实现思路：
- 重写init方法，添加点击事件
override init(frame: CGRect) {
super.init(frame: frame)
self.addTarget(self, action: #selector(self.touchedDown(sender:events:)), for: UIControlEvents.touchUpInside)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
fatalError("")
} - 根据点击事件创建点击事件类，放进字典中。
@objc func touchedDown(sender: LYWaveTouchButton, events: UIEvent) {
let touch = events.touches(for: sender)?.first
let point = touch?.location(in: sender)//以button为坐标系
let buttonCircle: LYButtonCircle = LYButtonCircle()//点击事件类
buttonCircle.circleCenterX = (point?.x)!//圆心
buttonCircle.circleCenterY = (point?.y)!
buttonCircle.circleRait = 0.0//初始半径
//以button中点为基准，判断最大半径值
let maxX = point!.x > (self.frame.size.width - point!.x) ? point!.x : (self.frame.size.width - point!.x)
let maxY = point!.y > (self.frame.size.height - point!.y) ? point!.y : (self.frame.size.height - point!.y)
buttonCircle.circleWidth = maxX > maxY ? maxX : maxY
circles[circleFlag] = buttonCircle
//为每个点击事件增加一个定时器,每隔0.01s画一个半径不断增大的圆
Timer.scheduledTimer(timeInterval: TimeInterval(0.01), target: self, selector: #selector(self.timerFunction(timer:)), userInfo: circleFlag, repeats: true)
circleFlag += 1
} - 每增加一个点击事件就开一个定时器，重复画以点击事件为圆心半径不断增大的圆。直到圆超出button。
@objc func timerFunction(timer: Timer) {
self.setNeedsDisplay()//会调用自动调用drawRect方法，这样可以拿到UIGraphicsGetCurrentContext，就可以画画了
let index:Int = timer.userInfo! as! Int
let buttonCircle: LYButtonCircle = circles[index]!
//circleRait：半径缩放系数，circleRait若等于1则圆达到最大半径，字典中删除点击事件，结束定时任务
if buttonCircle.circleRait <= 1 {
buttonCircle.circleRait += 1.0/CGFloat(self.loopCount)
} else {
circles.removeValue(forKey: index)
timer.invalidate()
}
}
override func draw(_ rect: CGRect) {
let context: CGContext = UIGraphicsGetCurrentContext()!
let endAngel = CGFloat(Double.pi * 2)
for buttonCircle: LYButtonCircle in circles.values {
//画圆
context.addArc(center: CGPoint(x: buttonCircle.circleCenterX, y: buttonCircle.circleCenterY), radius: buttonCircle.circleRait*buttonCircle.circleWidth, startAngle:0, endAngle: endAngel, clockwise: false)
self.hightLightColor.withAlphaComponent(1-buttonCircle.circleRait).setStroke()
self.hightLightColor.withAlphaComponent(1-buttonCircle.circleRait).setFill()
context.fillPath()
}
}
附上代码地址：点击打开链接获取swift代码