extension UIViewController {
    func topMostViewController() -> UIViewController {
        if self.presentedViewController == nil {
            return self
        }
        if let navigation = self.presentedViewController as? UINavigationController {
            return navigation.visibleViewController.topMostViewController()
        }
        if let tab = self.presentedViewController as? UITabBarController {
            if let selectedTab = tab.selectedViewController {
                return selectedTab.topMostViewController()
            }
            return tab.topMostViewController()
        }
        return self.presentedViewController!.topMostViewController()
    }
}

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

你可以在AppDelegate中定义一个UIViewController变量，并在每个viewWillAppear中设置这个变量为self。(然而，dianz的答案是最好的答案。)

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    let appDel = UIApplication.sharedApplication().delegate as! AppDelegate
    appDel.currentVC = self
}

对于任何寻求快速5/iOS 13+解决方案的人(keywindow自iOS 13以来已弃用)

extension UIApplication {

    class func getTopMostViewController() -> UIViewController? {
        let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first
        if var topController = keyWindow?.rootViewController {
            while let presentedViewController = topController.presentedViewController {
                topController = presentedViewController
            }
            return topController
        } else {
            return nil
        }
    }
}

@AlberZou略有变化，使用计算变量而不是函数

extension UIViewController {
  var 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 {
  var topMostViewController : UIViewController? {
    return self.keyWindow?.rootViewController?.topMostViewController
  }
}

然后说

if let topViewControler = UIApplication.shared.topMostViewController {
    ... do stuff
}

太多口味了，但都不是一种反复精心制作的。结合前面的内容:

     func topMostController() -> UIViewController? {
        var from = UIApplication.shared.keyWindow?.rootViewController
        while (from != nil) {
            if let to = (from as? UITabBarController)?.selectedViewController {
                from = to
            } else if let to = (from as? UINavigationController)?.visibleViewController {
                from = to
            } else if let to = from?.presentedViewController {
                from = to
            } else {
                break
            }
        }
        return from
    }

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()