Animate UIView's Layer with constrains (Auto Layout Animations) - ios

Question

I am working on project where I need to animate height of view which consist of shadow, gradient and rounded corners (not all corners).
So I have used layerClass property of view.
Below is simple example demonstration.
Problem is that, when I change height of view by modifying its constraint, it was resulting in immediate animation of layer class, which is kind of awkward.
Below is my sample code
import UIKit
class CustomView: UIView{
var isAnimating: Bool = false
override init(frame: CGRect) {
super.init(frame: frame)
self.setupView()
}
func setupView(){
self.layoutMargins = UIEdgeInsets(top: 20, left: 20, bottom: 20, right: 20)
guard let layer = self.layer as? CAShapeLayer else { return }
layer.fillColor = UIColor.green.cgColor
layer.shadowColor = UIColor.black.cgColor
layer.shadowOffset = CGSize(width: 0.0, height: 2.0)
layer.shadowOpacity = 0.6
layer.shadowRadius = 5
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override class var layerClass: AnyClass {
return CAShapeLayer.self
}
override func layoutSubviews() {
super.layoutSubviews()
// While animating `myView` height, this method gets called
// So new bounds for layer will be calculated and set immediately
// This result in not proper animation
// check by making below condition always true
if !self.isAnimating{ //if true{
guard let layer = self.layer as? CAShapeLayer else { return }
layer.path = UIBezierPath(roundedRect: bounds, cornerRadius: 10).cgPath
layer.shadowPath = layer.path
}
}
}
class TestViewController : UIViewController {
// height constraint for animating height
var heightConstarint: NSLayoutConstraint?
var heightToAnimate: CGFloat = 200
lazy var myView: CustomView = {
let view = CustomView()
view.translatesAutoresizingMaskIntoConstraints = false
view.backgroundColor = .clear
return view
}()
lazy var mySubview: UIView = {
let view = UIView()
view.translatesAutoresizingMaskIntoConstraints = false
view.backgroundColor = .yellow
return view
}()
lazy var button: UIButton = {
let button = UIButton(frame: .zero)
button.translatesAutoresizingMaskIntoConstraints = false
button.setTitle("Animate", for: .normal)
button.setTitleColor(.black, for: .normal)
button.addTarget(self, action: #selector(self.animateView(_:)), for: .touchUpInside)
return button
}()
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = .white
self.view.addSubview(self.myView)
self.myView.addSubview(self.mySubview)
self.view.addSubview(self.button)
self.myView.leadingAnchor.constraint(equalTo: self.view.layoutMarginsGuide.leadingAnchor).isActive = true
self.myView.trailingAnchor.constraint(equalTo: self.view.layoutMarginsGuide.trailingAnchor).isActive = true
self.myView.topAnchor.constraint(equalTo: self.view.layoutMarginsGuide.topAnchor, constant: 100).isActive = true
self.heightConstarint = self.myView.heightAnchor.constraint(equalToConstant: 100)
self.heightConstarint?.isActive = true
self.mySubview.leadingAnchor.constraint(equalTo: self.myView.layoutMarginsGuide.leadingAnchor).isActive = true
self.mySubview.trailingAnchor.constraint(equalTo: self.myView.layoutMarginsGuide.trailingAnchor).isActive = true
self.mySubview.topAnchor.constraint(equalTo: self.myView.layoutMarginsGuide.topAnchor).isActive = true
self.mySubview.bottomAnchor.constraint(equalTo: self.myView.layoutMarginsGuide.bottomAnchor).isActive = true
self.button.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
self.button.bottomAnchor.constraint(equalTo: self.view.layoutMarginsGuide.bottomAnchor, constant: -20).isActive = true
}
#objc func animateView(_ sender: UIButton){
CATransaction.begin()
CATransaction.setAnimationDuration(5.0)
CATransaction.setAnimationTimingFunction(CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeInEaseOut))
UIView.animate(withDuration: 5.0, animations: {
self.myView.isAnimating = true
self.heightConstarint?.constant = self.heightToAnimate
// this will call `myView.layoutSubviews()`
// and layer's new bound will set automatically
// this causing layer to be directly jump to height 200, instead of smooth animation
self.view.layoutIfNeeded()
}) { (success) in
self.myView.isAnimating = false
}
let shadowPathAnimation = CABasicAnimation(keyPath: #keyPath(CAShapeLayer.shadowPath))
let pathAnimation = CABasicAnimation(keyPath: #keyPath(CAShapeLayer.path))
let toValue = UIBezierPath(
roundedRect:CGRect(x: 0, y: 0, width: self.myView.bounds.width, height: heightToAnimate),
cornerRadius: 10
).cgPath
shadowPathAnimation.fromValue = self.myView.layer.shadowPath
shadowPathAnimation.toValue = toValue
pathAnimation.fromValue = (self.myView.layer as! CAShapeLayer).path
pathAnimation.toValue = toValue
self.myView.layer.shadowPath = toValue
(self.myView.layer as! CAShapeLayer).path = toValue
self.myView.layer.add(shadowPathAnimation, forKey: #keyPath(CAShapeLayer.shadowPath))
self.myView.layer.add(pathAnimation, forKey: #keyPath(CAShapeLayer.path))
CATransaction.commit()
}
}
While animating view, it will call its layoutSubviews() method, which will result into recalculating bounds of shadow layer.
So I checked if view is currently animating, then do not recalculate bounds of shadow layer.
Is this approach right ? or there is any better way to do this ?

