最近在看IOS动画相关的东西，正好看到京东收藏商品的时候有个心跳的动画，于是研究了一下，代码很简单
let heart = UIButton(frame: CGRect(x: APP_FRAME_WIDTH*0.5-25, y: 200, width: 50, height: 50))
self.view.addSubview(heart)
heart.setImage(UIImage(named: "heart") , for: .normal)
heart.setImage(UIImage(named: "hearted") , for: .selected)
heart.addTarget(self, action: #selector(ViewController.click(_:)), for: .touchUpInside)
点击事件：
button.isSelected = !button.isSelected
let k = CAKeyframeAnimation.init(keyPath: "transform.scale")
k.values = [0.1,1.0,1.5]
k.keyTimes = [0.0,0.8,1.0]
k.calculationMode = kCAAnimationLinear
button.layer.add(k, forKey: "SHOW")
