CAShapelayer重複

Question

我想添加一個CAShapelayer每20ms一次給定的x和y座標。我希望這個形狀能夠在一秒之內消失（就像一個示蹤劑）。我創建的函數工作，形狀創建在正確的位置並消失。但是我得到了額外的形狀留在屏幕上。

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

問題是，當動畫結束時，它會將strokeColor恢復爲原始顏色。您應該將原始形狀圖層的strokeColor設置爲clearColor()，這樣，當您完成從whiteColor()到clearColor()的動畫時，它將保持在clearColor()。

您還可以設置圖層的fillMode到kCAFillModeForwards並設置removedOnCompletion到false，並且將有層保持其狀態「動畫的結束」。但我個人只會設置strokeColor如上所述，因爲使用removedOnCompletiontrue干擾animationDidStop（見下文）。

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另外，我可能會建議您在動畫完成後也刪除圖層，以免它繼續佔用內存，儘管它不再可見。

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() 
    } 
} 

見How to remove a CALayer-object from animationDidStop?