例如要获取的控件是Lable, 则可使用下面方法获取该视图相对屏幕的位置:
UIWindow * window=[[[UIApplication sharedApplication] delegate] window];
CGRect startRact = [Lable convertRect:Lable.bounds toView:window];
UIWindow * window=[[[UIApplication sharedApplication] delegate] window];
CGRect startRact = [Lable convertRect:Lable.bounds toView:window];