在一般应用中，我们使用 addSubview 方法是添加到当前控制器 ViewController 上的，但是对于某些情况下，我们需要把视图添加到顶层控制器视图上，即要获取顶层视图控制器。

• 当前顶层窗口

    
    //UIWindow *window = [[UIApplication sharedApplication].windows lastObject];
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    // 添加到窗口
    [window addSubview:testView];

• 获取View父视图

- (UIViewController )viewController
{
    for (UIView next = [self superview]; next; next = next.superview) {
        UIResponder *nextResponder = [next nextResponder];
        if ([nextResponder isKindOfClass:[UIViewController class]]) {
            return (UIViewController *)nextResponder;
        }
    }
    return nil;
}

• 获取最上层控制器|当前控制器

//获取当前最上层的控制器
-(UIViewController *) getTopOrCurrentViewController
{
    UIWindow *topWindow = [UIApplication sharedApplication].keyWindow;
    if (topWindow.windowLevel != UIWindowLevelNormal)
    {
        topWindow = [self returnWindowWithWindowLevelNormal];
    }
    
    UIViewController *topController = topWindow.rootViewController;
    if(topController == nil)
    {
        topWindow = [UIApplication sharedApplication].delegate.window;
        if (topWindow.windowLevel != UIWindowLevelNormal)
        {
            topWindow = [self returnWindowWithWindowLevelNormal];
        }
        topController = topWindow.rootViewController;
    }
    
    while(topController.presentedViewController)
    {
        topController = topController.presentedViewController;
    }
    
    if([topController isKindOfClass:[UINavigationController class]])
    {
        UINavigationController *nav = (UINavigationController*)topController;
        topController = [nav.viewControllers lastObject];
        
        while(topController.presentedViewController)
        {
            topController = topController.presentedViewController;
        }
    }
    
    return topController;
}

-(UIWindow *) returnWindowWithWindowLevelNormal
{
    NSArray *windows = [UIApplication sharedApplication].windows;
    for(UIWindow *topWindow in windows)
    {
        if (topWindow.windowLevel == UIWindowLevelNormal)
            return topWindow;
    }
    return [UIApplication sharedApplication].keyWindow;
}