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iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

一、前言

随着开发者的增多和时间的累积，AppStore已经有非常多的应用了，每年都有很多新的APP产生。但是我们手机上留存的应用有限，所以如何吸引用户，成为产品设计的一项重要内容。其中炫酷的动画效果是重要内容之一，我们会发现很多好的应用上面都有许多很炫的效果。可能一提到炫酷的动画，很多人都很头疼，因为动画并不是那么好做，实现一个好的动画需要时间、耐心和好的思路。下面我们就以一个有趣的动画（如下图）为例，抽丝剥茧，看看到底是怎么实现的！

编辑：Bison

投稿： HenryCheng

二、分析

上面图中的动画第一眼看起来的确是有点复杂，但是我们来一步步分析，就会发现其实并不是那么难。仔细看一下就会发现，大致步骤如下：

1、先出来一个圆 2、圆形在水平和竖直方向上被挤压，呈椭圆形状的一个过程，最后恢复成圆形 3、圆形的左下角、右下角和顶部分别按顺序凸出一小部分 4、圆和凸出部分形成的图形旋转一圈后变成三角形 5、三角形的左边先后出来两条宽线，将三角形围在一个矩形中 6、矩形由底部向上被波浪状填满 7、被填满的矩形放大至全屏，弹出Welcome 动画大致就分为上面几个步骤，拆分后我们一步步来实现其中的效果（下面所示步骤中以Swift代码为例，demo中分别有Objective-C和Swift的实现）。

三、实现圆形以及椭圆的渐变

首先，我们创建了一个新工程后，然后新建了一个名AnimationView的类继承UIView，这个是用来显示动画效果的一个view。然后先添加CircleLayer（圆形layer），随后实现由小变大的效果。

 class AnimationView: UIView {        let circleLayer = CircleLayer()        override init(frame: CGRect) {            super.init(frame: frame)            backgroundColor = UIColor.clearColor()            addCircleLayer()        }        required init?(coder aDecoder: NSCoder) {            super.init(coder: aDecoder)        }        /**        add circle layer        */       func addCircleLayer() {            self.layer.addSublayer(circleLayer)            circleLayer.expand()        }   }

其中expand()这个方法如下

/**  expand animation function  */ func expand() {     let expandAnimation: CABasicAnimation = CABasicAnimation(keyPath: "path")     expandAnimation.fromValue = circleSmallPath.CGPath     expandAnimation.toValue = circleBigPath.CGPath     expandAnimation.duration = KAnimationDuration     expandAnimation.fillMode = kCAFillModeForwards     expandAnimation.removedOnCompletion = false     self.addAnimation(expandAnimation, forKey: nil) }

运行效果如下

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

第一步做好了，接下来就是呈椭圆形状的变化了，仔细分析就比如一个弹性小球，竖直方向捏一下，水平方向捏一下这样的效果。这其实就是一个组合动画，如下

/**  wobbl group animation  */ func wobbleAnimate() {     // 1、animation begin from bigPath to verticalPath     let animation1: CABasicAnimation = CABasicAnimation(keyPath: "path")     animation1.fromValue = circleBigPath.CGPath     animation1.toValue = circleVerticalSquishPath.CGPath     animation1.beginTime = KAnimationBeginTime     animation1.duration = KAnimationDuration      // 2、animation vertical to horizontal     let  animation2: CABasicAnimation = CABasicAnimation(keyPath: "path")     animation2.fromValue = circleVerticalSquishPath.CGPath     animation2.toValue = circleHorizontalSquishPath.CGPath     animation2.beginTime = animation1.beginTime + animation1.duration     animation2.duration = KAnimationDuration      // 3、animation horizontal to vertical     let  animation3: CABasicAnimation = CABasicAnimation(keyPath: "path")     animation3.fromValue = circleHorizontalSquishPath.CGPath     animation3.toValue = circleVerticalSquishPath.CGPath     animation3.beginTime = animation2.beginTime + animation2.duration     animation3.duration = KAnimationDuration      // 4、animation vertical to bigPath     let  animation4: CABasicAnimation = CABasicAnimation(keyPath: "path")     animation4.fromValue = circleVerticalSquishPath.CGPath     animation4.toValue = circleBigPath.CGPath     animation4.beginTime = animation3.beginTime + animation3.duration     animation4.duration = KAnimationDuration      // 5、group animation     let animationGroup: CAAnimationGroup = CAAnimationGroup()     animationGroup.animations = [animation1, animation2, animation3, animation4]     animationGroup.duration = 4 * KAnimationDuration     animationGroup.repeatCount = 2     addAnimation(animationGroup, forKey: nil) }

