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

Question

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!

Answer 1

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()