Friday, 24 October 2008

IPhone MoviePlayer Sample Code 4



Instance methods:
  • -(void)awakeFromNib;
  • -(void)dealloc;
  • -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;


  • #import "MyViewController.h"
Rotate the overlay 90 degrees clockwise then translate it to the centre of the screen. This will match the orientation the movie player uses, full-screen landscape mode.

Call super dealloc.

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
Similar to the MyImageView implementation. This creates a OverlayViewTouchNotification and fires it off.

IPhone MoviePlayer Sample Code 3



  • #import "MyViewController.h"
Instance variables:
  • mViewController
Instance methods:
  • -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;


-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
Receives a set with the touches and the event. Gets a UITouch from the set and check it's phase. If it's UITouchPhaseBegan, play the movie.

Thursday, 23 October 2008

IPhone MoviePlayer Sample Code 2



  • #import < MediaPlayer/MediaPlayer.h >
  • #import "MyOverlayView.h"
The line 'extern NSString * const OverlayViewTouchNotification' creates a global constant that will be used for touches to the overlay view. Any class importing MyViewController can access this variable.

Instance variables:
  • mMoviePlayer (MPMoviePlayerController)
  • mMovieURL (NSURL)
  • mOverlayView (MyOverlayView)
Instance methods:
  • -(NSURL *)movieURL;
  • -(void)initMoviePlayer;
  • -(IBAction)playMovie:(id)sender;
  • -(void)overlayViewTouches:(NSNotification *)notification;
  • -(IBAction)overlayViewButtonPress:(id)sender;


  • #import "MoviePlayerAppDelegate.h"
Initialise constant OverlayViewTouchNotification with the string 'overlayViewTouch'.

#pragma is a compiler directive. However the compiler ignores it if #pragma mark is used. #pragma mark helps with the organisation of your methods in the Xcode dropdown list.

'#pragma mark -' divvies up the methods by creating a spacer line while '#pragma mark Movie Player Routines' creates a bold label with the text 'Movie Player Routines'.

Movie Player Routines
- (void) moviePreloadDidFinish:(NSNotification*)notification
- (void) moviePlayBackDidFinish:(NSNotification*)notification
- (void) movieScalingModeDidChange:(NSNotification*)notification

These are events. When they are triggered is evident from the names. There is no code inside them.

  • Register MPMoviePlayerContentPreloadDidFinishNotification (named after the definition in MPMoviePlayerController.h) with NSNotificationCenter.
  • The movie player object, mMoviePlayer, is created by allocating MPMoviePlayerController and initialising it with movieURL.
  • Register MPMoviePlayerPlaybackDidFinishNotification and MPMoviePlayerScalingModeDidChangeNotification, giving mMoviePlayer as the notification sender.
  • Obtain the MoviePlayerAppDelegate object and use its instance variables to set mMoviePlayer.
  • Register OverlayViewTouchNotification.
  • Play mMoviePlayer.
  • Get the application windows in an array.
  • Get the movie player window.
  • Add mOverlayView as the subview of the movie player window.
View Controller Routines
-(NSURL *)movieURL
  • Check mMovieURL whether it's null or not.
  • Passing will return mMovieURL.
  • Failing will get the main bundle, look for 'Movie.m4v', check it and convert the path to NSURL before assigning it to movieURL.
-(BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation) interfaceOrientation
-(void)overlayViewTouches:(NSNotification *)notification

Trivial or empty methods.

Remove all registered notifications and release the movie player.

IPhone MoviePlayer Sample Code

Deconstructing the MoviePlayer app to see how the Media Player Framework ticks.

MoviePlayer has 4 classes:
  • MoviePlayerAppDelegate
  • MyImageView
  • MyOverlayView
  • MyViewController
A new IPhone application automatically creates 2 classes, with project name MPC, MPCAppDelegate and MPCViewController. Therefore, MyImageView and MyOverlayView are additions while MyViewController has been renamed.



There are 2 different ways of including a file/class:
  • #import "MyViewController.h"
  • @class MyViewController;
The interface lists 3 instance variables of type NSInteger aside from the default UIWindow and ViewController:
  • backgroundColor
  • controlMode
  • scalingMode
The @property declares the accessor methods for the 5 variables. It has attributes which modify the accessors.

