iOS 复杂动画之抽丝剥茧

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！

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

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

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

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

}

}

然后设置圆角

lineCap = kCALineCapRound

lineJoin = kCALineJoinRound

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

然后同理，保持中心不变分别按顺序向右和向上拉伸

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

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

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)

}

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)

}

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)

}

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)

}

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

六、最后

同样，还是提供了两个版本（Objective-C & Swift），你可以在 这里 查看源码！

一直对动画比较感兴趣，希望多研究多深入，有什么意见或者建议的话，可以留言或者私信，如果觉得还好的话，请star支持，谢谢！