//获取当前屏幕显示的viewcontroller

- (UIViewController *)getCurrentVC  
{  
    UIViewController *result = nil;  
      
    UIWindow * window = [[UIApplication sharedApplication] keyWindow];  
    if (window.windowLevel != UIWindowLevelNormal)  
    {  
        NSArray *windows = [[UIApplication sharedApplication] windows];  
        for(UIWindow * tmpWin in windows)  
        {  
            if (tmpWin.windowLevel == UIWindowLevelNormal)  
            {  
                window = tmpWin;  
                break;  
            }  
        }  
    }  
      
    UIView *frontView = [[window subviews] objectAtIndex:0];  
    id nextResponder = [frontView nextResponder];  
      
    if ([nextResponder isKindOfClass:[UIViewController class]])  
        result = nextResponder;  
    else  
        result = window.rootViewController;  
      
    return result;  
}