如何在iPadOS多窗口(SceneDelegate)中获得rootViewController?

问题描述

我正在使用Xcode 11(beta3)并为iOS 13构建应用程序.在我的项目中，我创建了UIWindowSceneDelegate的委托方法，以在Info.plist中声明它.现在，我可以创建多个窗口(和UIScene).

I am using Xcode 11 (beta3) and building an app for iOS 13. In my project I created the delegate methods for UIWindowSceneDelegate declaring it in Info.plist.Now I'm able to create multiple windows (and UIScene).

现在我已经没有一个窗口了，如何访问rootViewController?我需要它来获取对它所持有的对象和范围的一些引用.

How can I access the rootViewController now I've not anymore a single window? I need it to get some reference to objects and bounds it holds.

在我的AppDelegate window is nil和ViewController(子视图控制器)实例中，我尝试使用self.view.window.rootViewController，但是我发现viewDidLoad()为时过早(我认为)，并且窗口仍然为零，在viewDidAppear()，但是我不需要在每次视图控制器出现时都执行此过程.

In my AppDelegate window is nil, and in my ViewController (child view controller) instance I tried using self.view.window.rootViewController but I found out that viewDidLoad() is too soon (I think) and the window is still nil, works in viewDidAppear(), but I don't need to make this process every time the view controller appears.

这种处理应用程序场景的新方法的最佳实践是什么?

What's the best practice with this new way to handle application scenes?

这是我的AppDelegate:

Here is my AppDelegate:

func application(_ application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? = nil) -> Bool {
        return true
    }

    func application(_ application: UIApplication,
                     configurationForConnecting connectingSceneSession: UISceneSession,
                     options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }

我的SceneDelegate:

My SceneDelegate:

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // yes it's empty, I'm using storyboard
    }

推荐答案

现在，您有多个rootViewController，每个场景一个.首先，您必须回答使用时需要的那个.

Now you have more than one rootViewController, one for each scene.First, you have to answer which one you need at the moment of usage.

可能您想获取当前活动场景的rootViewController之一，则可以使用以下方法:

Probably you want to get one of the rootViewController of the currently active scene then you can use this:

        var rootVC:UIViewController? = nil
        if #available(iOS 13.0, *) {
            for scene in UIApplication.shared.connectedScenes {
                if scene.activationState == .foregroundActive {
                    rootVC = ((scene as? UIWindowScene)!.delegate as! UIWindowSceneDelegate).window!!.rootViewController
                    break
                }
            }
        } else {
            // Fallback on earlier versions
        }

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