Flutter Android Foreground Example

AndroidManifest.xml

<manifest ...>
    // add following line
    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
    <application
        ...
        // add following line
        <service android:name=".ExampleService" />
    </application>
</manifest>

ExampleService.kt

// change 'flutter_foreground_example' to your app name
package com.example.flutter_foreground_example

import androidx.annotation.RequiresApi
import android.content.Context
import android.graphics.Color
import android.app.Notification
import android.app.NotificationManager
import android.app.NotificationChannel
import android.app.Service
import android.content.Intent
import android.os.Build
import android.os.IBinder
import androidx.core.app.NotificationCompat
import java.util.Timer
import java.util.TimerTask

class ExampleService : Service() {
    val notificationId = 1
    var serviceRunning = false
    lateinit var builder: NotificationCompat.Builder
    lateinit var channel: NotificationChannel
    lateinit var manager: NotificationManager

    override fun onCreate() {
        super.onCreate()
        startForeground()
        serviceRunning = true
        Timer().schedule(object : TimerTask() {
            override fun run() {
                if (serviceRunning == true) {
                    updateNotification("I got updated!")
                }
            }
        }, 5000)
    }

    override fun onDestroy() {
        super.onDestroy()
        serviceRunning = false
    }

    @RequiresApi(Build.VERSION_CODES.O)
    private fun createNotificationChannel(channelId: String, channelName: String): String {
        channel = NotificationChannel(channelId,
                channelName, NotificationManager.IMPORTANCE_NONE)
        channel.lightColor = Color.BLUE
        channel.lockscreenVisibility = Notification.VISIBILITY_PRIVATE
        manager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
        manager.createNotificationChannel(channel)
        return channelId
    }

    private fun startForeground() {
        val channelId =
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                createNotificationChannel("example_service", "Example Service")
            } else {
                // If earlier version channel ID is not used
                // https://developer.android.com/reference/android/support/v4/app/NotificationCompat.Builder.html#NotificationCompat.Builder(android.content.Context)
                ""
            }
        builder = NotificationCompat.Builder(this, channelId)
        builder
            .setOngoing(true)
            .setOnlyAlertOnce(true)
            .setSmallIcon(R.mipmap.ic_launcher)
            .setContentTitle("Example Service")
            .setContentText("Example Serivce is running")
            .setCategory(Notification.CATEGORY_SERVICE)
        startForeground(1, builder.build())
    }

    private fun updateNotification(text: String) {
        builder
            .setContentText(text)
        manager.notify(notificationId, builder.build());
    }

    override fun onBind(intent: Intent): IBinder? {
        return null
    }
}

main.dart

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'dart:async';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Foreground Example',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Foreground Example Home Page'),
    );
  }
}

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

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

class _MyHomePageState extends State<MyHomePage> {
  static const platform = const MethodChannel('example_service');
  String _serverState = 'Did not make the call yet';

  Future<void> _startService() async {
    try {
      final result = await platform.invokeMethod('startExampleService');
      setState(() {
        _serverState = result;
      });
    } on PlatformException catch (e) {
      print("Failed to invoke method: '${e.message}'.");
    }
  }

  Future<void> _stopService() async {
    try {
      final result = await platform.invokeMethod('stopExampleService');
      setState(() {
        _serverState = result;
      });
    } on PlatformException catch (e) {
      print("Failed to invoke method: '${e.message}'.");
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          children: [
            Text(_serverState),
            ElevatedButton(
              child: Text('Start Service'),
              onPressed: _startService,
            ),
            ElevatedButton(
              child: Text('Stop Service'),
              onPressed: _stopService,
            ),
          ],
        ),
      ),
    );
  }
}

MainActivity.kt

// change 'flutter_foreground_example' to your app name
package com.example.flutter_foreground_example

import android.content.Intent
import androidx.annotation.NonNull
import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodChannel
import io.flutter.plugins.GeneratedPluginRegistrant

class MainActivity : FlutterActivity() {
    private val CHANNEL = "example_service"

    override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler {
            // Note: this method is invoked on the main thread.
            call, result ->
            when (call.method) {
                "startExampleService" -> {
                    startService(Intent(this, ExampleService::class.java))
                    result.success("Started!")
                }
                "stopExampleService" -> {
                    stopService(Intent(this, ExampleService::class.java))
                    result.success("Stopped!")
                }
                else -> {
                    result.notImplemented()
                }
            }
        }
    }
}