swift - chaining UIView animation

Question

I'd like to animate my UIImageView with these steps:

1. scale 2 times
2. scaled image movement

So I'm trying like this:

UIView.animate(withDuration: 0.5, animations: {
   self.imageView.transform = CGAffineTransform(scaleX: 2, y: 2)                        
}) { _ in                        
   UIView.animate(withDuration: 1.0, animations: {
        self.imageView.transform = CGAffineTransform(translationX: -50, y: -50)
                        
   }) { _ in

        //other steps
   }
 }

But the result is that before moving imageView got back to previous size and then moving. How to move scaled view?

also I've tried to change layer's anchorPoint inside the animate block with no success

And maybe there is more simple way to achieve my goal: ability to zoom out image, then focus at 3 custom points, then zoom in to the initial size.

Answer 1

One approach is to put the start of an animation in the completion handler of the prior animation:

UIView.animate(withDuration: 1) { 
    // animation 1
} completion: { _ in
    UIView.animate(withDuration: 2) { 
        // animation 2
    } completion: {  _ in 
        UIView.animate(withDuration: 1) { 
            // animation 3
        } completion: {  _ in 
            // etc
        }
    }
}

If you want to avoid a tower of nested animations (each in the completion handler of the prior one), you can use a keyframe animation, e.g. this is a five second animation with three separate keyframes, each with a duration of one third of the total, and whose start time is set accordingly:

UIView.animateKeyframes(withDuration: 5, delay: 0) { 
    UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 1 / 3) {
        // animation 1
    }
    
    UIView.addKeyframe(withRelativeStartTime: 1 / 3, relativeDuration: 1 / 3) {
        // animation 2
    }
    
    UIView.addKeyframe(withRelativeStartTime: 2 / 3, relativeDuration: 1 / 3) {
        // animation 3
    }
}

The above is for Swift 5.3 and later. For earlier versions, see previous revision of this answer.