[SOLVED] How to add animations to an already running animation based on the progress of the latter?

How to add animations to an already running animation based on the progress of the latter?

OBJECTIVE

Building a complex animation where some actions are triggered based on its progress.

QUESTION

Is it possible to check the progress of a UIViewPropertyAnimator and add animations when it reaches a given fraction complete that:

does not use UIView.animateKeyframes
does not require a user intervention

In other words, when the animator reaches a given fractionComplete, some animations are added to it.

ISSUES

The full animation comprises multiple animations of different objects (stored in an array). I need to both add animations at given times (based of % of completion) and add actions when some animations are completed.

Thanks for your kind help!

Solution

In some property, you can control delayFactor to add animation to replace previous target.

       let animView = UIView.init(frame: CGRect.init(x: 0, y: 0, width: 100, height: 200))
    animView.backgroundColor = UIColor.green

 animator =    UIViewPropertyAnimator.init(duration: 5.0, curve: UIView.AnimationCurve.easeInOut)

    view.addSubview(animView)
    animator.addCompletion { (position : UIViewAnimatingPosition) in
        if position == UIViewAnimatingPosition.end{
            animView.center  = CGPoint.init(x: 100, y: 300)
        }
    }
    animator.addAnimations({
        animView.center  = CGPoint.init(x: 600, y: 300)
    })
    animator.addAnimations({

        animView.center = CGPoint.init(x: 200, y: 200)
    }, delayFactor: 0.1)
    animator.addAnimations({

        animView.center = CGPoint.init(x: 300, y: 600)
    }, delayFactor: 0.5)
    animator.addAnimations({

        animView.center = CGPoint.init(x: 400, y: 400)
    }, delayFactor: 0.9)

        animator.startAnimation()