iOS 13/Facebook SDK error "Unable to find a valid UIWindow"

Question

(To forestall well-intended suggestions, yes I posted this question last week on Facebook's developer forum. No responses yet.)

TL;DR

Facebook SDK 5.8 complains at startup FBSDKLog: Unable to find a valid UIWindow.

The Main Story

In a from-scratch, one-view Xcode 11/iOS 13 project, there is no longer a default UIWindow member associated with the application. (The window per se is still around; you can see it, contained in a UIWindowScene, using the View Hierarchy Debugger in Xcode, or the Reveal app.)

FBSDK 5.8 does seem to be iOS-13-aware, and looks around for it. The relevant code is at line 498 of

https://github.com/facebook/facebook-ios-sdk/blob/master/FBSDKCoreKit/FBSDKCoreKit/Internal/FBSDKInternalUtility.m.

Facebook's code iterates over the application's connectedScenes member, which for me is an empty set. How do I modify my code so that FBSDK finds the window?

Some Hacking

I tried adding the following to scene(_:willConnectTo:options:) but it seems to be too late — the FBSDKLog message has already appeared by then. (So I'm flailing...)

guard let s = (scene as? UIWindowScene) else { return }
self.window = UIWindow(windowScene: s)

The following also failed, but it was just a shot in the dark:

guard let s = (scene as? UIWindowScene) else { return }
self.window = UIWindow(frame: s.coordinateSpace.bounds)
self.window?.windowScene = s
self.window?.rootViewController = ViewController(nibName: nil, bundle: nil)
self.window?.makeKeyAndVisible()

Answer 1

If you don't use the new behaviour and don't mind reverting to the old way, you can try the following

1. Delete Application Scene Manifest key from Info.plist

   

2. Delete SceneDelegate.swift

3. Add var window: UIWindow?to AppDelegate.swift

   import UIKit
   
   @UIApplicationMain
   class AppDelegate: UIResponder, UIApplicationDelegate {
   
       var window: UIWindow? // <-- Here
   
       func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
   // Override point for customization after application launch.
   
   //        window!.makeKeyAndVisible()
   
   
       return true
       }
   
   }
   

Answer 2

1. Add window variable to AppDelegate class

   class AppDelegate: UIResponder, UIApplicationDelegate {
   
   var window: UIWindow?
   

2. Assign UIWindow inside didFinishLaunchingWithOptions

   func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
   
        window = UIWindow(frame: UIScreen.main.bounds)
        if let window = window {
            window.makeKeyAndVisible()
            self.window = window
        }
   
        ApplicationDelegate.shared.application(
             application,
             didFinishLaunchingWithOptions: launchOptions
        )
   
        return true
    }