Example: @property (nonatomic, retain) UIWindow *window;

nonatomic means the accessor returns the value directly, the default is to lock, get value, unlock which is meant for multithreaded environments.

assign, retain or copy must be explicitly set if garbage collection is not used. assign is the default and means the setter uses a simple assignment. retain keeps the object variable in-memory and cannot be deallocated without your permission. copy means that a copy of the object should be used for assignment and the previous one is sent a release message.

3 instance methods:
  • -(void)setUserSettingsDefaults;
  • -(void)applicationDidFinishLaunching:(UIApplication *)application;
  • -(void)dealloc;


3 NSString keys:
  • kScalingModeKey = @"scalingMode"
  • kControlModeKey = @"controlMode"
  • kBackgroundColorKey = @"backgroundColor"
@synthesize generates the accessors according to the attributes listed. If implemented manually, the code must follow what has been specified in the @property. @synthesize will only generate accessors that don't exist so if a variable has a setter already, then only a getter will be generated.

Sets up a test calling NSUserDefaults to see if there's a match. Passing will set the scalingMode, controlMode and backgroundColor variables. Failing will create the values based on the settings bundle info and then set the variables:
  • Get the path to the main bundle of the project.
  • Append Settings.bundle to the path using stringByAppendingPathComponent, which takes care of adding separators.
  • Append Root.plist to the path, same as before.
  • Create a dictionary using dictionaryWithContentsOfFile, giving the path to Root.plist.
  • Create the prefSpecifierArray array from the dictionary using the key, PreferenceSpecifiers, which is a tag in Root.plist.
    • Root.plist is an XML file with dict, array and key tags. May be an easy way to read XML.
  • Declare 3 NSNumber variables and a dictionary, prefItem.
  • Loop prefSpecifierArray with the current value going into prefItem.
    • Set keyValueStr with the dictionary using the key, 'Key'.
    • Set defaultValue with the dictionary using the key, 'DefaultValue'.
    • Check if keyValueStr is equal to any NSStrings specified above.
    • Set the numbers with defaultValue if any is correct.
  • Create a dictionary containing the default values and their keys.
  • Register the dictionary with NSUserDefaults using registerDefaults.
  • Updates and writes to the persistent domains using synchronize.
-(void)applicationDidFinishLaunching:(UIApplication *)application
Add the ViewController's view as a subview of the UIWindow. Call self with setUserSettingsDefaults to get the default movie player settings. Lastly, call the ViewController with initMoviePlayer to create a movie player object.

Release the UIWindow and the ViewController. Call the super's dealloc method.

Tuesday, 21 October 2008

Objective-C Classes

Objective-C (Obj-C) is C with Object Oriented Programming tacked on. The object syntax takes some time to get used to, as it is decidedly different from the normal C++/Java syntax.

There are two parts for an object in Obj-C, which are the interface and the implementation. The parts should be stored separately, the interface in a header file (*.h) and the implementation is a *.m file.

The interface stores the instance variables and the prototypes for the class and instance methods. The implementation defines those methods.

Sample code:

*** CounterController.h ***
#import < Cocoa/Cocoa.h >
@interface CounterController : NSObject {
IBOutlet id display_update;
int count;
- (IBAction)minus_button_pushed:(id)sender;
- (IBAction)p10_button_pushed:(id)sender;
- (IBAction)plus_button_pushed:(id)sender;

*** CounterController.m ***
#import "CounterController.h"
@implementation CounterController
- (IBAction)minus_button_pushed:(id)sender {
[display_update setIntValue:count];
- (IBAction)p10_button_pushed:(id)sender {
[display_update setIntValue:count];
- (IBAction)plus_button_pushed:(id)sender {
[display_update setIntValue:count];

Things of note:
  • Obj-C uses import instead of include.
  • The class CounterController is a subclass of NSObject.
  • Inside the brackets are the instance variables display_update and count.
  • The IBOutlet before display_update means the display_update is an output on the GUI display in the Interface Builder.
  • id is a general type, meaning any object.
  • (IBAction)minus_button_pushed:(id)sender translates to IBAction minus_button_pushed(id sender).
  • The - before the methods classify them as instance methods, + for class methods.
  • The brackets [] indicate messaging, [display_update setIntValue:count] translates to display_update.setIntValue(count).