不确定这是否会帮助你通过找到最顶层的视图控制器来实现，但我试图呈现一个新的视图控制器，但如果我的根视图控制器已经有一个模态对话框，它会被阻塞，所以我将循环到所有模态视图控制器的顶部使用以下代码:

UIViewController* parentController =[UIApplication sharedApplication].keyWindow.rootViewController;

while( parentController.presentedViewController &&
       parentController != parentController.presentedViewController )
{
    parentController = parentController.presentedViewController;
}

另一个解决方案依赖于responder链，它可能工作，也可能不工作，这取决于第一个responder是什么:

获取第一个响应器。 获取与第一个responder相关联的UIViewController。

示例伪代码:

+ (UIViewController *)currentViewController {
    UIView *firstResponder = [self firstResponder]; // from the first link above, but not guaranteed to return a UIView, so this should be handled more appropriately.
    UIViewController *viewController = [firstResponder viewController]; // from the second link above
    return viewController;
}

这是一个Swift的应用程序的实现与UINavigationController的根。

  if let nav = UIApplication.sharedApplication().keyWindow?.rootViewController as? UINavigationController{
        //get the current's navigation view controller
        var vc = nav.topViewController
        while vc?.presentedViewController != nil {
            vc = vc?.presentedViewController
        }
        return vc
    }

这是对Eric的回答的改进:

UIViewController *_topMostController(UIViewController *cont) {
    UIViewController *topController = cont;

    while (topController.presentedViewController) {
        topController = topController.presentedViewController;
    }

    if ([topController isKindOfClass:[UINavigationController class]]) {
        UIViewController *visible = ((UINavigationController *)topController).visibleViewController;
        if (visible) {
            topController = visible;
        }
    }

    return (topController != cont ? topController : nil);
}

UIViewController *topMostController() {
    UIViewController *topController = [UIApplication sharedApplication].keyWindow.rootViewController;

    UIViewController *next = nil;

    while ((next = _topMostController(topController)) != nil) {
        topController = next;
    }

    return topController;
}

UIViewController *cont是一个辅助函数。

现在你所需要做的就是调用topMostController()和最顶端的UIViewController应该被返回!

这个答案包含了childViewControllers，并维护了一个干净易读的实现。

+ (UIViewController *)topViewController
{
    UIViewController *rootViewController = [UIApplication sharedApplication].keyWindow.rootViewController;

    return [rootViewController topVisibleViewController];
}

- (UIViewController *)topVisibleViewController
{
    if ([self isKindOfClass:[UITabBarController class]])
    {
        UITabBarController *tabBarController = (UITabBarController *)self;
        return [tabBarController.selectedViewController topVisibleViewController];
    }
    else if ([self isKindOfClass:[UINavigationController class]])
    {
        UINavigationController *navigationController = (UINavigationController *)self;
        return [navigationController.visibleViewController topVisibleViewController];
    }
    else if (self.presentedViewController)
    {
        return [self.presentedViewController topVisibleViewController];
    }
    else if (self.childViewControllers.count > 0)
    {
        return [self.childViewControllers.lastObject topVisibleViewController];
    }

    return self;
}

迅速:

extension UIWindow {

func visibleViewController() -> UIViewController? {
    if let rootViewController: UIViewController  = self.rootViewController {
        return UIWindow.getVisibleViewControllerFrom(rootViewController)
    }
    return nil
}

class func getVisibleViewControllerFrom(vc:UIViewController) -> UIViewController {
if vc.isKindOfClass(UINavigationController.self) {

    let navigationController = vc as UINavigationController
    return UIWindow.getVisibleViewControllerFrom( navigationController.visibleViewController)

} else if vc.isKindOfClass(UITabBarController.self) {

    let tabBarController = vc as UITabBarController
    return UIWindow.getVisibleViewControllerFrom(tabBarController.selectedViewController!)

} else {

    if let presentedViewController = vc.presentedViewController {

        return UIWindow.getVisibleViewControllerFrom(presentedViewController.presentedViewController!)

    } else {

        return vc;
    }
}
}

用法:

 if let topController = window.visibleViewController() {
            println(topController)
        }