Swift : self.window?.rootViewController doesn't work in AppDelegate

I want to navigate to a certain screen when the user press on the push notification. However, self.window?.rootViewController keeps on giving me error, which is Thread 1: Swift runtime failure: force unwrapped a nil value.

Now I have tried using this solution. It did work; however, it requires me to delete the SceneDelegate.swift file along with other files, and I don't want to.

func userNotificationCenter(_ center: UNUserNotificationCenter,
                                didReceive response: UNNotificationResponse,
                                withCompletionHandler completionHandler: @escaping () -> Void) {
        print("userNotificationCenter didReceive")
        defer {
            completionHandler()
        }
        guard response.actionIdentifier == UNNotificationDefaultActionIdentifier else {
            return
        }

        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let destinationVC = storyboard.instantiateViewController(withIdentifier: "MyPage") as! PageViewController

        let navigationController = self.window?.rootViewController as! UINavigationController

        navigationController.pushViewController(destinationVC, animated: false)

        UNUserNotificationCenter.current().removeAllDeliveredNotifications()
    }

Could anyone show me an alternative way to navigate to a certain when the user presses on the push notification? Thank you in advance.

You should use keyWindow instead. Try this extension:

extension UIApplication
{
    static func getKeyWindow() -> UIWindow? {
        return shared
            .connectedScenes
            .flatMap { ($0 as? UIWindowScene)?.windows ?? [] }
            .first { $0.isKeyWindow }
    }
}

and then:

let navigationController = UIApplication.getKeyWindow()?.rootViewController as! UINavigationController

navigationController.pushViewController(destinationVC, animated: false)

UNUserNotificationCenter.current().removeAllDeliveredNotifications()