flutter_background_service not receiving updates - flutter

Question

I'm using awesome_notifications and flutter_background_service in conjunction to update some app state when receiving data notifications from FirebaseMessaging. As noted in the awesome_notifications, the background message handler must be a top-level function, so I am using flutter_background_service to pass data to the main isolate and update app state.
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
await initializeBackgroundService();
FirebaseMessaging.onBackgroundMessage(_backgroundMessageHandler);
_initLocalNotifications();
runApp(MyApp());
}
I'm initializing the background service similarly to the example in flutter_background_service:
Future<void> initializeBackgroundService() async {
final service = FlutterBackgroundService();
await service.configure(
androidConfiguration: AndroidConfiguration(
onStart: onStart,
autoStart: true,
isForegroundMode: true,
),
iosConfiguration: IosConfiguration(
autoStart: true,
onForeground: onStart,
onBackground: onIosBackground,
),
);
await service.startService();
}
and invoking update in the _backgroundMessageHandler when a notification is received:
Future<void> _backgroundMessageHandler(
RemoteMessage message,
) async {
final service = FlutterBackgroundService();
...
service.invoke('update', {
'key1': 'val1',
'key2': 'val2',
});
}
And in the StatefulWidget for my app in the main isolate, I'm listening on the update call to receive the data:
void listenForNotificationData() {
final backgroundService = FlutterBackgroundService();
backgroundService.on('update').listen((event) async {
print('received data message in feed: $event');
}, onError: (e, s) {
print('error listening for updates: $e, $s');
}, onDone: () {
print('background listen closed');
});
}
It's never invoking the listen callback on the 'update' event. I can confirm it's calling the invoke('update') portion and calling on('update').listen, but never receiving the update. It also doesn't seem to be erroring out. Am I missing a step somewhere here?

Answer 1

I was encountering the same issue on flutter background service. I solved it by removing the async keyword from the callback and creating a separate async function to perform the callback operations.
void listenForNotificationData() {
final backgroundService = FlutterBackgroundService();
backgroundService.on('update').listen((event) {
print('received data message in feed: $event');
}, onError: (e, s) {
print('error listening for updates: $e, $s');
}, onDone: () {
print('background listen closed');
});
}
void action(Map? event) async {
print('received data message in feed: $event');
}
Hope it helps, forgive me if there are syntax error

Answer 2

You can try this.
main(){
....
}
Future<void> readyForShared() async {
var sharedPreferences = await SharedPreferences.getInstance();
counterValue = sharedPreferences.getString("yourVariable") ?? "0";
}
Future<void> saveData(String value) async {
var sharedPreferences = await SharedPreferences.getInstance();
sharedPreferences.setString("yourVariable", value);
}
#pragma('vm:entry-point')
void onStart(ServiceInstance service) async {
// Only available for flutter 3.0.0 and later
DartPluginRegistrant.ensureInitialized();
// For flutter prior to version 3.0.0
// We have to register the plugin manually
SharedPreferences preferences = await SharedPreferences.getInstance();
await preferences.setString("hello", "world");
/// OPTIONAL when use custom notification
final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();
if (service is AndroidServiceInstance) {
service.on('setAsForeground').listen((event) {
service.setAsForegroundService();
});
service.on('setAsBackground').listen((event) {
service.setAsBackgroundService();
});
}
service.on('stopService').listen((event) {
service.stopSelf();
});
// bring to foreground
Timer.periodic(const Duration(seconds: 1), (timer) async {
final receivePort = ReceivePort();
// here we are passing method name and sendPort instance from ReceivePort as listener
await Isolate.spawn(computationallyExpensiveTask, receivePort.sendPort);
if (service is AndroidServiceInstance) {
if (await service.isForegroundService()) {
//It will listen for isolate function to finish
// receivePort.listen((sum) {
// flutterLocalNotificationsPlugin.show(
// 888,
// 'Title',
// 'Description ${DateTime.now()}',
// const NotificationDetails(
// android: AndroidNotificationDetails(
// 'my_foreground',
// 'MY FOREGROUND SERVICE',
// icon: 'ic_bg_service_small',
// ongoing: true,
// ),
// ),
// );
// });
var sharedPreferences = await SharedPreferences.getInstance();
await sharedPreferences.reload(); // Its important
service.setForegroundNotificationInfo(
title: "My App Service",
content: "Updated at ${sharedPreferences.getString("yourVariable") ?? 'no data'}",
);
}
}
/// you can see this log in logcat
if (kDebugMode) {
// print('FLUTTER BACKGROUND SERVICE: ${deee.toString()}');
}
// test using external plugin
final deviceInfo = DeviceInfoPlugin();
String? device;
if (Platform.isAndroid) {
final androidInfo = await deviceInfo.androidInfo;
device = androidInfo.model;
}
if (Platform.isIOS) {
final iosInfo = await deviceInfo.iosInfo;
device = iosInfo.model;
}
service.invoke(
'update',
{
"current_date": '400',
"device": device,
},
);
});
}
....
....
....
class _MyAppState extends State<MyApp> {
#override
void initState() {
super.initState();
readyForShared(); // init shared preferences
});
}
...
...
...
ElevatedButton(onPressed:(){saveData('Your Updated data.');}....