CAShapelayer重复

Question

我试图在给定的x和y坐标中每20 to添加一次CAShapelayer。我希望这个形状在一秒内消失(就像一个示踪剂)。我创建的函数作品，形状是创建在正确的位置和消失。但我的屏幕上有多余的形状。

func shadowBall (x: CGFloat, y: CGFloat){

    let xpos : CGFloat = ((self.frame.width/2) + x)
    let ypos : CGFloat = ((self.frame.height/2) + y)

    let shadowBall = CAShapeLayer()
    let shadowBalllRadius :CGFloat = 4
    let shadowBallPath : UIBezierPath = UIBezierPath(ovalInRect: CGRect(x: xpos, y: ypos, width: CGFloat(shadowBalllRadius*2), height: CGFloat(shadowBalllRadius*2)))

    shadowBall.path = shadowBallPath.CGPath
    shadowBall.fillColor = UIColor.clearColor().CGColor
    shadowBall.strokeColor = UIColor.whiteColor().CGColor
    shadowBall.lineWidth = 0.5

    let animation: CABasicAnimation = CABasicAnimation(keyPath: "strokeColor")
    animation.fromValue = UIColor.whiteColor().CGColor
    animation.toValue = UIColor.clearColor().CGColor
    animation.duration = 1.0;
    animation.repeatCount = 0;
    animation.removedOnCompletion = true
    animation.additive = false

    self.layer.addSublayer(shadowBall)
    shadowBall.addAnimation(animation, forKey: "strokeColor")

}

Answer 1

问题是，当动画完成后，它会将strokeColor恢复到原来的颜色。您应该将原始形状层的strokeColor设置为clearColor()，这样，当您完成从whiteColor()到clearColor()的动画时，它将保留在clearColor()上。

您还可以将图层的fillMode设置为kCAFillModeForwards，将removedOnCompletion设置为false，这将使图层保留其“结束动画”状态。但我个人只想设置上面概述的strokeColor，因为使用removedOnCompletion of true会干扰animationDidStop (见下文)。

此外，我可能建议您也删除图层，一旦它完成了动画，这样它就不会继续消耗内存，尽管它不再可见。

func shadowBall (x: CGFloat, y: CGFloat) {
    let xpos: CGFloat = ((self.frame.width/2) + x)
    let ypos: CGFloat = ((self.frame.height/2) + y)

    let shadowBall = CAShapeLayer()
    let shadowBalllRadius: CGFloat = 4
    let shadowBallPath = UIBezierPath(ovalInRect: CGRect(x: xpos, y: ypos, width: CGFloat(shadowBalllRadius*2), height: CGFloat(shadowBalllRadius*2)))

    shadowBall.path = shadowBallPath.CGPath
    shadowBall.fillColor = UIColor.clearColor().CGColor
    shadowBall.strokeColor = UIColor.clearColor().CGColor
    shadowBall.lineWidth = 0.1

    let animation = CABasicAnimation(keyPath: "strokeColor")
    animation.fromValue = UIColor.whiteColor().CGColor
    animation.toValue = UIColor.clearColor().CGColor
    animation.duration = 1.0
    animation.repeatCount = 0
    animation.removedOnCompletion = true
    animation.additive = false

    animation.delegate = self
    animation.setValue(shadowBall, forKey: "animationLayer")

    self.layer.addSublayer(shadowBall)
    shadowBall.addAnimation(animation, forKey: "strokeColor")
}

override func animationDidStop(anim: CAAnimation, finished flag: Bool) {
    if let layer = anim.valueForKey("animationLayer") as? CALayer {
        layer.removeFromSuperlayer()
    }
}

请参阅How to remove a CALayer-object from animationDidStop?