本文授权转载，作者：HenryCheng（微博）
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！
1466346770878893.gif
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
1466346840901497.gif
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
1466346876652751.gif
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
}
}
1466346913677135.png
然后设置圆角
1
2
lineCap = kCALineCapRound
lineJoin = kCALineJoinRound
1466346937206965.png
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
1466346949882231.gif
然后同理，保持中心不变分别按顺序向右和向上拉伸
1466346960871367.gif
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
1466346987587957.gif
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
1466346997443563.gif
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)
}
1466347034403843.gif
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)
}
1466347061781547.gif
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)
}
1466347085312463.gif
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)
}
1466347106531532.gif
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
1466347148388339.gif
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！
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