Is there a way to pause a CABasicAnimation?

Question

I have a basic spinning animation of the iPhone. Is there any way that I can "pause" the animation so that the position of the view will be maintained? I guess one way of doing this would be to cause the animation to "complete" instead of calling "remove" on it, how would I do that?

CABasicAnimation* rotationAnimation;
rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
rotationAnimation.toValue = [NSNumber numberWithFloat: M_PI * 2];
rotationAnimation.duration = 100;
rotationAnimation.cumulative = YES;
rotationAnimation.repeatCount = HUGE_VALF;
rotationAnimation.removedOnCompletion = NO;
rotationAnimation.fillMode = kCAFillModeForwards;
[myView.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];

Answer 1

You can use a timer or handle the animation delegate method:

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag

Here is my code:

// ...
[self startAnimation];
// ...

- (void)startAnimation {
CABasicAnimation* rotationAnimation;
rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
rotationAnimation.fromValue = [NSNumber numberWithFloat:0];
rotationAnimation.toValue = [NSNumber numberWithFloat: M_2_PI];
rotationAnimation.duration = 1.0;
rotationAnimation.cumulative = YES;
// rotationAnimation.repeatCount = 0; // <- if repeatCount set to infinite, we'll not receive the animationDidStop notification when the animation is repeating
rotationAnimation.removedOnCompletion = NO;
rotationAnimation.fillMode = kCAFillModeForwards;
rotationAnimation.delegate = self; // <- hanlde the animationDidStop method
[myView.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];

}

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag {
if (shouldContinueAnimation) // <- set a flag to start/stop the animation
    [self startAnimation];
}

Hope it can help you.

Answer 2

Recently appeared Apple's technical note QA1673 describes how to pause/resume layer's animation.

Pause and resume animations listing is below:

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

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

Edit: iOS 10 introduced new API - UIViewPropertyAnimator that allows to handle animations more interactively, for example it makes easy to pause and resume animation or 'seek' it to some particular progress value.

Answer 3

Answer For Swift 3:

Credits @Vladimir

Code:

 func pauseAnimation(){
  var pausedTime = layer.convertTime(CACurrentMediaTime(), fromLayer: nil)
  layer.speed = 0.0
  layer.timeOffset = pausedTime
}

func resumeAnimation(){
  var pausedTime = layer.timeOffset
  layer.speed = 1.0
  layer.timeOffset = 0.0
  layer.beginTime = 0.0
  let timeSincePause = layer.convertTime(CACurrentMediaTime(), fromLayer: nil) - pausedTime
  layer.beginTime = timeSincePause
}

Answer 4

Simplest One

self.viewBall.layer.position = self.viewBall.layer.presentationLayer().position

Answer 5

Set the current state of your view's layer to match the state of the presentationLayer, then remove the animation:

CALayer *pLayer = [myView.layer presentationLayer];
myView.layer.transform = pLayer.transform;
[myView.layer removeAnimationForKey:@"rotationAnimation"];