133
Managing Subviews   134
  Adding Subviews   134
  Reordering and Removing Subviews   135
  View Callbacks   135
Tagging and Retrieving Views   136
  Using Tags to Find Views   136
Recipe: Naming Views by Object Association   137
  Naming Views in Interface Builder   137
View Geometry   139
  Frames   140
  Rectangle Utility Functions   140
  Points and Sizes   141
  Transforms   142
  Coordinate Systems   142
Recipe: Working with View Frames   143
  Adjusting Sizes   144
  CGRects and Centers   146
  Other Geometric Elements   147
Recipe: Retrieving Transform Information   151
  Retrieving Transform Properties   151
  Testing for View Intersection   152
Display and Interaction Traits   157
UIView Animations   158
  Building Animations with Blocks   159
Recipe: Fading a View In and Out   159
Recipe: Swapping Views   161
Recipe: Flipping Views   162
Recipe: Using Core Animation Transitions   163
Recipe: Bouncing Views as They Appear   165
Recipe: Image View Animations   166
Summary   167

5  View Constraints   169
What Are Constraints?   169
Alignment Rectangles   170
  Declaring Alignment Rectangles   171
Constraint Attributes   171
  Constraint Math   172
The Laws of Constraints   173
Creating Constraints   175
  Basic Constraint Declarations   175
  Visual Format Constraints   176
  Variable Bindings   177
Format Strings   177
  Orientation   177
  View Names   179
  Connections   179
Predicates   183
  Metrics   183
  View-to-View Predicates   184
  Priorities   184
Format String Summary   184
Storing and Updating Constraints   186
Recipe: Comparing Constraints   187
Recipe: Describing Constraints   189
Recipe: Creating Fixed-Size Constrained Views   192
  Disabling Autosizing Constraints   192
  Starting within View Bounds   193
  Constraining Size   193
Recipe: Centering Views   196
Recipe: Setting Aspect Ratio   197
Aligning Views and Flexible Sizing   199
  Why You Cannot Distribute Views   199
Recipe: Responding to Orientation Changes   200
Constraint Macros   202
  Consistent Constraints   202
  Sufficient Constraints   203
  Macros   203
Debugging Your Constraints   205
Summary   207

6  Text Entry   209
Recipe: Dismissing a UITextField Keyboard   209
  Preventing Keyboard Dismissal   210
  Text Trait Properties   211
  Other Text Field Properties   212
Recipe: Dismissing Text Views with Custom Accessory Views   213
Recipe: Adjusting Views Around Keyboards   216
Recipe: Adjusting Views Around Accessory Views   220
  Testing for Hardware Keyboards   221
Recipe: Creating a Custom Input View   223
Recipe: Making Text-Input-Aware Views   227
Recipe: Adding Custom Input Views to Nontext Views   230
  Adding Input Clicks   231
Recipe: Building a Better Text Editor (Part I)   233
Recipe: Building a Better Text Editor (Part II)   236
  Enabling Attributed Text   236
  Controlling Attributes   236
  Other Responder Functionality   237
Recipe: Text-Entry Filtering   239
Recipe: Detecting Text Patterns   242
  Rolling Your Own Expressions   242
  Enumerating Regular Expressions   243
  Data Detectors   243
  Using Built-In Type Detectors   244
  Useful Websites   244
Recipe: Detecting Misspelling in a UITextView   246
Searching for Text Strings   247
Summary   248

7  Working with View Controllers   249
View Controllers   249
  The UIViewController Class   250
  Navigation Controllers   250
  Tab Bar Controllers   251
  Split View Controllers   251
  Page View Controller   251
  Popover Controllers   251
Developing with Navigation Controllers and Split Views   252
  Using Navigation Controllers and Stacks   253
  Pushing and Popping View Controllers   254
  Bar Buttons   254
Recipe: The Navigation Item Class   255
   Titles and Back Buttons   255
  Macros   256
Recipe: Modal Presentation   257
  Presenting a Custom Modal Information View   258
Recipe: Building Split View Controllers   261
Recipe: Creating Universal Split View/Navigation Apps   266
Recipe: Tab Bars   268
Remembering Tab State   272
Recipe: Page View Controllers   275
  Book Properties   276 
  Wrapping the Implemen  tation   277
  Exploring the Recipe   279
  Building a Presentation Index   279
Recipe: Scrubbing Pages in a Page View Controller   285
Recipe: Custom Containers   286
  Adding and Removing a Child View Controller   287
  Transitioning Between View Controllers   288
Recipe: Segues   292
  Segues, Interface Builder, and iOS 6   297
Summary   298

