ios - 使用自动布局为 UIView 应用渐变背景

Question

我扩展了 UIView 以添加一个 addGradientWithColor() 方法来获取渐变背景:

 extension UIView {
   func addGradientWithColor() {
     let gradient = CAGradientLayer()
     gradient.frame = self.bounds
     gradient.colors = [gradientEndColor.CGColor,  gradientStartColor.CGColor]
     gradient.startPoint = CGPointMake(1,0)
     gradient.endPoint = CGPointMake(0.2,1)
    self.layer.insertSublayer(gradient, atIndex: 0)
  } } 

我的问题是当我运行横向模式时，UIView 没有拉伸(stretch)

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    self.view.addGradientWithColor() }

我尝试调用 viewDidLayoutSubviews() 但它无法正常工作

这是屏幕截图:

移除 viewDidLayoutSubviews() 后

Answer 1

您可以子类化 UIView 并在添加渐变的地方覆盖 drawRect 方法。

已更新至 Swift 4

class GradientView: UIView {

    private let gradient : CAGradientLayer = CAGradientLayer()
    private let gradientStartColor: UIColor
    private let gradientEndColor: UIColor

    init(gradientStartColor: UIColor, gradientEndColor: UIColor) {
        self.gradientStartColor = gradientStartColor
        self.gradientEndColor = gradientEndColor
        super.init(frame: .zero)
    }

    required init?(coder aDecoder: NSCoder) { fatalError("init(coder:) has not been implemented") }

    override func layoutSublayers(of layer: CALayer) {
        super.layoutSublayers(of: layer)
        gradient.frame = self.bounds
    }

    override public func draw(_ rect: CGRect) {
        gradient.frame = self.bounds
        gradient.colors = [gradientEndColor.cgColor, gradientStartColor.cgColor]
        gradient.startPoint = CGPoint(x: 1, y: 0)
        gradient.endPoint = CGPoint(x: 0.2, y: 1)
        if gradient.superlayer == nil {
            layer.insertSublayer(gradient, at: 0)
        }
    }
}

创建 UIView 后，您只需向该 View 添加约束。