上面代码中实现了从圆 → 椭圆（x方向长轴）→ 椭圆（y方向长轴）→ 圆这一系列的变化，最后组合成一个动画。这一步实现后效果如下

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

四、实现圆形边缘的凸出部分

关于这个凸出部分，乍一看可能感觉会比较难实现，看起来挺复杂的。其实实现的原理很简单，仔细分析我们会发现这三个凸出部分连起来刚好是一个三角形，那么第一步我们就在之前的基础上先加一个三角形的layer，如下

import UIKit  class TriangleLayer: CAShapeLayer {      let paddingSpace: CGFloat = 30.0      override init() {          super.init()         fillColor = UIColor.colorWithHexString("#009ad6").CGColor         strokeColor = UIColor.colorWithHexString("#009ad6").CGColor         lineWidth = 7.0         path = smallTrianglePath.CGPath     }      required init?(coder aDecoder: NSCoder) {         fatalError("init(coder:) has not been implemented")     }      var smallTrianglePath: UIBezierPath {         let smallPath = UIBezierPath()         smallPath.moveToPoint(CGPointMake(5.0 + paddingSpace, 95.0))         smallPath.addLineToPoint(CGPointMake(50.0, 12.5 + paddingSpace))         smallPath.addLineToPoint(CGPointMake(95.0 - paddingSpace, 95.0))         smallPath.closePath()         return smallPath     } }

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

然后设置圆角

    lineCap = kCALineCapRound     lineJoin = kCALineJoinRound

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift) 下面就是来做凸出部分了，原理其实很简单，就是将现在这个三角形保持中心不变，左边向左延伸即可

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

然后同理，保持中心不变分别按顺序向右和向上拉伸

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

具体过程是这样的

/**  triangle animate function  */ func triangleAnimate() {      // left     let triangleAnimationLeft: CABasicAnimation = CABasicAnimation(keyPath: "path")     triangleAnimationLeft.fromValue = smallTrianglePath.CGPath     triangleAnimationLeft.toValue = leftTrianglePath.CGPath     triangleAnimationLeft.beginTime = 0.0     triangleAnimationLeft.duration = 0.3      // right     let triangleAnimationRight: CABasicAnimation = CABasicAnimation(keyPath: "path")     triangleAnimationRight.fromValue = leftTrianglePath.CGPath     triangleAnimationRight.toValue = rightTrianglePath.CGPath     triangleAnimationRight.beginTime = triangleAnimationLeft.beginTime + triangleAnimationLeft.duration     triangleAnimationRight.duration = 0.25      // top     let triangleAnimationTop: CABasicAnimation = CABasicAnimation(keyPath: "path")     triangleAnimationTop.fromValue = rightTrianglePath.CGPath     triangleAnimationTop.toValue = topTrianglePath.CGPath     triangleAnimationTop.beginTime = triangleAnimationRight.beginTime + triangleAnimationRight.duration     triangleAnimationTop.duration = 0.20      // group     let triangleAnimationGroup: CAAnimationGroup = CAAnimationGroup()     triangleAnimationGroup.animations = [triangleAnimationLeft, triangleAnimationRight, triangleAnimationTop]     triangleAnimationGroup.duration = triangleAnimationTop.beginTime + triangleAnimationTop.duration     triangleAnimationGroup.fillMode = kCAFillModeForwards     triangleAnimationGroup.removedOnCompletion = false     addAnimation(triangleAnimationGroup, forKey: nil) }

我们接下来把三角形的颜色改一下

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

这里颜色相同了我们就可以看到了这个凸出的这个效果，调到正常速率（为了演示，把动画速率调慢了），联合之前所有的动作，到现在为止，效果是这样的

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

到现在为止，看上去还不错，差不多已经完成一半了，继续下一步！

五、实现旋转和矩形

旋转来说很简单了，大家估计都做过旋转动画，这里就是把前面形成的图形旋转一下（当然要注意设置锚点anchorPoint）

/**  self transform z  */ func transformRotationZ() {     self.layer.anchorPoint = CGPointMake(0.5, 0.65)     let rotationAnimation: CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")     rotationAnimation.toValue = CGFloat(M_PI * 2)     rotationAnimation.duration = 0.45     rotationAnimation.removedOnCompletion = true     layer.addAnimation(rotationAnimation, forKey: nil) }

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

旋转之后原图形被切成了一个三角形，思路就是把原来的大圆，按着这个大三角形的内切圆剪切一下即可

/**  contract animation function  */ func contract() {     let contractAnimation: CABasicAnimation = CABasicAnimation(keyPath: "path")     contractAnimation.fromValue = circleBigPath.CGPath     contractAnimation.toValue = circleSmallPath.CGPath     contractAnimation.duration = KAnimationDuration     contractAnimation.fillMode = kCAFillModeForwards     contractAnimation.removedOnCompletion = false     addAnimation(contractAnimation, forKey: nil) }