8  Common Controllers   299
Image Picker Controller   299
  Image Sources   299
  Presenting the Picker on iPhone and iPad 300
Recipe: Selecting Images   300
  How To: Adding Photos to the Simulator   301
  The Assets Library Framework   301
  Presenting a Picker   302
  Handling Delegate Callbacks   303
Recipe: Snapping Photos   306
  Setting Up the Picker   307
  Displaying Images   308
  Saving Images to the Photo Album   309
Recipe: Recording Video   310
  Creating the Video Recording Picker   311
  Saving the Video   311
Recipe: Playing Video with Media Player   313
Recipe: Editing Video   316
  AV Foundation and Core Media   316
Recipe: Picking and Editing Video   318
Recipe: E-Mailing Pictures   321
  Creating Message Contents   321
Recipe: Sending a Text Message   323
Recipe: Posting Social Updates   325
Recipe: Activity View Controller   328
  Creating and Presenting the Controller   328
  Adding Services   331
I  tems and Services   335
Recipe: The Quick Look Preview Controller   336
  Implementing Quick Look   337
Summary   340

9  Accessibility   341
Accessibility 101    341
  Accessibility in Interface Builder   342
Enabling Accessibility   343
Traits   344
Labels   345
Hints   346
Testing with the Simulator   347
Broadcasting Updates   348
Testing Accessibility on the iPhone   349
Summary   351

10  Creating and Managing Table Views   353
iOS Tables   353
Delegation   354
Creating Tables   355
  Table Styles   355
  Laying Out the View   355
Assigning a Data Source   356
Serving Cells   356
Registering Cell Classes   356
Dequeueing Cells   357
Assigning a Delegate   357
Recipe: Implementing a Basic Table   358
Data Source Methods   359
Responding to User Touches   359
Table View Cells   361
Selection Color   362
Adding in Custom Selection Traits   363
Recipe: Creating Checked Table Cells   363
Working with Disclosure Accessories   365
Recipe: Table Edits   367
Adding Undo Support   368
Supporting Undo   369
Displaying Remove Controls   369
Handling Delete Requests   369
Swiping Cells   370
Reordering Cells   370
Adding Cells    370
Recipe: Working with Sections   375
Building Sections    375
Counting Sections and Rows   376
Returning Cells   377
Creating Header Titles   378
Customizing Headers and Footers   379
Creating a Section Index   379
Handling Section Mismatches   380
Delegation with Sections   380
Recipe: Searching Through a Table   382
Creating a Search Display Controller   383
Registering Cells for the Search Display Controller   384
Building the Searchable Data Source Methods   384
Delegate Methods   385
Using a Search-Aware Index   386
Recipe: Adding Pull-to-Refresh to Your Table   388
Recipe: Adding Action Rows   391
Coding a Custom Group Table   394
  Creating Grouped Preferences Tables   395
Recipe: Building a Multiwheel Table   396
  Creating the UIPickerView   397
  Data Source and Delegate Methods   397
  Using Views with Pickers   397
Using the UIDatePicker   399
  Creating the Date Picker   400
Summary   401

11  Collection Views   403
Collection Views Versus Tables   403
  Practical Implementation Differences   405
Establishing Collection Views   405
  Controllers   405
  Views   406
  Data Sources and Delegates   406
Flow Layouts   407
  Scroll Direction   407
  Item Size and Line Spacing   407
  Header and Footer Sizing   409
  Insets   410
Recipe: Basic Collection View Flows   411
Recipe: Custom Cells   415
Recipe: Scrolling Horizontal Lists   416
Recipe: Introducing Interactive Layout Effects   420
Recipe: Scroll Snapping   422
Recipe: Creating a Circle Layout   423
  Creation and Deletion Animation   424
  Powering the Circle Layout   424
  The Layout   425
Recipe: Adding Gestures to Layout   429
Recipe: Creating a True Grid Layout   431
Recipe: Custom Item Menus   437
Summary   439

12  A Taste of Core Data   441
Introducing Core Data   441
Entities and Models   442
  Building a Model File   442
  Attributes and Relationships   443
  Building Object Classes   444
Creating Contexts   444
Adding Data   445
  Examining the Data File   446
Querying the Database   448
  Setting Up the Fetch Request   449
  Performing the Fetch   449
Removing Objects   450
Recipe: Using Core Data for a Table Data Source   451
  Index Path Access   451
  Section Key Path   451
  Section Groups   452
  Index Titles   452
  Table Readiness   452
Recipe: Search Tables and Core Data   455
Recipe: Adding Edits to Core Data Table Views   457
  Adding Undo/Redo Support   458
  Creating Undo Transactions   459
  Rethinking Edits   459
Recipe: A Core Data-Powered Collection View   464
Summary   469

13  Networking Basics   471
Recipe: Checking Your Network Status   471
Scanning for Connectivity Changes   474
Recipe: Synchronous Downloads   476
Recipe: Asynchronous Downloads   480
One-Call No-Feedback Asynchronous Downloads   486
Recipe: Using JSON Serialization   487
Recipe: Converting XML into Trees   489
  Trees    489
  Building a Parse Tree    490
Summary   492
Appendix Objective-C Literals   495
Numbers   495
Boxing   496
  Enums   496
Container Literals   497
Subscripting   498
Feature Tests   499
Index   501