Pausing CALayer animation with an animation with a delay - ios

Question

I have a set of nested UIView animations (2 or 3 levels deep at a given time) that I would like to be able to pause and resume. Some of these animations use -animateWithDuration:animations:completion: while others use -animateWithDuration:delay:options:animations:completion: in order to delay execution of the animation block.
I read and implemented Technical Q&A QA1673 about pausing all animations in a layer tree, but I'm encountering an issue with the animations that use a delay parameter. I can pause and resume animations just fine, but when the animation resumes, any animation block that has a delay associated with it appears to have its delay extended by the amount of time that the layer tree was paused. So for example, if one of the blocks has a delay of 1 second, and the layer tree was paused for 3 seconds, the animation delays for 4 seconds after resuming. I'm guessing this has something to do with the beginTime property? Any help would be appreciated.
// Pause and Resume methods, right from the technical Q&A
- (void)pauseAnimationsOnLayer:(CALayer *)layer
{
CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
layer.speed = 0.0;
layer.timeOffset = pausedTime;
}
- (void)resumeAnimationsOnLayer:(CALayer *)layer
{
CFTimeInterval pausedTime = [layer timeOffset];
layer.speed = 1.0;
layer.timeOffset = 0.0;
layer.beginTime = 0;
CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
layer.beginTime = timeSincePause;
}
// Chained animations
- (void)animateNextPopup
{
[UIView animateWithDuration:kRFPVictorySequenceStatePopupDuration
animations:^{
[_currentStateImageView setHidden:NO];
[_currentStateImageView setTransform:CGAffineTransformIdentity];
}
completion:^(BOOL finished) {
[UIView animateWithDuration:kRFPVictorySequenceStateSlideOffDuration
delay:kRFPVictorySequenceStateVoteDelay
options:UIViewAnimationOptionCurveEaseInOut
animations:^{
if (winnerIsDem) {
[_currentStateImageView setFrame:CGRectMake(-_currentStateImageView.frame.size.width,
_currentStateImageView.frame.origin.y,
_currentStateImageView.frame.size.width,
_currentStateImageView.frame.size.height)];
}
else {
[_currentStateImageView setFrame:CGRectMake(1024,
_currentStateImageView.frame.origin.y,
_currentStateImageView.frame.size.width,
_currentStateImageView.frame.size.height)];
}
}
completion:^(BOOL finished) {
// Do some stuff
}
];
}
];
}

Answer 1

I found the solution to the problem! You have to reset the self.layer.beginTime value to zero in the completion block of your animations.
e.g.
[UIView animateWithDuration:element.duration
delay:element.delay
options:UIViewAnimationOptionCurveLinear
animations:^{
// Animate properties here!
}
} completion:^(BOOL finished){
// Reset BeginTime all the time
// So, in case a pause took place the delay values are valid again!
**self.layer.beginTime = 0.0f;**
}];
The rest of the pause / resume code stays exactly the same.
Best!

Answer 2

I suggest a different approach.
Animation blocks are easy to implement, but useful only if you do not need any control over your animation.
Otherwise, you should use a timer and create your own animation manually.
[NSTimer scheduledTimerWithTimeInterval:0.1
target:self
selector:#selector(timerFired)
userInfo:nil
repeats:YES];
- (void)timerFired
{
if (isPaused) {
// Do nothing
} else {
// Animate
}
}
- (IBAction)pauseTapped:(id)sender
{
if (isPaused) {
isPaused = NO;
} else {
isPaused = YES;
}
}
isPaused is a flag that control your animation state.