Swift 卡巴斯基化反向（向后）

我有点挣扎与这个简单的线动画。我知道如何暂停，但我需要的是能够从调用函数resetAnimation（）的那一刻起将动画反转回起始点

let path animation=cabasicanition（关键路径：“strokeEnd”）
让pathLayer=CAShapeLayer（）
func线性化（）{
let path=UIBezierPath（）
让screenWidth=self.view.bounds.width
让屏幕高度=self.view.bounds.height
path.moveToPoint（CGPointMake（屏幕宽度、屏幕高度/2））
path.addLineToPoint（CGPointMake（屏幕宽度-屏幕宽度，屏幕高度/2））
self.pathLayer.frame=self.view.bounds
self.pathLayer.path=path.CGPath
self.pathLayer.strokeColor=UIColor.whiteColor（）.CGColor
self.pathLayer.fillColor=nil
self.pathLayer.lineWidth=3.0
self.pathLayer.lineCap=kcalinecapound
self.pathLayer.speed=1
self.view.layer.addSublayer（路径层）
self.pathAnimation.duration=5.0
self.pathAnimation.fromValue=0.0
self.pathAnimation.toValue=1.0
addAnimation（路径动画，forKey：“动画”）
}
函数pauseAnimation（）{
让pausedTime=pathLayer.convertTime（CACurrentMediaTime（），fromLayer:nil）
pathLayer.speed=0
pathLayer.timeOffset=pausedTime
}
函数重置动画（）{
}

您只需创建一个新动画并删除旧动画即可。新动画的起点将是表示层中该特性的当前值。我还建议您将形状层的框架设置为实际贝塞尔形状的边界，而不是整个视图-当您开始四处移动、缩放/旋转等时，这是一个好习惯。否则您将面临一系列时髦的转换或锚定点更改

下面是我要做的：

let pathLayer = CAShapeLayer()

// first, separate your drawing code from your animation code.
// this way you can call animations without instantiating new objects
func drawLine() {
    let path = UIBezierPath()
    // draw your path with no position translation.. move the layer
    path.moveToPoint(CGPointMake(view.bounds.width, 0))
    path.addLineToPoint(CGPointMake(0, 0))
    pathLayer.frame = path.bounds
    // this line sets the position of the layer appropriately
    pathLayer.position = view.bounds.width - pathLayer.bounds.width / 2
    pathLayer.path = path.CGPath
    pathLayer.strokeColor = UIColor.whiteColor().CGColor
    pathLayer.fillColor = nil
    pathLayer.lineWidth = 3.0
    pathLayer.lineCap = kCALineCapRound
    view.layer.addSublayer(pathLayer)
}

func lineAnimation() {
    let pathAnimation = CABasicAnimation(keyPath: "strokeEnd")
    pathAnimation.duration = 5.0
    pathAnimation.fromValue = 0.0
    pathAnimation.toValue = 1.0
    pathLayer.addAnimation(pathAnimation, forKey: "strokeEnd")

}

func reverseAnimation() {
    let revAnimation = CABasicAnimation(keyPath: "strokeEnd")
    revAnimation.duration = 5.0
    // every Core Animation has a 'presentation layer' that contains the animated changes
    revAnimation.fromValue = pathLayer.presentationLayer()?.strokeEnd
    revAnimation.toValue = 0.0
    pathLayer.removeAllAnimations()
    pathLayer.addAnimation(revAnimation, forKey: "strokeEnd")
}

---

请记住，您还需要设置属性，以便保留动画的结束值。

您还可以使用

CAMediaTiming

协议的

自动反转

属性，通过

cabasicaniation

以特定速度倒车，或仅在on go？中完全重置回初始设置以特定速度倒车Swift 4.1的API更新：revAnimation.fromValue=pathLayer.presentation（）？.strokeEnd