在SWIFT 5.2中

你可以使用下面的代码:

import UIKit

extension UIWindow {
    static func getTopViewController() -> UIViewController? {
        if #available(iOS 13, *){
            let keyWindow = UIApplication.shared.windows.filter {$0.isKeyWindow}.first
            
            if var topController = keyWindow?.rootViewController {
                while let presentedViewController = topController.presentedViewController {
                    topController = presentedViewController
                }
                return topController
            }
        } else {
            if var topController = UIApplication.shared.keyWindow?.rootViewController {
                while let presentedViewController = topController.presentedViewController {
                    topController = presentedViewController
                }
                return topController
            }
        }
        return nil
    }
}

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() {
    
}

extension UIWindow {

    func visibleViewController() -> UIViewController? {
        if let rootViewController: UIViewController = self.rootViewController {
            return UIWindow.getVisibleViewControllerFrom(vc: rootViewController)
        }
        return nil
    }

    static func getVisibleViewControllerFrom(vc:UIViewController) -> UIViewController {
        if let navigationController = vc as? UINavigationController,
            let visibleController = navigationController.visibleViewController  {
            return UIWindow.getVisibleViewControllerFrom( vc: visibleController )
        } else if let tabBarController = vc as? UITabBarController,
            let selectedTabController = tabBarController.selectedViewController {
            return UIWindow.getVisibleViewControllerFrom(vc: selectedTabController )
        } else {
            if let presentedViewController = vc.presentedViewController {
                return UIWindow.getVisibleViewControllerFrom(vc: presentedViewController)
            } else {
                return vc
            }
        }
    }
}

用法:

if let topController = window.visibleViewController() {
    println(topController)
}

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
        }
    }
}

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
}

我喜欢@dianz的回答，下面是swift 3的版本。它基本上是一样的，但他少了一个大括号，一些语法/变量/方法名已经改变了。所以它就在这里!

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

用法仍然是一样的:

if let topController = UIApplication.topViewController() {
    print("The view controller you're looking at is: \(topController)")
}