IOS Animation-CAShapeLayer、UIBezierPath与Animation的结合

在阅读本文之前，对CAShapeLayer、UIBezierPath不熟悉的话，可以先阅读文章 贝塞尔曲线与Layer

如果对动画不熟悉的话，先阅读文章 动画基础、深入

Layer是绘图的画板，Bezier是画图的画笔，Animation是画图的动作。现在我们可以通过下面例子更好的让它们更好地结合在一起。

1）画一个小屋子动画

我们首先通过定义CAShapeLayer画板，然后定义path来确定画图路径。最后使用动画。如下面代码

     //让一个屋子的线画起来的动画效果
     func addCAShapeLayerAnimationStrokeEnd() {
         //创建CAShapeLayer，屋子的layer
         let slayer = CAShapeLayer.init()
         slayer.strokeColor = UIColor.blackColor().CGColor
         slayer.fillColor = UIColor.clearColor().CGColor

         //创建屋子的路径path
         let path = UIBezierPath.init()
         path.moveToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))

         //把画图的路径path添加到layer中
         slayer.path = path.CGPath
         //添加slayer到view.layer
         self.view.layer.addSublayer(slayer)

         //创建动画，strokeEnd。让线画起来的效果
         let ani = CABasicAnimation(keyPath: "strokeEnd")
         ani.fromValue =
         ani.toValue =
         ani.repeatCount =
         ani.duration = 

         slayer.addAnimation(ani, forKey: "addCAShapeLayerAnimationStrokeEnd")
     }

2）小屋子+画笔的动画

上面1）中我们画了一个屋子的动画，那么如果我们想在屋子上面添加一个画笔来画，让动画更加生动。所以我们用到keyframe动画来添加path。

     //让一个屋子的线画起来的动画效果
     func addCAShapeLayerAnimationStrokeEnd2() {
         //---创建CAShapeLayer，屋子的layer start---
         let pathLayer = CAShapeLayer.init()
         pathLayer.strokeColor = UIColor.blackColor().CGColor
         pathLayer.fillColor = UIColor.clearColor().CGColor
         //创建屋子的路径path
         let path = UIBezierPath.init()
         path.moveToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))
         path.addLineToPoint(CGPointMake(, ))
         //把画图的路径path添加到layer中
         pathLayer.path = path.CGPath
         //添加slayer到view.layer
         self.view.layer.addSublayer(pathLayer)
         //---创建CAShapeLayer，屋子的layer end---

         //---创建画笔layer start---
         let panLayer = CALayer.init()
         panLayer.anchorPoint = CGPointZero
         panLayer.frame = CGRectMake(, , , )
         panLayer.contents = UIImage(named: "pan.png")?.CGImage
         self.view.layer.addSublayer(panLayer)
         //---创建画笔layer end---

         //---创建动画，strokeEnd。让线画起来的效果 start---
         let strokeEndAnimation = CABasicAnimation(keyPath: "strokeEnd")
         strokeEndAnimation.fromValue =
         strokeEndAnimation.toValue =
         strokeEndAnimation.repeatCount =
         strokeEndAnimation.duration =
         pathLayer.addAnimation(strokeEndAnimation, forKey: "strokeEndAnimation")
         //---创建动画，strokeEnd。让线画起来的效果 end---

         //---让画笔动起来动画start---
         let panAnimation = CAKeyframeAnimation(keyPath: "position")
         panAnimation.path = path.CGPath
         panAnimation.calculationMode = kCAAnimationPaced
         panAnimation.duration =
         panAnimation.repeatCount =
         panLayer.addAnimation(panAnimation, forKey: "panAnimation")
         //---让画笔动起来动画end---

     }