IPhoneDev

From M-Gate Labs Wiki

This page is still under development, I have been working with the iPhone SDK and finally go the Interface builder to work, more updates will follow.

--SlashAndBurn 19:16, 30 June 2008 (MST)

Contents 1 Objective C 1.1 File Types 1.2 Include 1.3 Strings 1.4 Classes 1.4.1 interface 1.4.2 implementation 1.5 variables 1.5.1 strong typed 1.5.2 weak typed 1.6 methods 1.6.1 instance 1.6.2 class 1.6.3 declaration 1.6.4 calling 1.7 Properties 1.8 Protocols & Delegates 1.8.1 protocols 1.8.2 delegates 1.8.3 declaration 2 Application 2.1 problems 2.1.1 entry point 2.2 application delegate 2.3 application window 2.3.1 At launch time 2.3.2 drawing 2.3.3 touching 2.3.4 accelerometer

Objective C

File Types

• .h
  • Header files.
  • Header files contain class, type, function, and constant declarations.
• .m
  • Source files.
  • This is the typical extension used for source files and can contain both Objective-C and C code.
• .mm
  • Source files.
  • A source file with this extension can contain C++ code in addition to Objective-C and C code. This extension should be used only if you actually refer to C++ classes or features from your Objective-C code.

Include

• #include
  • Same as C, C++ #include statement
• #import
  • Like #include, but will not reference the same file more then once

Strings

• Shortcut
  • Append a @ to the front of a double quoted string

  NSString*  myString = @"My String\n";
  NSString*  anotherString = [NSString stringWithFormat:@"%d %s", 1, @"String"]; 
  // Create an Objective-C string from a C string
  NSString*  fromCString = [NSString stringWithCString:"A C string" encoding:NSASCIIStringEncoding];

Classes

interface

  @interface MyClass : NSObject
  {
     int  count;
     id   data;
     NSString* name;
  }
  - (id)initWithString:(NSString*)aName;
  + (MyClass*)createMyClassWithString:(NSString*)aName;
  @end

implementation

  @implementation MyClass
  - (id)initWithString:(NSString *) aName
  {
     if (self = [super init])
     {
        count count = 0;
        data = nil;
        name = [aName copy];
        return self;
      }
  }
  + (MyClass *)createMyClassWithString: (NSString *) aName
  {
      return [[[self alloc] initWithString:aName] autorelease];
  }
  @end

variables

strong typed

  MyClass* myObject1;

• Object types should be declared as a pointer

weak typed

  id myObject2;

• id type is a pointer type

methods

instance

• Starts with a -
• is a method whose execution is scoped to a particular instance of the class
• before you call an instance method, you must first create an instance of the class

class

• starts with a +
• do not require you to create an instance
• basically a static method

declaration

- (void)insertObject:(id)anObject asIndex:(NSUInteger)index

• -
  • Method type indentifier
• (void)
  • Return Type
• insertObject
  • Method Signature
• (id)
  • Parameter Type
• anObject
  • Parameter Names
• atIndex
  • Method Signature

• (NSUInteger)
  • Parameter Type
• index
  • Parameter Names

calling

  [myArray insertObject:anObj atIndex:0]

• [
• myArray
  • Referenced Object
• insertObject
  • signature

• anObj
  • value
• atIndex
  • signature

• 0
  • value
• ]

Properties

• Properties are a convenience notation used to replace accessor method declarations
• shorthand for defining methods that access existing instance variables
• reduce the amount of redundant code you have to write

  @property BOOL flag;
  @property (copy) NSString* nameObject;  // Copy the object during assignment.
  @property (readonly) UIView* rootView;  // Create only a getter method.

• Another benefit of properties is that you can use dot syntax when accessing them in your code, as shown in the following example:

  myObject.flag = YES;
  //[myObject setFlag:YES];
  CGRect   viewFrame = myObject.rootView.frame;
  //CGRect   viewFrame = [[myObject rootView] frame];

Protocols & Delegates

protocols

• protocol declares methods that can be implemented by any class
• define an interface that other objects are responsible for implementing

delegates

• a delegate object is an object that acts on behalf of, or in coordination with, another object

declaration

  @protocol MyProtocol
  - (void)myProtocolMethod;
  @end

Application

problems

• iPhone OS does not support memory management using the garbage collection feature that is in Mac OS X v10.5 and later.

