How to animate layer shadowOpacity?

Question

I have a view on which I\'ve set the layerOpacity to 1.

    theView.layer.shadowOpacity = 1.0;

This looks fine when the view is farther down th

Answer 1

Here's a material design like take on some of the above with animations It's also available here as framework through Carthage https://github.com/sevenapps/SVNMaterialButton

public init(frame: CGRect, color: UIColor) {
    super.init(frame: frame)
    self.backgroundColor = color
    self.layer.masksToBounds = false
    self.layer.borderWidth = 1.0
    self.layer.shadowColor = UIColor.black.cgColor
    self.layer.shadowOpacity = 0.8
    self.layer.shadowRadius = 8
    self.layer.shadowOffset = CGSize(width: 8.0, height: 8.0)
}

required public init?(coder aDecoder: NSCoder) {
    fatalError("This class is not set up to be instaciated with coder use init(frame) instead")
}

public override func layoutSubviews() {
    super.layoutSubviews()
    self.layer.cornerRadius = self.frame.height / 4
}

public override func touchesBegan(_ touches: Set, with event: UIEvent?) {
    self.animate(to: 0.5, and: CGSize(width: 5.0, height: 5.0), with: 0.5)
    super.touchesBegan(touches, with: event)
}

public override func touchesEnded(_ touches: Set, with event: UIEvent?) {
    self.animate(to: 0.8, and: CGSize(width: 8.0, height: 8.0), with: 0.5)
    super.touchesBegan(touches, with: event)
}

private func animate(to opacity: Double, and offset: CGSize, with duration: Double){
    CATransaction.begin()
    let opacityAnimation = CABasicAnimation(keyPath: "shadowOpacity")
    opacityAnimation.toValue = opacity
    opacityAnimation.duration = duration
    opacityAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
    opacityAnimation.fillMode = kCAFillModeBoth
    opacityAnimation.isRemovedOnCompletion = false

    let offsetAnimation = CABasicAnimation(keyPath: "shadowOffset")
    offsetAnimation.toValue = offset
    offsetAnimation.duration = duration
    offsetAnimation.timingFunction = opacityAnimation.timingFunction
    offsetAnimation.fillMode = opacityAnimation.fillMode
    offsetAnimation.isRemovedOnCompletion = false

    self.layer.add(offsetAnimation, forKey: offsetAnimation.keyPath!)
    self.layer.add(opacityAnimation, forKey: opacityAnimation.keyPath!)
    CATransaction.commit()
}