获取最顶层的 UIViewController

我似乎无法到达最顶端UIViewController无法访问UINavigationController。这是我到目前为止所拥有的：

UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(vc, animated: true, completion: nil)

然而，它似乎没有做任何事情。这keyWindow and rootViewController似乎也是非零值，所以可选链不应该成为问题。

NOTE: 做这样的事情是一个坏主意。它打破了 MVC 模式。

presentViewController显示视图控制器。它不返回视图控制器。如果您没有使用UINavigationController，您可能正在寻找presentedViewController您需要从根开始并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
}