Title: Unable to Retrieve APNs Token in Flutter macOS App

Question:

I’m developing a Flutter macOS application and am trying to retrieve the APNs token using the Firebase Messaging plugin. Despite implementing the necessary code, I always receive null when trying to fetch the APNs token. Here’s a detailed description of my setup and issue:

Native Code (Swift)

import Cocoa
import FlutterMacOS
import UserNotifications

@main
class AppDelegate: FlutterAppDelegate, UNUserNotificationCenterDelegate {

    override func applicationDidFinishLaunching(_ notification: Notification) {
        super.applicationDidFinishLaunching(notification)

        // Register for push notifications
        registerForPushNotifications()

        // Setup Flutter messaging
        if let flutterViewController = mainFlutterWindow?.contentViewController as? FlutterViewController {
            let firebaseMessagingChannel = FlutterMethodChannel(name: "plugins.flutter.io/firebase_messaging",
                                                                binaryMessenger: flutterViewController.engine.binaryMessenger)
            
            // Ensure method call handler is set
            firebaseMessagingChannel.setMethodCallHandler { [weak self] (call: FlutterMethodCall, result: @escaping FlutterResult) in
                if call.method == "getAPNSToken" {
                    self?.getAPNSToken(result: result)
                } else {
                    result(FlutterMethodNotImplemented)
                }
            }
        }
    }

    private func registerForPushNotifications() {
        UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { granted, error in
            if granted {
                DispatchQueue.main.async {
                    NSApplication.shared.registerForRemoteNotifications()
                }
            }
        }
        UNUserNotificationCenter.current().delegate = self
    }

    private func getAPNSToken(result: @escaping FlutterResult) {
        if let deviceToken = UserDefaults.standard.string(forKey: "APNSDeviceToken") {
            result(deviceToken)
        } else {
            result(FlutterError(code: "UNAVAILABLE", message: "APNS token is not available", details: nil))
        }
    }

    override func application(_ application: NSApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        // Convert device token to String
        let tokenParts = deviceToken.map { String(format: "%02.2hhx", $0) }
        let token = tokenParts.joined()
        print("APNS Token: (token)")

        // Save token for later retrieval
        UserDefaults.standard.set(token, forKey: "APNSDeviceToken")

        // Pass token to Flutter if needed
        if let flutterViewController = mainFlutterWindow?.contentViewController as? FlutterViewController {
            let firebaseMessagingChannel = FlutterMethodChannel(name: "plugins.flutter.io/firebase_messaging",
                                                                binaryMessenger: flutterViewController.engine.binaryMessenger)
            firebaseMessagingChannel.invokeMethod("FirebaseMessaging#onTokenRefresh", arguments: token)
        }
    }

    override func application(_ application: NSApplication, didFailToRegisterForRemoteNotificationsWithError error: Error) {
        print("Failed to register for remote notifications: (error.localizedDescription)")
    }
}

Flutter Code (Dart)

import 'dart:io';
import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/services.dart';
import 'package:logger/logger.dart';

abstract class FcmServices {
  static FirebaseMessaging messaging = FirebaseMessaging.instance;
  static const MethodChannel _channel = MethodChannel('plugins.flutter.io/firebase_messaging');

  static Future<void> _handleMethodCall(MethodCall call) async {
    switch (call.method) {
      case 'FirebaseMessaging#onTokenRefresh':
        String token = call.arguments;
        print('Received APNS Token: $token');
        // Handle the APNS token here, e.g., save it, send it to a server, etc.
        break;
      default:
        print('Unknown method ${call.method}');
    }
  }

  static Future<void> initialize() async {
    _channel.setMethodCallHandler(_handleMethodCall);

    NotificationSettings settings = await messaging.requestPermission(
      alert: true,
      badge: true,
      sound: true,
    );

    if (settings.authorizationStatus == AuthorizationStatus.authorized) {
      Logger().i('User granted permission');
    } else {
      Logger().w('User declined or has not accepted permission');
      return;
    }
  }

  static String personID = 'productivity';

  static Future<String?> getDeviceToken() async {
    try {
      String? token;

      if (Platform.isMacOS) {
        token = await messaging.getAPNSToken();

        if (token == null) {
          Logger().i('APNS token is null, retrying...');
          await Future<void>.delayed(
            const Duration(seconds: 3),
          );
          token = await messaging.getAPNSToken();
        }

        if (token != null) {
          Logger().i('Successfully retrieved APNS token');
          await messaging.subscribeToTopic(personID);
        } else {
          Logger().w('Failed to retrieve APNS token after retry.');
        }
      } else {
        token = await messaging.getToken();
        if (token != null) {
          Logger().i('Successfully retrieved FCM token');
          await messaging.subscribeToTopic(personID);
        } else {
          Logger().w('Failed to retrieve FCM token.');
        }
      }

      return token;
    } catch (e, s) {
      Logger().e('Error retrieving token', error: e, stackTrace: s);
      return null;
    }
  }
}

Issue

When I try to get the APNs token using FirebaseMessaging.instance.getAPNSToken() on macOS, it always returns null.

Troubleshooting Steps Taken

• Verified that the method channel is correctly set up in Swift.
• Added logging to check if the token retrieval is being reached.
• Ensured the token is saved and retrieved from UserDefaults correctly.

Questions

1. Is there something missing in my setup?
2. Are there additional configurations required for macOS to retrieve the APNs token?
3. How can I verify that push notifications are correctly set up and that the device token is being registered?

Any help or guidance would be greatly appreciated!