之前的答案似乎不能处理rootController是UITabBarController或UINavigationController的情况。

下面是swift中适用于这些情况的函数:

func getCurrentView() -> UIViewController?
{
    if let window = UIApplication.sharedApplication().keyWindow, var currentView: UIViewController = window.rootViewController
    {
        while (currentView.presentedViewController != nil)
        {
            if let presented = currentView.presentedViewController
            {
                currentView = presented
            }
        }

        if currentView is UITabBarController
        {
            if let visible = (currentView as! UITabBarController).selectedViewController
            {
                currentView = visible;
            }
        }

        if currentView is UINavigationController
        {
            if let visible = (currentView as! UINavigationController).visibleViewController
            {
                currentView = visible;
            }
        }

        return currentView
    }

    return nil
}

我最近在我的一个项目中遇到了这种情况，当网络状态发生变化时，需要显示一个通知视图，无论显示的控制器是什么，无论类型是什么(UINavigationController，经典控制器或自定义视图控制器)。

所以我刚刚发布了我的代码，这很简单，实际上是基于一个协议，所以它对每种类型的容器控制器都是灵活的。 它似乎与上一个答案有关，但方式更加灵活。

你可以从这里获取代码:PPTopMostController

并得到最顶级的控制器使用

UIViewController *c = [UIViewController topMostController];

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;
}

我认为大多数答案都完全忽略了UINavigationViewController，所以我用下面的实现来处理这个用例。

+ (UIViewController *)topMostController {
    UIViewController * topController = [UIApplication sharedApplication].keyWindow.rootViewController;
    while (topController.presentedViewController || [topController isMemberOfClass:[UINavigationController class]]) {
        if([topController isMemberOfClass:[UINavigationController class]]) {
            topController = [topController childViewControllers].lastObject;
        } else {
            topController = topController.presentedViewController;
        }
    }

    return topController;
}

Swift 4.2扩展

extension UIApplication {

    class func topViewController(controller: UIViewController? = UIApplication.shared.keyWindow?.rootViewController) -> UIViewController? {
        if let navigationController = controller as? UINavigationController {
            return topViewController(controller: navigationController.visibleViewController)
        }
        if let tabController = controller as? UITabBarController {
            if let selected = tabController.selectedViewController {
                return topViewController(controller: selected)
            }
        }
        if let presented = controller?.presentedViewController {


            return topViewController(controller: presented)
        }
        return controller
    }
}

在任何地方都可以使用，

 UIApplication.topViewController()?.present(yourController, animated: true, completion: nil)

或者像,

 UIApplication.topViewController()?
                    .navigationController?
                    .popToViewController(yourController,
                                         animated: true)

适合任何类，如UINavigationController, UITabBarController

享受吧!

另一个Swift解决方案

func topController() -> UIViewController? {

    // recursive follow
    func follow(from:UIViewController?) -> UIViewController? {
        if let to = (from as? UITabBarController)?.selectedViewController {
            return follow(to)
        } else if let to = (from as? UINavigationController)?.visibleViewController {
            return follow(to)
        } else if let to = from?.presentedViewController {
            return follow(to)
        }
        return from
    }

    let root = UIApplication.sharedApplication().keyWindow?.rootViewController

    return follow(root)

}