This plugin lets you send messages to the Dart side from background processes which runs on platform side. For example, send messages from Android BroadcastReceiver, Worker or Services or IOS background fetch or any other native code which runs in background back to Dart side while app closed.

If your Flutter app contains platform logic such as Android Service ActivityRecognition (Walking, Running, Vehicle etc'), battery status, WorkerManager or IOS BackgroundFetch, Silent Push or any processes that runs when app closed and doesn't use third party plugins, you can use this plugin to send messages from these processes back to dart code in background.

Define a background callback with single parameter of type Map<String, dynamic> in your app , (must be a top level function) Insure to mark it with @pragma('vm:entry-point')

@pragma('vm:entry-point')
Future<void> appBackgroundCallback(Map<String, dynamic> params) async {
  print("[appBackgroundCallback]: received background event: $params");

}

Register your background callback on main.dart

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await FlutterBackground.instance.registerBackgroundCallback(appBackgroundCallback);
  runApp(const MyApp());
}

In your native process send events to dart in format of Map<String, Any> in Kotlin or [String: Any?] on Swift

class BootCompleteReceiver : BroadcastReceiver(){
    override fun onReceive(c: Context, intent: Intent) {
        FlutterBackgroundPlugin.emitBackgroundEvent(mapOf("action" to "BootComplete"))
    }
}

 BGTaskScheduler.shared.register(forTaskWithIdentifier: "com.example.background_fetch_identifier", using: nil) { task in
            self.handleAppRefresh(task: task as! BGAppRefreshTask)
        }

 let request = BGAppRefreshTaskRequest(identifier: "com.example.background_fetch_identifier")
 BGTaskScheduler.shared.submit(request)

 private func handleAppRefresh(task: BGAppRefreshTask) {
        var event : [String: Any?] = [:]
        event["BackgroundFetchComplete"] = task.identifier

        //Send event to Dart side
        FlutterBackgroundPlugin.emitBackgroundEvent(event: event)
    }