使用编程约束时如何将 CAGradientLayer 添加到 UIView

问题描述：

对于 Swift 中的 iOS 应用程序，我正在使用编程约束并想将 CAGradientLayer() 添加到 UIView().下面是我的代码，它不起作用.

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)
       }
   }

我认为我遇到的问题与以下事实有关，即我使用编程约束创建了 animationView，然后我尝试通过将其框架设置为等于框架视图来添加渐变层.当我不使用编程约束时，此代码有效.任何想法我错过/做错了什么?

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?

答

您添加到视图中的任何图层都不会在 AutoLayout 下进行管理，并且没有办法实现这一点.

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

您可以做的是将图层存储为属性(可能在视图控制器上).

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

然后在方法中...

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

在这种方法中，视图将拥有正确的框架，因此如果它发生了变化，您将需要相应地更新图层以拥有一个新框架.

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.

使用编程约束时如何将 CAGradientLayer 添加到 UIView

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