Run a method or function in dart when a callback from native android methodchannel

I need to run a dart function in the background when the methodchannel sends a callback...

here at below dart code...i want to run SendData() function when I receive any callback or return from methodchannel...

IMPORTANT *** => I wants it to work in background...even after the app is terminated...No need of UI change and all...just call the sendData() function in the background

MainActivity.Java

package com.ashbu.flutterappbackground;

import androidx.annotation.NonNull;
import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.plugin.common.EventChannel;
import io.flutter.plugin.common.MethodChannel;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.telephony.PhoneStateListener;
import android.telephony.TelephonyManager;
import android.widget.Toast;
import android.content.IntentFilter;
import io.flutter.plugin.common.EventChannel.EventSink;
import io.flutter.plugin.common.EventChannel.StreamHandler;
import android.app.Service;




public class MainActivity extends FlutterActivity {
    private static final String CHANNEL = "samples.flutter.dev/battery";
    private static final String IncomingCall_CHANNEL = "samples.flutter.dev/IncomingCall";

    AlarmManager alarmManager;
    PendingIntent pendingIntent;

    @Override
    public void configureFlutterEngine(@NonNull FlutterEngine flutterEngine) {
        super.configureFlutterEngine(flutterEngine);
        alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        Intent alarmIntent = new Intent(this, MyService.class);
        pendingIntent = PendingIntent.getBroadcast(this, 0, alarmIntent, 0);

        new EventChannel(flutterEngine.getDartExecutor(), IncomingCall_CHANNEL).setStreamHandler(
                new StreamHandler() {
                    private BroadcastReceiver IncomingCallStateChangeReceiver;
                    @Override
                    public void onListen(Object arguments, EventSink events) {
                        IncomingCallStateChangeReceiver = createIncomingCallStateChangeReceiver(events);
                        registerReceiver(
                                IncomingCallStateChangeReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
                    }

                    @Override
                    public void onCancel(Object arguments) {
                        unregisterReceiver(IncomingCallStateChangeReceiver);
                        IncomingCallStateChangeReceiver = null;
                    }

                }
        );
        new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
                .setMethodCallHandler(
                        (call, result) -> {
                            // Note: this method is invoked on the main thread.
                            if (call.method.equals("getBatteryLevel")) {
                                startAlarm();
                                MyBroadcastReceiver dataGEt = new MyBroadcastReceiver();
                                result.success(dataGEt.getData());
                            } else {
                                cancelAlarm();
                            }
                        }
                );
    }
        private BroadcastReceiver createIncomingCallStateChangeReceiver(final EventSink events){
            return new BroadcastReceiver() {
                @Override
                public void onReceive(final Context context, Intent intent) {
                    TelephonyManager telephony = (TelephonyManager) context.getSystemService(Service.TELEPHONY_SERVICE);
                    telephony.listen(new PhoneStateListener() {
                        @Override
                        public void onCallStateChanged(int state, String incomingNumber) {
                            super.onCallStateChanged(state, incomingNumber);
                            System.out.println("incomingNumber : " + incomingNumber);
                            Toast.makeText(context, "TeleDuce Customer " + incomingNumber,
                                    Toast.LENGTH_LONG).show();
                            if (incomingNumber != null) {
                                events.success(incomingNumber);
                            } else {
                                events.success("Abaha");
                            }
                        }
                    }, PhoneStateListener.LISTEN_CALL_STATE);
                }
            };
    }


    private void startAlarm() {

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            alarmManager.setAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, 0, pendingIntent);
        } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            alarmManager.setExact(AlarmManager.RTC_WAKEUP, 0, pendingIntent);
        } else {
            alarmManager.set(AlarmManager.RTC_WAKEUP, 0, pendingIntent);
        }
    }

    private void cancelAlarm() {
        alarmManager.cancel(pendingIntent);
        Toast.makeText(getApplicationContext(), "Alarm Cancelled", Toast.LENGTH_LONG).show();
    }


}

Main.Dart

import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:http/http.dart' as http;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  static const platform = const MethodChannel('samples.flutter.dev/battery');
  static const EventChannel eventChannel =
      EventChannel('samples.flutter.dev/IncomingCall');
  // Get battery level.
  String _batteryLevel = 'Unknown battery level.';
  String _IncomingCallStatus = 'Battery status: unknown.';

  Future<void> _getBatteryLevel() async {
    String batteryLevel;
    try {
      final String result = await platform.invokeMethod('getBatteryLevel');
      batteryLevel = 'Battery level at $result % .';
    } on PlatformException catch (e) {
      batteryLevel = "Failed to get battery level: '${e.message}'.";
    }

    setState(() {
      _batteryLevel = batteryLevel;
    });
  }

  Future<void> SendData() async {                <--------Need to call this function in background
    var param = {
      'userId': 272.toString(),
      'api_key': '******************',
      'env': 'production',
      'common_search': '',
      'filter_type': 'My',
      'filter_type_data': '',
      'leadsourcerequest': true,
    };
    // Get the previous cached count and increment it.
    var res = await http.post(
        'https://***********.amazonaws.com/default/Leadapi',
        body: json.encode(param));
    Map responsejson = json.decode(res.body);
    print(res);
    print(responsejson['response_data'][0]);
    // This will be null if we're running in the background.
  }

  @override
  void initState() {
    // TODO: implement initState
    eventChannel.receiveBroadcastStream().listen(_onEvent, onError: _onError);
    super.initState();
  }

  void _onEvent(Object event) {
    setState(() {
      _IncomingCallStatus = "Battery status: $event";
      SendData();                                     <-------- This need to be working on background 
      print('++++++++++++');
    });
  }

  void _onError(Object error) {
    setState(() {
      _IncomingCallStatus = 'Battery status: unknown.';
    });
  }

Actually the words like battery status, batteryCahnenl and all is because I just copied this code from flutter platform channel example...pls just ignore