entry point

  int main(int argc, char *argv[])
  {
     //creates the application's top-level autorelease pool, whose job is to reclaim the memory for Objective-C objects that are freed using their autorelease method
     NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
     //calls the UIApplicationMain function to create the MoveMe application's key objects, initialize those objects, and start the event-processing loop. The application does not return from this function until it quits
     int retVal = UIApplicationMain(argc, argv, nil, nil);
     [pool release];
     return retVal;
  }

application delegate

• use Interface Builder to designate the class as the application delegate
• application delegate object works in tandem with the standard UIApplication object to respond to changing conditions in the application
• application object does most of the heavy lifting, but the delegate is responsible for several key behaviors
  • Setting up the application's window and initial user interface
  • Performing any additional initialization tasks needed for your custom data engine
  • Opening content associated with the application's custom URL schemes
  • Responding to changes in the orientation of the device
  • Handling low-memory warnings
  • Handling system requests to quit the application
• at launch time, the most immediate concern for the delegate object is to set up and present the application window to the user
• when the application quits, the delegate needs to perform an orderly shutdown of the application and save any state information needed for the next launch cycle

application window

• your application is the only thing running after it is launched
• your application should never need more than one window—an instance of the UIWindow class
  • In situations where you need to change your user interface, you change the views displayed by your window
• windows provide the drawing surface for your user interface, but view objects provide the actual content
• a view object is an instance of the UIView class that draws some content and responds to interactions with that content

At launch time

• The window is unarchived from the MainWindow.xib nib file
• When the application reaches a state where it is launched and ready to start processing events, the UIApplication object sends the delegate an applicationDidFinishLaunching: message
• the initWithCoder: method called when the MoveMeView object is unarchived from its nib file

  - (void)applicationDidFinishLaunching:(UIApplication *)application
  {
     // Set up the view controller
     UIViewController *aViewController = [[UIViewController alloc]
              initWithNibName:@"MoveMeView" bundle:[NSBundle mainBundle]];
     self.viewController = aViewController;
     [aViewController release];

     // Add the view controller's view as a subview of the window
     UIView *controllersView = [viewController view];
     [window addSubview:controllersView];
     [window makeKeyAndVisible];
  }

  - (void)setUpPlacardView
  {		
     // Create the placard view -- it calculates its own frame based on its image
     PlacardView *aPlacardView = [[PlacardView alloc] init];
     self.placardView = aPlacardView;
     [aPlacardView release];
     placardView.center = self.center;
     [self addSubview:placardView];
  }

drawing

• custom rendering can be achieved by overloading the drawRect: method

  - (void)drawRect:(CGRect)rect
  {
      // Draw the placard at 0, 0
      [placardImage drawAtPoint:(CGPointMake(0.0, 0.0))];
   
      /*
       Draw the current display string.
       This could be done using a UILabel, but this serves to illustrate
       the UIKit extensions to NSString. The text is drawn center of the
       view twice - first slightly offset in black, then in white -- to give
       an embossed appearance. The size of the font and text are calculated
       in setupNextDisplayString.
       */
   
      // Find point at which to draw the string so it will be in the center of the view
      CGFloat x = self.bounds.size.width/2 - textSize.width/2;
      CGFloat y = self.bounds.size.height/2 - textSize.height/2;
      CGPoint point;
   
      // Get the font of the appropriate size
      UIFont *font = [UIFont systemFontOfSize:fontSize];
   
      [[UIColor blackColor] set];
      point = CGPointMake(x, y + 0.5);
      [currentDisplayString drawAtPoint:point
                  forWidth:(self.bounds.size.width-STRING_INDENT)
                  withFont:font
                  fontSize:fontSize
                  lineBreakMode:UILineBreakModeMiddleTruncation
                  baselineAdjustment:UIBaselineAdjustmentAlignBaselines];
   
      [[UIColor whiteColor] set];
      point = CGPointMake(x, y);
  			
      [currentDisplayString drawAtPoint:point
                  forWidth:(self.bounds.size.width-STRING_INDENT)
                  withFont:font
                  fontSize:fontSize
                  lineBreakMode:UILineBreakModeMiddleTruncation
  }

touching

• UIView disables multitouch by default
• you can reenable multi-touch support using the setMultipleTouchEnabled: method of the UIView class

• a class detects taps by overriding the following methods of UIResponder:

  - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
  - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
  - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;

  - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
  {
      // We only support single touches, so anyObject
      // retrieves just that touch from touches
      UITouch *touch = [touches anyObject];
   
      // Only move the placard view if the touch was in the placard view
      if ([touch view] != placardView)
      {
          // In case of a double tap outside the placard view,
          // update the placard's display string
          if ([touch tapCount] == 2)
          {
              [placardView setupNextDisplayString];
          }
          return;
      }
      // Animate the first touch
      CGPoint touchPoint = [touch locationInView:self];
      [self animateFirstTouchAtPoint:touchPoint];
  }

  - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
  {
      UITouch *touch = [touches anyObject];
   
      // If the touch was in the placardView, move the placardView
      // to its location
      if ([touch view] == placardView)
      {
          CGPoint location = [touch locationInView:self];
          placardView.center = location;
          return;
      }
  }

  - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
  {
      UITouch *touch = [touches anyObject];
   
      // If the touch was in the placardView, bounce it back to the center
      if ([touch view] == placardView)
      {
          // Disable user interaction so subsequent touches
          // don't interfere with animation
          self.userInteractionEnabled = NO;
          [self animatePlacardViewToCenter];
          return;
      }
  }

accelerometer

• use the UIAccelerometer to get position information