Pause and Resume UIViewAnimation when app goes to background - ios

Question

I am animating a view and I want to pause it and resume it.
Using an apple guide I created a CALayer Extension
extension CALayer {
func pause() {
var pauseTime = self.convertTime(CACurrentMediaTime(), fromLayer: nil)
self.speed = 0.0
self.timeOffset = pauseTime
}
func resume() {
var pausedTime = self.timeOffset
self.speed = 1.0
self.timeOffset = 0.0
self.beginTime = 0.0
var timeSincePause = self.convertTime(CACurrentMediaTime(), toLayer: nil) - pausedTime
self.beginTime = timeSincePause
}
}
This code is working perfectly except when that app goes to background. When I bring the App back to foreground animations is finished (even if the time is not pass) and it is not starting again when I click resume.
Ok. I tried animating CALayer but I have the same problem.
extension CALayer {
func animateY(newY:CGFloat,time:NSTimeInterval,completion:()->Void){
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
let animation = CABasicAnimation(keyPath: "position.y")
animation.fromValue = self.position.y
animation.toValue = newY
animation.duration = time
animation.delegate = self
animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
animation.removedOnCompletion = false // don't remove after finishing
self.position.y = newY
self.addAnimation(animation, forKey: "position.y")
CATransaction.flush()
}
}

Answer 1

I recommend using CABasicAnimation. Your resume/pause methods should be fine, since they are from this answer. You should try using Core Animation instead of UIViewAnimation and then the resume/pause will work.
Then you can register for the two notifications UIApplicationWillEnterForegroundNotification and UIApplicationDidEnterBackgroundNotification to have full control over the pause/resume actions.