现在来看看View的生命周期
显示过程
-(void)willMoveToSuperview:(UIView *)newSuperview
-(void)didMoveToSuperview
-(void)willMoveToWindow:(UIWindow *)newWindow
-(void)didMoveToWindow
-(void)layoutSubviews
移除过程
-(void)willMoveToSuperview:(UIView *)newSuperview
-(void)willMoveToWindow:(UIWindow *)newWindow
-(void)didMoveToWindow
-(void)didMoveToSuperview
-(void)dealloc