Animating CALayer's shadowPath property

Question

I am aware that a CALayer\'s shadowPath is only animatable using explicit animations, however I still cannot get this to work. I suspect that I am not passing the toVa

Answer 1

I've met same problem for shadow animation and find solution for persisting shadow after end of animation. You need to set final path to your shadow layer before you start animation. Reverting to initial shadow happens because CoreAnimation does not update properties of original layer, it creates copy of this layer and display animation on this copy (check Neko1kat answer for more details). After animation ended system removes this animated layer and return original layer, that has not updated path and your old shadow appears. Try this code:

    let shadowAnimation = CABasicAnimation(keyPath: "shadowPath")
    shadowAnimation.fromValue = currentShadowPath
    shadowAnimation.toValue = newShadowPath
    shadowAnimation.duration = 3.0

    shadowLayer.shadowPath = newShadowPath
    shadowLayer.add(shadowAnimation, forKey: "shadowAnimation")

Answer 2

Firstly, you did not set the animation's fromValue.

Secondly, you're correct: toValue accepts a CGPathRef, except it needs to be cast to id. Do something like this:

theAnimation.toValue = (id)[UIBezierPath bezierPathWithRect:newRect].CGPath;

You'll also need to set the shadowPath property of the layer explicitly if you want the change to remain after animation.

Answer 3

let cornerRadious = 10.0
        //
        let shadowPathFrom = UIBezierPath(roundedRect: rect1, cornerRadius: cornerRadious)
        let shadowPathTo = UIBezierPath(roundedRect: rect2, cornerRadius: cornerRadious)
        //
        layer.masksToBounds = false
        layer.shadowColor = UIColor.yellowColor().CGColor
        layer.shadowOpacity = 0.6
        //
        let shadowAnimation = CABasicAnimation(keyPath: "shadowPath")
        shadowAnimation.fromValue = shadowPathFrom.CGPath
        shadowAnimation.toValue = shadowPathTo.CGPath
        shadowAnimation.duration = 0.4
        shadowAnimation.autoreverses = true
        shadowAnimation.removedOnCompletion = true
        shadowAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
        layer.addAnimation(shadowAnimation, forKey: "shadowAnimation")