Need Docs for Using Airplay as 2nd Screen (not mirroring)

1. Let the user choose the screen with AVRoutePickerView.

2. After the user has chosen the screen, set up a new UIWindow object for the corresponding UIScreen (see section "Handling Screen Connection and Disconnection Notifications" https://developer.apple.com/documentation/uikit/uiscreen)

3. Create a view controller for your content and set it as the UIWindow's rootViewController.

Thanks for the links. They were helpful, but not complete.

I've got an AVRoutePickerView on my screen, and I added an observer to the NotificationCenter (as directed in the documentation). However, when I choose the AppleTV from the view picker, I get the following error message:

MPMediaControlsRemoteViewController Dismissing because view service terminated

I was unable to find anything in a Google search regarding a cause/solution for that message.

However, if I first mirror my iPhone to the AppleTV before launching my app, the observer method does get fired, and I can see the 2nd screen. That's definitely further than I had gotten before, but I'd like to know how to get the AVRoutePickerView observer to work properly. Here are the pertinent parts of my code (a SpriteKit game), in case it is needed for reference:

GameViewController:

override func viewDidLoad() {
    super.viewDidLoad()

    let notifier = NotificationCenter.default
    notifier.addObserver(self, selector: #selector(GameViewController.screenDidConnect), name: NSNotification.Name.UIScreenDidConnect, object: nil)
    notifier.addObserver(self, selector: #selector(GameViewController.screenDidDisconnect), name: NSNotification.Name.UIScreenDidDisconnect, object: nil)

    let skView = self.view as! SKView
    let scene = TitleScene(size: (skView.bounds.size)!)
    scene.backgroundColor = SKColor.black
    skView.presentScene(scene)
}

@objc fileprivate func screenDidConnect(notification: NSNotification) {
    print("GameViewController: Screen was connected: \n\(notification)")
    print("# of Screens: \(UIScreen.screens.count)")
}
   
@objc fileprivate func screenDidDisconnect(notification: NSNotification) {
    print("GameViewController: Screen was disconnected: \n\(notification)")
    print("# of Screens: \(UIScreen.screens.count)")
}

Any ideas as to what I'm missing?