1，UIWindow *window = [UIApplication sharedApplication].keyWindow;   // 獲得根窗口 2.   - (UIView *)rootView {          UIView *rootView = self;     while (rootView.superview) {       if ([rootView.superview isKindOfClass:[UIWindow class]]) {         break;       }       rootView = rootView.superview;     }     return rootView;   }