Swift 中添加的UIView都是有层级的. 我们先添加三个看一看 let view1=UIView(frame: CGRectMake(10, 50, 200, 200)) let view2=UIView(frame: CGRectMake(60, 100, 200, 200)) let view3=UIView(frame: CGRectMake(110, 150, 200, 200)) view1.backgroundColor=UIColor.redColor() view2.bac