https://gist.github.com/db0company/369bfa43cb84b145dfd8 我对这个网站上的答案和评论做了一些测试。对我来说，以下方法有效

extension UIViewController {
    func topMostViewController() -> UIViewController {

        if let presented = self.presentedViewController {
            return presented.topMostViewController()
        }

        if let navigation = self as? UINavigationController {
            return navigation.visibleViewController?.topMostViewController() ?? navigation
        }

        if let tab = self as? UITabBarController {
            return tab.selectedViewController?.topMostViewController() ?? tab
    }

        return self
    }
}

extension UIApplication {
    func topMostViewController() -> UIViewController? {
        return self.keyWindow?.rootViewController?.topMostViewController()
    }
}

然后，通过以下方法获取top viewController:

UIApplication.shared.topMostViewController()

有这个扩展

斯威夫特2。*

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

斯威夫特3

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
    }
}

然后你可以在控制器的任何地方使用它

if let topController = UIApplication.topViewController() {
    
}

对于Swift 5+， iOS 13 +

extension UIViewController {
    static func topMostViewController() -> UIViewController? {
        if #available(iOS 13.0, *) {
            let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first
            return keyWindow?.rootViewController?.topMostViewController()
        }
        
        return UIApplication.shared.keyWindow?.rootViewController?.topMostViewController()
    }
    
    func topMostViewController() -> UIViewController? {
        if let navigationController = self as? UINavigationController {
            return navigationController.topViewController?.topMostViewController()
        }
        else if let tabBarController = self as? UITabBarController {
            if let selectedViewController = tabBarController.selectedViewController {
                return selectedViewController.topMostViewController()
            }
            return tabBarController.topMostViewController()
        }
            
        else if let presentedViewController = self.presentedViewController {
            return presentedViewController.topMostViewController()
        }
        
        else {
            return self
        }
    }
}

用法:

当你在没有UIViewController实例的情况下获取topMostViewController时

guard let viewController = UIViewController.topMostViewController() else { return }
print(viewController)

当你获取UIViewController实例的topMostViewController时

let yourVC = UIViewController()
guard let vc = yourVC.topMostViewController() else { return }
print(vc)

presentViewController显示一个视图控制器。它不会返回一个视图控制器。如果你不使用UINavigationController，你可能正在寻找presenttedviewcontroller，你需要从根开始，向下迭代所呈现的视图。

if var topController = UIApplication.sharedApplication().keyWindow?.rootViewController {
    while let presentedViewController = topController.presentedViewController {
        topController = presentedViewController
    }

    // topController should now be your topmost view controller
}

对于Swift 3+:

if var topController = UIApplication.shared.keyWindow?.rootViewController {
    while let presentedViewController = topController.presentedViewController {
        topController = presentedViewController
    }

    // topController should now be your topmost view controller
}

适用于iOS 13+

let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first

if var topController = keyWindow?.rootViewController {
    while let presentedViewController = topController.presentedViewController {
        topController = presentedViewController
    }

// topController should now be your topmost view controller
}

最简单的方法是从视图控制器堆栈中取出最后一个:

if let viewController: UIViewController = navigationController.viewControllers.last {
    // This `viewController` is on the top.
}

  var topViewController: UIViewController? {
        guard var topViewController = UIApplication.shared.keyWindow?.rootViewController else { return nil }
        while let presentedViewController = topViewController.presentedViewController {
            topViewController = presentedViewController
        }
        return topViewController
    }