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

接下来就是画矩形，新建一个RectangleLayer，划线

/**  line stroke color change with custom color   - parameter color: custom color  */ func strokeChangeWithColor(color: UIColor) {     strokeColor = color.CGColor     let strokeAnimation: CABasicAnimation = CABasicAnimation(keyPath: "strokeEnd")     strokeAnimation.fromValue = 0.0     strokeAnimation.toValue = 1.0     strokeAnimation.duration = 0.4     addAnimation(strokeAnimation, forKey: nil) }

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

最后面就是经典的水波纹动画了，不多说，直接上代码

func animate() {      /// 1     let waveAnimationPre: CABasicAnimation = CABasicAnimation(keyPath: "path")     waveAnimationPre.fromValue = wavePathPre.CGPath     waveAnimationPre.toValue = wavePathStarting.CGPath     waveAnimationPre.beginTime = 0.0     waveAnimationPre.duration = KAnimationDuration      /// 2     let waveAnimationLow: CABasicAnimation = CABasicAnimation(keyPath: "path")     waveAnimationLow.fromValue = wavePathStarting.CGPath     waveAnimationLow.toValue = wavePathLow.CGPath     waveAnimationLow.beginTime = waveAnimationPre.beginTime + waveAnimationPre.duration     waveAnimationLow.duration = KAnimationDuration      /// 3     let waveAnimationMid: CABasicAnimation = CABasicAnimation(keyPath: "path")     waveAnimationMid.fromValue = wavePathLow.CGPath     waveAnimationMid.toValue = wavePathMid.CGPath     waveAnimationMid.beginTime = waveAnimationLow.beginTime + waveAnimationLow.duration     waveAnimationMid.duration = KAnimationDuration      /// 4     let waveAnimationHigh: CABasicAnimation = CABasicAnimation(keyPath: "path")     waveAnimationHigh.fromValue = wavePathMid.CGPath     waveAnimationHigh.toValue = wavePathHigh.CGPath     waveAnimationHigh.beginTime = waveAnimationMid.beginTime + waveAnimationMid.duration     waveAnimationHigh.duration = KAnimationDuration      /// 5     let waveAnimationComplete: CABasicAnimation = CABasicAnimation(keyPath: "path")     waveAnimationComplete.fromValue = wavePathHigh.CGPath     waveAnimationComplete.toValue = wavePathComplete.CGPath     waveAnimationComplete.beginTime = waveAnimationHigh.beginTime + waveAnimationHigh.duration     waveAnimationComplete.duration = KAnimationDuration      /// group animation     let arcAnimationGroup: CAAnimationGroup = CAAnimationGroup()     arcAnimationGroup.animations = [waveAnimationPre, waveAnimationLow, waveAnimationMid, waveAnimationHigh, waveAnimationComplete]     arcAnimationGroup.duration = waveAnimationComplete.beginTime + waveAnimationComplete.duration     arcAnimationGroup.fillMode = kCAFillModeForwards     arcAnimationGroup.removedOnCompletion = false     addAnimation(arcAnimationGroup, forKey: nil) }

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)

找几个点控制水波形状，画出贝塞尔曲线即可，到这里基本就完成了。接下来最后一步，放大，并弹出Welcome

func expandView() {     backgroundColor = UIColor.colorWithHexString("#40e0b0")     frame = CGRectMake(frame.origin.x - blueRectangleLayer.lineWidth,                        frame.origin.y - blueRectangleLayer.lineWidth,                        frame.size.width + blueRectangleLayer.lineWidth * 2,                        frame.size.height + blueRectangleLayer.lineWidth * 2)     layer.sublayers = nil      UIView.animateWithDuration(0.3, delay: 0.0, options: UIViewAnimationOptions.CurveEaseInOut, animations: {         self.frame = self.parentFrame         }, completion: { finished in             self.delegate?.completeAnimation()     })  }

放大完以后设置代理，然后在主的vc中添加Welcome这个Label

// MARK: - // MARK: AnimationViewDelegate func completeAnimation() {     // 1     animationView.removeFromSuperview()     view.backgroundColor = UIColor.colorWithHexString("#40e0b0")      // 2     let label: UILabel = UILabel(frame: view.frame)     label.textColor = UIColor.whiteColor()     label.font = UIFont(name: "HelveticaNeue-Thin", size: 50.0)     label.textAlignment = NSTextAlignment.Center     label.text = "Welcome"     label.transform = CGAffineTransformScale(label.transform, 0.25, 0.25)     view.addSubview(label)      // 3     UIView.animateWithDuration(0.4, delay: 0.0, usingSpringWithDamping: 0.7, initialSpringVelocity: 0.1, options: UIViewAnimationOptions.CurveEaseInOut,animations: ({              label.transform = CGAffineTransformScale(label.transform, 4.0, 4.0)         }), completion: { finished in             self.addTouchButton()     })  }

到现在为止，动画全部完成

iOS开发之复杂动画之抽丝剥茧(Objective-C & Swift)