1 Reply
      Latest reply on Oct 21, 2019 4:52 PM by ben_singaccord
      ben_singaccord Level 1 Level 1 (0 points)

        I'm trying to implement scene-based state restoration in an iPad OS 13 / macCatalyst app.


        The docs say .stateRestorationActivity might be nil in scene(_:, willConnectTo:, options:) if data protection is turned on.


        I don't have data protection turned on in my macCatalyst app, but .stateRestorationActivity is always nil, despite my verifying that stateRestorationActivity(for scene: UIScene) -> NSUserActivity? is returning a non-nil activity with an identifier that's set up in my Info.plist and has the target content identifier:

        class DocumentViewContoller : UIViewController {
        override func viewDidAppear(_ animated: Bool) {
          let activity = NSUserActivity.newShowActivity()     //extension creates this with correct activityType string
          activity.targetContentIdentifier = document?.fileURL.absoluteString
          activity.title = document?.fileURL.lastPathComponent
          view.window?.windowScene?.userActivity = activity
          guard isViewLoaded
          ,let activationConditions = view.window?.windowScene?.activationConditions
          else { return }
          guard let url = document?.fileURL else {
          activationConditions.canActivateForTargetContentIdentifierPredicate = NSPredicate(value: true)
          activationConditions.prefersToActivateForTargetContentIdentifierPredicate = NSPredicate(value: false)
          return }
          activationConditions.canActivateForTargetContentIdentifierPredicate = NSPredicate(format: "self == '\(url.absoluteString)'")
          activationConditions.prefersToActivateForTargetContentIdentifierPredicate = NSPredicate(format: "self == '\(url.absoluteString)'")
        // activity.becomeCurrent()

        and I verified that the predicates were set on the scene in stateRestorationActivity(for scene:)


        What other conditions do I have to meet in order that my scenes are restored when the app launches again?


        If it will always be nil, why did the WWDC presenters, in 3 separate talks, tell us we should look for it in that method?

        If it will always be nil in this method, during which delegate callback method should I expect it to be non-nil?

        It it will always be nil in all delegate callbacks, then how do I get an app to re-open document scenes which were open when the app was last quit?