执行完后就跟上图一样的效果了~~~
动画分解
经过分析，可以将动画分为四个步骤：
•画布的旋转动画，旋转两圈
•线条由长变短的动画，更画布选择的动画一起执行，旋转一圈的时候结束
•线条的位移动画，线条逐渐向中间靠拢，再画笔旋转完一圈的时候执行，两圈的时候结束
•线条由短变长的动画，画布旋转完两圈的时候执行
第一步画布旋转动画
这里我们使用CABasicAnimation基础动画，keyPath作用于画布的transform.rotation.z，以z轴为目标进行旋转，下面是效果图和代码：
//MARK: 动画步骤
/**
旋转的动画，旋转两圈
*/
private func angleAnimation() {
let angleAnimation = CABasicAnimation.init(keyPath: "transform.rotation.z")
angleAnimation.fromValue = angle(-30)
angleAnimation.toValue = angle(690)
angleAnimation.fillMode = kCAFillModeForwards
angleAnimation.removedOnCompletion = false
angleAnimation.duration = duration
angleAnimation.delegate = self
layer.addAnimation(angleAnimation, forKey: "angleAnimation")
}
第二步线条由长变短的动画
这里我们还是使用CABasicAnimation基础动画，keyPath作用于线条的strokeEnd属性，让strokeEnd从1到0来实现线条长短的动画，下面是效果图和代码：
/**
线的第一步动画，线长从长变短
*/
private func lineAnimationOne() {
let lineAnimationOne = CABasicAnimation.init(keyPath: "strokeEnd")
lineAnimationOne.duration = duration/2
lineAnimationOne.fillMode = kCAFillModeForwards
lineAnimationOne.removedOnCompletion = false
lineAnimationOne.fromValue = 1
lineAnimationOne.toValue = 0
for i in 0...3 {
let lineLayer = lines[i]
lineLayer.addAnimation(lineAnimationOne, forKey: "lineAnimationOne")
}
}
第三步线条的位移动画
这里我们也是使用CABasicAnimation基础动画，keyPath作用于线条的transform.translation.x和transform.translation.y属性，来实现向中间聚拢的效果，下面是效果图和代码：
/**
线的第二步动画，线向中间平移
*/
private func lineAnimationTwo() {
for i in 0...3 {
var keypath = "transform.translation.x"
if i%2 == 1 {
keypath = "transform.translation.y"
}
let lineAnimationTwo = CABasicAnimation.init(keyPath: keypath)
lineAnimationTwo.beginTime = CACurrentMediaTime() + duration/2
lineAnimationTwo.duration = duration/4
lineAnimationTwo.fillMode = kCAFillModeForwards
lineAnimationTwo.removedOnCompletion = false
lineAnimationTwo.autoreverses = true
lineAnimationTwo.fromValue = 0
if i < 2 {
lineAnimationTwo.toValue = lineLength/4
}else {
lineAnimationTwo.toValue = -lineLength/4
}
let lineLayer = lines[i]
lineLayer.addAnimation(lineAnimationTwo, forKey: "lineAnimationTwo")
}
//三角形两边的比例
let scale = (lineLength - 2*margin)/(lineLength - lineWidth)
for i in 0...3 {
var keypath = "transform.translation.y"
if i%2 == 1 {
keypath = "transform.translation.x"
}
let lineAnimationTwo = CABasicAnimation.init(keyPath: keypath)
lineAnimationTwo.beginTime = CACurrentMediaTime() + duration/2
lineAnimationTwo.duration = duration/4
lineAnimationTwo.fillMode = kCAFillModeForwards
lineAnimationTwo.removedOnCompletion = false
lineAnimationTwo.autoreverses = true
lineAnimationTwo.fromValue = 0
if i == 0 || i == 3 {
lineAnimationTwo.toValue = lineLength/4 * scale
}else {
lineAnimationTwo.toValue = -lineLength/4 * scale
}
let lineLayer = lines[i]
lineLayer.addAnimation(lineAnimationTwo, forKey: "lineAnimationThree")
}
}
