How to add a CAGradientLayer to a UIView when using programmatic constraints

Question

For an iOS app in Swift, I am using programmatic constraints and would like to add a CAGradientLayer() to a UIView(). Below is my code which doesn't work.

   import UIKit

   class ViewController: UIViewController {

       let animationView: UIView = {
           let view = UIView()
           view.translatesAutoresizingMaskIntoConstraints = false
           return view
       }()

       override func viewDidLoad() {
           super.viewDidLoad()

           view.addSubview(animationView)
           setupAnimationView()
           animationView.addGradientLayer()
       }

       func setupAnimationView() {
           animationView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
           animationView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
           animationView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
           animationView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
       }
   }

   extension UIView {

       func addGradientLayer() {
           let color1 = UIColor(red: 251/255, green: 55/255, blue: 91/255, alpha: 1.0)
           let color2 = UIColor(red: 1.0, green: 70/255, blue: 0, alpha: 1.0)
           let gradientLayer = CAGradientLayer()
           gradientLayer.name = "gradientLayer"
           gradientLayer.frame = self.frame
           gradientLayer.colors = [color1.cgColor, color2.cgColor]
           self.layer.insertSublayer(gradientLayer, at: 0)
       }
   }

The issue I am having I believe is related to the fact that I create animationView with programmatic constraints and I then try and add the gradient layer by setting its frame equal to the view of the frame. This code works when I don't use programmatic constraints. Any ideas what I am missing / doing wrong?

Answer 1

Any layers that you add to the view will not be managed under AutoLayout and there isn't a way to make this happen.

What you can do is store the layer as a property (perhaps on the view controller).

Then in the method...

override func viewDidLayoutSubviews() {
    super.viewDIdLayoutSubviews()
    // update the layers frame based on the frame of the view.
}

In this method the view will have it's proper frame so if it has changed you will need to update the layer to have a new frame accordingly.