减慢 CAGradientLayer 动画

Question

我想慢慢地制作一个三色渐变的动画。

我有一个自定义的UIView，如下所示：

class MyView: UIView, CAAnimationDelegate {

  lazy var gradientLayer: CAGradientLayer = {
        let l = CAGradientLayer()
        l.frame = self.frame
        l.colors = self.colors
        l.startPoint = CGPoint(x: 0, y: 0)
        l.endPoint = CGPoint(x: 1, y: 0)
        l.mask = self.textLayer
        return l
    }()

    lazy var textLayer: CATextLayer = {
        let l = CATextLayer()
        l.frame = self.frame
        l.string = "test".uppercased()
        l.fontSize = 23
        return l
    }()

    var colors: [CGColor] =  [
            UIColor.red.cgColor,
            UIColor.purple.cgColor,
            UIColor.blue.cgColor
            ]

    init() {
    ...
    self.layer.addSublayer(gradientLayer)

    }

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

    func animate() {

      var newColors = colors
      let lastColor: CGColor = newColors.last!
      newColors.removeLast()
      newColors.insert(lastColor, at: 0)

      colors: newColors
      gradientLayer.colors = newColors

      let a = CABasicAnimation(keyPath:"colors")
      a.toValue = newColors
      a.duration = 0.1
      a.isRemovedOnCompletion = true
      a.fillMode = kCAFillModeForwards
      a.delegate = self

      gradientLayer.add(a, forKey:"animateGradient")

    }

    func animationDidStop(_ anim: CAAnimation, finished flag: Bool) {

          animate()
    }

}

这可行，但速度非常快。我怎样才能减慢动画速度，而不会变得块状？ 我是否必须在 colors 数组中添加几百种颜色，以便它有足够的循环时间？

谢谢

Answer 1

除非我在您的代码中遗漏了某些内容，否则您没有在动画中设置 fromValue。当然，在将颜色切换为 newColors 之前，您需要将其设置为以前的颜色值：

func animate() {
  let oldColors = colors
  var newColors = colors
  let lastColor: CGColor = newColors.last!
  newColors.removeLast()
  newColors.insert(lastColor, at: 0)

  colors = newColors
  gradientLayer.colors = newColors

  let a = CABasicAnimation(keyPath:"colors")
  // New line here ->
  a.fromValue = oldColors
  a.toValue = newColors
  a.duration = 0.1
  a.isRemovedOnCompletion = true
  a.fillMode = kCAFillModeForwards
  a.delegate = self

  gradientLayer.add(a, forKey:"animateGradient")

}

这将是您没有真正获得动画的原因 - 您的代码被有效地设置为创建延迟的快照过渡。