run animation every time app is opened

I have an animation in viewDidLoad that runs the first time the app is launched. if you exit the app, then launch it again the animation doesn't play.

h开发者_如何学JAVAow would I go about making the animation play each and every time the app is opened,

thanks for any help

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In iOS 4, pressing the home button doesn't terminate the app, it suspends it. When the app is made active again, a UIApplicationDidBecomeActiveNotification is posted. Register for that notification and initiate the animation in your handler.

Edit: Added code below.

Here's one way to do it: Have your view controller become an observer of UIApplicationDidBecomeActiveNotification in its viewWillAppear: method.

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(performAnimation:) name:UIApplicationDidBecomeActiveNotification object:nil];
}

Unregister for the notification in your view controller's viewDidDisappear: method.

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidBecomeActiveNotification object:nil];
}

Finally, put your animation code in the selector specified when registering to receive the notification.

- (void)performAnimation:(NSNotification *)aNotification {
    // Animation code.
}

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http://developer.apple.com/library/ios/#documentation/uikit/reference/UIApplicationDelegate_Protocol/Reference/Reference.html

Put the animation in a method like

applicationDidBecomeActive:

of UIApplicationDelegate

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Very likely your app isn't quitting and reloading. By default, on iOS 4 apps continue to run when the user 'exits' the app, and continue where they left off when 'restarted'.

Take a look at applicationDidBecomeActive in your app delegate. You could kick off your animation from there when the app is deactivated.

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How about set a flag in your application delegate to control this behavior:

Set it to YES when the app enters the foreground or became active (applicationWillEnterForeground:, applicationDidBecomeActive:)

Check if this flag is NO in -viewWillAppear in your view controller:

MyAppDelegate *delegate = [[UIApplication sharedApplication] delegate];
if(!delegate.animationPlayed) {
   //perform animation here...
   delegate.animationPlayed = YES;
}