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() {
    
}

iOS13+ //top最多视图控制器

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 UIWindow.key!.rootViewController?.topMostViewController()
    }
}

extension UIWindow {
    static var key: UIWindow? {
        if #available(iOS 13, *) {
            return UIApplication.shared.windows.first { $0.isKeyWindow }
        } else {
            return UIApplication.shared.keyWindow
        }
    }
}

//use let vc = UIApplication.shared.topMostViewController()

// End top Most view Controller

@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
}

    extension UIApplication {
        
       public var mainKeyWindow: UIWindow? {
           if #available(iOS 13, *) {
             return UIApplication.shared.connectedScenes
            .filter { $0.activationState == .foregroundActive }
            .first(where: { $0 is UIWindowScene })
            .flatMap { $0 as? UIWindowScene }?.windows
            .first(where: \.isKeyWindow)
           } else {
              return UIApplication.shared.windows.first { $0.isKeyWindow }
           }
        }
    

    public var rootViewController: UIViewController? {
        guard let keyWindow = UIApplication.shared.mainKeyWindow, let rootViewController = keyWindow.rootViewController else {
            return nil
        }
        return rootViewController
    }

    public func topViewController(controller: UIViewController? = UIApplication.shared.rootViewController) -> UIViewController? {

        if controller == nil {
            return topViewController(controller: rootViewController)
        }
        
        if let navigationController = controller as? UINavigationController {
            return topViewController(controller: navigationController.visibleViewController)
        }

        if let tabController = controller as? UITabBarController {
            if let selectedViewController = tabController.selectedViewController {
                return topViewController(controller: selectedViewController)
            }
        }

        if let presentedViewController = controller?.presentedViewController {
            return topViewController(controller: presentedViewController)
        }

        return controller
    }
}

Swift 5.2及以上版本

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.
}

斯威夫特 5+

声明

func topViewController() -> 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
        
    }
    
}

Use

topViewController()?.view.addSubview(UIView())