Answer 1

I know it's a tricky question. Actually, you don't need to care about layoutSubViews at all. The key here is when you set the shapeLayer. If it's setup well, i.e. after the constraints are all working, you don't need to care that during the animation.
//in CustomView, comment out the layoutSubViews() and add updateLayer()
func updateLayer(){
guard let layer = self.layer as? CAShapeLayer else { return }
layer.path = UIBezierPath(roundedRect: layer.bounds, cornerRadius: 10).cgPath
layer.shadowPath = layer.path
}
// override func layoutSubviews() {
// super.layoutSubviews()
//
// // While animating `myView` height, this method gets called
// // So new bounds for layer will be calculated and set immediately
// // This result in not proper animation
//
// // check by making below condition always true
//
// if !self.isAnimating{ //if true{
// guard let layer = self.layer as? CAShapeLayer else { return }
//
// layer.path = UIBezierPath(roundedRect: bounds, cornerRadius: 10).cgPath
// layer.shadowPath = layer.path
// }
// }
in ViewController: add viewDidAppear() and remove other is animation block
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
myView.updateLayer()
}
#objc func animateView(_ sender: UIButton){
CATransaction.begin()
CATransaction.setAnimationDuration(5.0)
CATransaction.setAnimationTimingFunction(CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeInEaseOut))
UIView.animate(withDuration: 5.0, animations: {
self.heightConstarint?.constant = self.heightToAnimate
// this will call `myView.layoutSubviews()`
// and layer's new bound will set automatically
// this causing layer to be directly jump to height 200, instead of smooth animation
self.view.layoutIfNeeded()
}) { (success) in
self.myView.isAnimating = false
}
....
Then you are good to go. Have a wonderful day.

Answer 2

Below code also worked for me, As I want to use layout subviews without any flags.
UIView.animate(withDuration: 5.0, animations: {
let shadowPathAnimation = CABasicAnimation(keyPath: #keyPath(CAShapeLayer.shadowPath))
let pathAnimation = CABasicAnimation(keyPath: #keyPath(CAShapeLayer.path))
let toValue = UIBezierPath(
roundedRect:CGRect(x: 0, y: 0, width: self.myView.bounds.width, height: self.heightToAnimate),
cornerRadius: 10
).cgPath
shadowPathAnimation.fromValue = self.myView.layer.shadowPath
shadowPathAnimation.toValue = toValue
pathAnimation.fromValue = (self.myView.layer as! CAShapeLayer).path
pathAnimation.toValue = toValue
self.heightConstarint?.constant = self.heightToAnimate
self.myView.layoutIfNeeded()
self.myView.layer.shadowPath = toValue
(self.myView.layer as! CAShapeLayer).path = toValue
self.myView.layer.add(shadowPathAnimation, forKey: #keyPath(CAShapeLayer.shadowPath))
self.myView.layer.add(pathAnimation, forKey: #keyPath(CAShapeLayer.path))
CATransaction.commit()
})
And overriding layoutSubview as follows
override func layoutSubviews() {
super.layoutSubviews()
guard let layer = self.layer as? CAShapeLayer else { return }
layer.path = UIBezierPath(roundedRect: bounds, cornerRadius: 10).cgPath
layer.shadowPath = layer.path
}