Question

这是一个UIViewController，其中创建了UINavigationController：

class Main_ProfileViewController: UIViewController { 

    var ProfileNavigationController = UINavigationController()

    buildProfileNavigationController()

    func buildProfileNavigationController() {
        let RootViewController = BlankViewController200()
        ProfileNavigationController = UINavigationController(rootViewController: RootViewController)
        self.view.addSubview(ProfileNavigationController.view)
    }

}

这是带有导航控制器委托的主容器类，以获取当前堆栈的顶部：

class MainContainerViewController: UIViewController {

    var currentTop: UIViewController?

}

extension MainContainerViewController: UINavigationControllerDelegate {

    func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
        currentTop = viewController
        print(currentTop)
    }

}

但是，没有任何内容打印到控制台。这是如何实现的？

Answer 1

要获得top viewController，您可以使用以下代码：

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
    }
}

如何从UINavigationController获取当前堆栈的顶部？

1 个答案: