How can I restart my block-based animation when the application comes to the foreground?

Question

I have the following block-based animation:

[UIView animateWithDuration:0.5f delay:0.0f 
                    options:UIViewAnimationOptionRepeat|UIViewAnimationOptionAutoreverse|UIViewAnimationOptionAllowUserInteraction|UIViewAnimationOptionCurveEaseInOut
                    animations:^{
                [view.layer setTransform:CATransform3DMakeScale(1.3f, 1.3f, 1.0f)];
                NSLog(@"animating");
                    }completion:^(BOOL finished){
                        NSLog(@"Completed");
                    }];

When the app returns from being in the background, the completion block is called, and my animations don't restart. I've tried to use the following delegate method to restart the animations:

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    /*
     Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
     */
    [[self viewController] animate];
    ......
}

but this hasn't worked to restore the animations.

Similarly, I've tried the approaches laid out in the answers to these questions:

but none of the suggestions there have worked for me. Is there another way to resume block-based UIView animations when an application has returned from the background?

score 5 · Accepted Answer · edited Nov 23 '17 at 01:33

A friend figured out the problem, needed to enableAnimations on the view when it returns from the background

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    /*
     Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
     */
    [UIView enableAnimations:YES];
    [[self viewController] animate];
    ......
}

then in the before the block animation need to removeAllAnimations and set layer.transform to Identity

hasStarted = YES;
    for(UIButton * button in goldenBreakOutButtons){
        for (UIView* view in button.subviews) {
            if (wasStarted) {
                [view.layer removeAllAnimations];
                view.layer.transform = CATransform3DIdentity;
            }
            if ([view isKindOfClass:[UIImageView class]]) {
                [UIView animateWithDuration:0.5f delay:0.0f 
                        options:UIViewAnimationOptionAutoreverse|UIViewAnimationOptionAllowUserInteraction|UIViewAnimationOptionCurveEaseInOut|UIViewAnimationOptionRepeat
                        animations:^ {
                            [view.layer setTransform:CATransform3DMakeScale(1.3f, 1.3f, 1.0f)];
                            NSLog(@"animating");
                        }
                        completion:^(BOOL finished){
                            if (finished) {
                                NSLog(@"Completed");
                            }

                        }];
            }
        }
    }

Where on earth did you find `[UIView enableAnimations:YES]`? I don't see that method anywhere :( — Nate, Aug 17 '12 at 10:35

score 2 · Answer 2 · edited Jun 20 '20 at 09:12

Please try to subscribe/unsubscribe in ViewController to
standart(UIApplicationWillEnterForegroundNotification) notification
from NSNotificationCenter:

 

    -(void) loadView
    {
    .....
    [[NSNotificationCenter defaultCenter] addObserver:self 
                                             selector:@selector(restartAnimation)    
                                                 name:UIApplicationWillEnterForegroundNotification 
                                               object:nil];      
    ....
    }
    
    - (void) viewDidUnload
    {
    ...
      [[NSNotificationCenter defaultCenter] removeObserver:self 
                                                      name:UIApplicationWillEnterForegroundNotification 
                                                    object:nil];
    ....
    }
    
    -(void) dealloc
    {
      [[NSNotificationCenter defaultCenter] removeObserver:self];
      [super dealloc];
    }
    
    - (void) restartAnimation
    {
        if(self.logoImageView)
        {
            [logoImageView.layer removeAllAnimations];
            
            CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
    
            animation.fromValue       = [NSNumber numberWithFloat:1.0];
            animation.toValue         = [NSNumber numberWithFloat:0.6];
            animation.duration        = 1.5f;
            animation.timingFunction  = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
            animation.autoreverses    = YES;
            animation.repeatCount     = HUGE_VALF;
            
            [[logoImageView layer] addAnimation:animation forKey:@"hidden"];
        }
    }

its already subscribed by default as UIApplicationWillEnterForegroundNotification is being called prior to application returning to the forground. — CStreel, Oct 20 '11 at 05:17

How can I restart my block-based animation when the application comes to the foreground?

2 Answers2

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