模仿苹果做了一个全局浮动按钮，可以拖拽，可以展开和收缩，自动靠边。实现步骤如下：
1.继承自UIView，重写init方法，在init里添加点击手势和拖动手势。加到appDelegate.window!里，实现全局浮动。
2.定制按钮样式，通过layer层画出五个嵌套的圆。
let layer = CAShapeLayer()
layer.path = path.cgPath
layer.fillColor = UIColor(white: CGFloat(white), alpha: CGFloat(alpha)).cgColor
layer.strokeColor = UIColor(white: CGFloat(white), alpha: CGFloat(alpha)).cgColor
self.layer.addSublayer(layer)
3.实现拖拽手势效果：
switch pan.state {
case UIGestureRecognizerState.began:
self.superview?.bringSubview(toFront: self) //拖拽开始
break
case UIGestureRecognizerState.changed:
let point = pan.translation(in: self)
let f = self.frame
let dx = point.x + f.origin.x
let dy = point.y + f.origin.y
self.frame = CGRect(x: dx, y: dy, width: LYCopyGlobalButton.ButtonSize, height: LYCopyGlobalButton.ButtonSize)//跟随手势完成拖拽效果
// 注意一旦你完成上述的移动，将translation重置为0十分重要。否则translation每次都会叠加
pan.setTranslation(CGPoint(x: 0, y: 0), in: self)
break
case UIGestureRecognizerState.ended:
let f = self.frame//拖拽结束，需要靠边
var dx = f.origin.x
var dy = f.origin.y
if dx > superFrame.size.width-10-LYCopyGlobalButton.ButtonSize {
dx = superFrame.size.width-10-LYCopyGlobalButton.ButtonSize
} else if dx < 10 {
dx = 10.0
} else {
dx = dx > superFrame.size.width-dx ? superFrame.size.width-10-LYCopyGlobalButton.ButtonSize : 10
}
if dy > superFrame.size.height-10-LYCopyGlobalButton.ButtonSize {
dy = superFrame.size.height-10-LYCopyGlobalButton.ButtonSize
} else if dy < 10 {
dy = 10.0
}//永远靠左右两边，不用管上下
UIView.animate(withDuration: 0.2) {
self.frame = CGRect(x: dx, y: dy, width: f.size.width, height: f.size.height)
}
break
default: break
}
let point:CGPoint = pan.translation(in: self)
self.transform = CGAffineTransform.init(translationX: point.x, y: point.y)
4.通过动画效果实现展开缩放效果。
附上代码地址：点击打开链接获取swift代码