Resuming UIView Animations on App Re-Entry?

Question

I have 2 UIImageView's in the main view controller of my app. They are always animating via UIView animations. What I want to achieve is when the user clicks the home button, pause the UIView animations, and when the user comes back to the app, resume the animations.

So to pause I call a method from my app delegate to my ViewController to pause in the applicationWillResignActive call.

And to resume I call a method also from the app delegate to my ViewController to resume in the applicationDidBecomeActive method.

This is the code I use to either pause or resume my animations:

-(void)pauseLayer:(CALayer*)layer {
    CFTimeInterval paused_time = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
    layer.speed = 0.0;
    layer.timeOffset = paused_time;
}

-(void)resumeLayer:(CALayer*)layer {
    CFTimeInterval paused_time = [layer timeOffset];
    layer.speed = 1.0f;
    layer.timeOffset = 0.0f;
    layer.beginTime = 0.0f;
    CFTimeInterval time_since_pause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - paused_time;
    layer.beginTime = time_since_pause;
}

- (void)pause:(BOOL)theBool {
    if (theBool) {
        [self pauseLayer:self.myImageView.layer];
        [self pauseLayer:self.myImageViewleft.layer];
    } else {
        [self resumeLayer:self.myImageView.layer];
        [self resumeLayer:self.myImageViewleft.layer];
    }
}

So I NSLogged everything and the methods get called accordingly however when I go to resume the animations, the image views don't resume from where they left off and are most likely at the position I placed them in the XIB (off the screen).

So when I re-enter my app, does my XIB get reloaded or something? There is absolutely nothing that should be changing the position of those UIImageView's, thats why I am really confused why this is happening.

Edit: I have also tried creating my images programmatically, no luck same issue. The pausing and resuming works successfully if I do it via buttons in my app while its running, it seems the problem is with the application delegate methods or something.

If anyone sees what's wrong, please let me know!

have you tried creating your `UIImageView`s programmatically ? — KDaker, Aug 25 '12 at 05:34
Yep, no luck either. Same problem. If I just do this via buttons in my app it works fine, so it has something to do with the delegate methods. Its really strange. — SimplyKiwi, Aug 26 '12 at 02:16
have you tried using `application:didEnterBackground` and `willEnterForeground` instead of resignActive and becomeActive? — KDaker, Aug 26 '12 at 02:23

SimplyKiwi · Accepted Answer · 2012-08-28T01:59:11.700

2

I found this to be really complicated and tricky so for now I will just use Cocos2D instead and make use of CCDirector's pause feature.

Edit: Just tried CCDirector's pause feature and it works perfectly. Definitely go this route!!!

edited Aug 28 '12 at 01:59

answered Aug 27 '12 at 23:59

SimplyKiwi

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Resuming UIView Animations on App Re-Entry?

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