Start/stop image view rotation animations - ios

Question

I have a start/stop button and an image view which I want to rotate.
When I press the button I want the to start rotating and when I press the button again the image should stop rotating. I am currently using an UIView animation, but I haven't figured out a way to stop the view animations.
I want the image to rotate, but when the animation stops the image shouldn't go back to the starting position, but instead continue the animation.
var isTapped = true
#IBAction func startStopButtonTapped(_ sender: Any) {
ruotate()
isTapped = !isTapped
}
func ruotate() {
if isTapped {
UIView.animate(withDuration: 5, delay: 0, options: .repeat, animations: { () -> Void in
self.imageWood.transform = self.imageWood.transform.rotated(by: CGFloat(M_PI_2))
}, completion: { finished in
ruotate()
})
} }
It is my code, but it doesn't work like I aspect.

Answer 1

Swift 3.x
Start Animation
let rotationAnimation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
rotationAnimation.toValue = NSNumber(value: .pi * 2.0)
rotationAnimation.duration = 0.5;
rotationAnimation.isCumulative = true;
rotationAnimation.repeatCount = .infinity;
self.imageWood?.layer.add(rotationAnimation, forKey: "rotationAnimation")
Stop animation
self.imageWood?.layer.removeAnimation(forKey: "rotationAnimation")
Swift 2.x
Start Animation
let rotationAnimation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
rotationAnimation.toValue = NSNumber(double: M_PI * 2.0)
rotationAnimation.duration = 1;
rotationAnimation.cumulative = true;
rotationAnimation.repeatCount = .infinity;
self.imageWood?.layer.addAnimation(rotationAnimation, forKey: "rotationAnimation")
Stop animation
self.imageWood?.layer.removeAnimation(forKey: "rotationAnimation")

Answer 2

If you use UIView Animation the OS still creates one or more CAAnimation objects. Thus, to stop a UIView animation you can still use:
myView.layer.removeAllAnimations()
Or if you create the animation using a CAAnimation on a layer:
myLayer.removeAllAnimations()
In either case, you can capture the current state of the animation and set that as the final state before removing the animation. If you're doing an animation on a view's transform, like in this question, that code might look like this:
func stopAnimationForView(_ myView: UIView) {
//Get the current transform from the layer's presentation layer
//(The presentation layer has the state of the "in flight" animation)
let transform = myView.layer.presentationLayer.transform
//Set the layer's transform to the current state of the transform
//from the "in-flight" animation
myView.layer.transform = transform
//Now remove the animation
//and the view's layer will keep the current rotation
myView.layer.removeAllAnimations()
}
If you're animating a property other than the transform you'd need to change the code above.

Answer 3

using your existing code you can achieve it the following way
var isTapped = true
#IBAction func startStopButtonTapped(_ sender: Any) {
ruotate()
isTapped = !isTapped
}
func ruotate() {
if isTapped {
let rotationAnimation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
rotationAnimation.toValue = NSNumber(value: Double.pi * 2.0)
rotationAnimation.duration = 1;
rotationAnimation.isCumulative = true;
rotationAnimation.repeatCount = HUGE;
self.imageWood?.layer.add(rotationAnimation, forKey: "rotationAnimation")
}else{
self.imageWood?.layer.removeAnimation(forKey: "rotationAnimation")
}
}

Answer 4

Apple added a new class, UIViewPropertyAnimator, to iOS 10. A UIViewPropertyAnimator allows you to easily create UIView-based animations that can be paused, reversed, and scrubbed back and forth.
If you refactor your code to use a A UIViewPropertyAnimator you should be able to pause and resume your animation.
I have a sample project on Github that demonstrates using a UIViewPropertyAnimator. I suggest taking a look at that.

Answer 5

Your code make the image rotate for 2PI angle, but if you click on the button while the rotation is not ended, the animation will finish before stop, that's why it comes to the initial position.
You should use CABasicAnimation to use a rotation that you can stop at anytime keeping the last position.