很多答案都是不完整的。虽然这是在Objective-C中，但这是我现在能把它们放在一起的最好的编译，作为一个非递归的块:

链接到Gist，以防修改:https://gist.github.com/benguild/0d149bb3caaabea2dac3d2dca58c0816 供参考/比较的代码:

UIViewController *(^topmostViewControllerForFrontmostNormalLevelWindow)(void) = ^UIViewController *{
    // NOTE: Adapted from various stray answers here:
    //   https://stackoverflow.com/questions/6131205/iphone-how-to-find-topmost-view-controller/20515681

    UIViewController *viewController;

    for (UIWindow *window in UIApplication.sharedApplication.windows.reverseObjectEnumerator.allObjects) {
        if (window.windowLevel == UIWindowLevelNormal) {
            viewController = window.rootViewController;
            break;
        }
    }

    while (viewController != nil) {
        if ([viewController isKindOfClass:[UITabBarController class]]) {
            viewController = ((UITabBarController *)viewController).selectedViewController;
        } else if ([viewController isKindOfClass:[UINavigationController class]]) {
            viewController = ((UINavigationController *)viewController).visibleViewController;
        } else if (viewController.presentedViewController != nil && !viewController.presentedViewController.isBeingDismissed) {
            viewController = viewController.presentedViewController;
        } else if (viewController.childViewControllers.count > 0) {
            viewController = viewController.childViewControllers.lastObject;
        } else {
            BOOL repeat = NO;

            for (UIView *view in viewController.view.subviews.reverseObjectEnumerator.allObjects) {
                if ([view.nextResponder isKindOfClass:[UIViewController class]]) {
                    viewController = (UIViewController *)view.nextResponder;

                    repeat = YES;
                    break;
                }
            }

            if (!repeat) {
                break;
            }
        }
    }

    return viewController;
};

最新Swift版本: 创建一个文件，命名为UIWindowExtension.swift，并粘贴以下代码片段:

import UIKit

public extension UIWindow {
    public var visibleViewController: UIViewController? {
        return UIWindow.getVisibleViewControllerFrom(self.rootViewController)
    }

    public static func getVisibleViewControllerFrom(_ vc: UIViewController?) -> UIViewController? {
        if let nc = vc as? UINavigationController {
            return UIWindow.getVisibleViewControllerFrom(nc.visibleViewController)
        } else if let tc = vc as? UITabBarController {
            return UIWindow.getVisibleViewControllerFrom(tc.selectedViewController)
        } else {
            if let pvc = vc?.presentedViewController {
                return UIWindow.getVisibleViewControllerFrom(pvc)
            } else {
                return vc
            }
        }
    }
}

func getTopViewController() -> UIViewController? {
    let appDelegate = UIApplication.shared.delegate
    if let window = appDelegate!.window {
        return window?.visibleViewController
    }
    return nil
}

可以在任何地方使用:

if let topVC = getTopViewController() {

}

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
    }

一个完整的非递归版本，照顾到不同的场景:

视图控制器正在呈现另一个视图 视图控制器是一个UINavigationController 视图控制器是一个UITabBarController

objective - c

 UIViewController *topViewController = self.window.rootViewController;
 while (true)
 {
     if (topViewController.presentedViewController) {
         topViewController = topViewController.presentedViewController;
     } else if ([topViewController isKindOfClass:[UINavigationController class]]) {
         UINavigationController *nav = (UINavigationController *)topViewController;
         topViewController = nav.topViewController;
     } else if ([topViewController isKindOfClass:[UITabBarController class]]) {
         UITabBarController *tab = (UITabBarController *)topViewController;
         topViewController = tab.selectedViewController;
     } else {
         break;
     }
 }

斯威夫特 4+

extension UIWindow {
    func topViewController() -> UIViewController? {
        var top = self.rootViewController
        while true {
            if let presented = top?.presentedViewController {
                top = presented
            } else if let nav = top as? UINavigationController {
                top = nav.visibleViewController
            } else if let tab = top as? UITabBarController {
                top = tab.selectedViewController
            } else {
                break
            }
        }
        return top
    }
}

为了完成Eric的回答(谁省略了弹出窗口，导航控制器，选项卡控制器，视图控制器添加为子视图到一些其他的视图控制器遍历)，这是我的版本返回当前可见的视图控制器:

=====================================================================

- (UIViewController*)topViewController {
    return [self topViewControllerWithRootViewController:[UIApplication sharedApplication].keyWindow.rootViewController];
}

- (UIViewController*)topViewControllerWithRootViewController:(UIViewController*)viewController {
    if ([viewController isKindOfClass:[UITabBarController class]]) {
        UITabBarController* tabBarController = (UITabBarController*)viewController;
        return [self topViewControllerWithRootViewController:tabBarController.selectedViewController];
    } else if ([viewController isKindOfClass:[UINavigationController class]]) {
        UINavigationController* navContObj = (UINavigationController*)viewController;
        return [self topViewControllerWithRootViewController:navContObj.visibleViewController];
    } else if (viewController.presentedViewController && !viewController.presentedViewController.isBeingDismissed) {
        UIViewController* presentedViewController = viewController.presentedViewController;
        return [self topViewControllerWithRootViewController:presentedViewController];
    }
    else {
        for (UIView *view in [viewController.view subviews])
        {
            id subViewController = [view nextResponder];
            if ( subViewController && [subViewController isKindOfClass:[UIViewController class]])
            {
                if ([(UIViewController *)subViewController presentedViewController]  && ![subViewController presentedViewController].isBeingDismissed) {
                    return [self topViewControllerWithRootViewController:[(UIViewController *)subViewController presentedViewController]];
                }
            }
        }
        return viewController;
    }
}

=====================================================================

现在你需要做的就是像下面这样调用上面的方法:

UIViewController *topMostViewControllerObj = [self topViewController];

iOS 4在UIWindow上引入了rootViewController属性:

[UIApplication sharedApplication].keyWindow.rootViewController;

你需要在创建视图控制器后自己设置。