CAShapeLayer 出现在 Views 之前

Question

我有两个视图，它们之间位于可调整大小的线（使用 CAShapeLayer 视图）。我面临的问题是，尽管图层上有动画，但它的出现速度比视图的变化快。我知道图层的动画完全不同，但不明白我的错在哪里。如果我做错了什么，请告诉我。

这是我的图层动画的代码（也使用了“strokeStart”，但没有用）：

override func layoutSubviews() {
    super.layoutSubviews()
    let centerX = bounds.size.width / 2
    let path = CGMutablePath()
    path.addLines(between: [CGPoint(x: centerX, y: 0), CGPoint(x: centerX, y: frame.height)])
    dashedLayer.path = path
    dashedLayer.frame = bounds

    let animation = CABasicAnimation(keyPath: "strokeEnd")
    animation.fromValue = height
    animation.toValue = bounds.size.height
    height = bounds.size.height
    animation.duration = 0.3
    dashedLayer.add(animation, forKey: nil)
}

视图动画的代码（因为修改了视图，我为layoutIfNeeded设置了动画）：

UIView.animate(withDuration: 0.3, animations: {
    self.view.layoutIfNeeded()
    ...

Answer 1

我认为解决这个问题的一种简单方法是像这样为约束常量设置动画：

  @IBOutlet weak  var heightConstraint: NSLayoutConstraint!

  UIView.animate(withDuration: 3, animations: {

        self. heightConstaint.constant = 300 // This constant is the height of top big view. 

        self.view.layoutIfNeeded()}

CAShapeLayer 所在的另一个视图。我称之为line View。它的高度应限制为与top big view 的高度相同。

在line view，可以添加动画。这应该与您的实现类似。

   override func didMoveToSuperview() {
     super.didMoveToSuperview()
     dashedLayer.backgroundColor = UIColor.clear.cgColor
     layer.addSublayer(dashedLayer)
     height = bounds.size.height
   }

  override func layoutSubviews() {
    super.layoutSubviews()
    let centerX = bounds.size.width / 2
    let path = CGMutablePath()
    path.addLines(between: [CGPoint(x: centerX, y: 0), CGPoint(x: centerX, y: frame.height)])
    dashedLayer.path = path
    dashedLayer.lineWidth = 3.0
    dashedLayer.strokeColor = UIColor.blue.cgColor

    let animation = CABasicAnimation(keyPath: "strokeEnd")
    animation.fromValue = height / bounds.size.height
    animation.toValue = 1.0 
    animation.timingFunction = CAMediaTimingFunction.init(name: CAMediaTimingFunctionName.easeInEaseOut)
    height = bounds.size.height
    animation.duration = 3.0
    dashedLayer.add(animation, forKey: nil)
}

这里正在扩展。您可以自己修改代码以适应合同。

以下是倒车动画。

override func didMoveToSuperview() {
    super.didMoveToSuperview()
    dashedLayer.backgroundColor = UIColor.clear.cgColor
    layer.addSublayer(dashedLayer)
    height = bounds.size.height
      clipsToBounds = true
}


override func layoutSubviews() {
    super.layoutSubviews()
    let centerX = bounds.size.width / 2
    let path = CGMutablePath()
    path.addLines(between: [CGPoint(x: centerX, y: 0), CGPoint(x: centerX, y: max(height , bounds.size.height) )])
    dashedLayer.path = path
    dashedLayer.lineWidth = 3.0
    dashedLayer.strokeColor = UIColor.blue.cgColor

    let animation = CABasicAnimation(keyPath: "strokeEnd")

    if (height < bounds.size.height){
    animation.fromValue = height / bounds.size.height
        animation.toValue = 1.0}

    else {
        animation.fromValue = 1.0
        animation.toValue = bounds.size.height / height}


    animation.timingFunction = CAMediaTimingFunction.init(name: CAMediaTimingFunctionName.easeInEaseOut)
    height = bounds.size.height
    animation.duration = 3
    dashedLayer.add(animation, forKey: nil)
}

Answer 2

您当前的代码存在一些问题。目前您正在更改没有动画的路径，因此它会立即更新。 strokeEnd 的值也是 0 到 1，所以现在你的路径总是有一个完整的笔划。

您应该为路径更改而不是笔划设置动画。

override func layoutSubviews() {
    super.layoutSubviews()
    let centerX = bounds.size.width / 2
    let path = CGMutablePath()
    path.addLines(between: [CGPoint(x: centerX, y: 0), CGPoint(x: centerX, y: frame.height)])
    dashedLayer.path = path
    dashedLayer.frame = bounds

    let animation = CABasicAnimation(keyPath: "path")
    animation.duration = 0.3
    animation.fromValue = dashedLayer.path
    animation.toValue = path
    dashedLayer.add(animation, forKey: "pathAnimation")
}