获取当前屏幕显示的viewcontroller

//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;

}