//点击屏幕的事件           override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {               //自定义动画效果               func anim(){                   img1.alpha=0.1                   img1.center=CGPoint(x: 0.0, y: 0.0)               }               func completion(v:Bool){                   println("anim completion\(v):\(falg)")               }                              UIView.transitionWithView(img1, duration: 1.0, options: UIViewAnimationOptions.TransitionNone, animations: anim, completion: completion)                                               //视图动画效果 3步  1：开始动画 2:配置动画  3:提交动画                 UIView.beginAnimations(nil, context: nil)                 UIView.setAnimationTransition(UIViewAnimationTransition.CurlDown, forView: img1, cache: true)                 UIView.setAnimationDuration(1.0)                 UIView.commitAnimations()                                             //视图的切换                              if falg{                   falg=false                   /*视图切换                  fromView 开始视图                  toView 结束视图                  duration 效果时间                  options 动画效果模式                  completion 回调方法                  */                   UIView.transitionFromView(img2, toView: img1, duration: 1.0, options: UIViewAnimationOptions.TransitionFlipFromRight, completion: completion)               }else{                   falg=true                   UIView.transitionFromView(img1, toView: img2, duration: 1.0, options: UIViewAnimationOptions.TransitionFlipFromLeft, completion: completion)               }                          }