Flutter: run code like a timer when app is running in background - flutter

Question

I have a simple timer which works fine when the app is running in foreground. I can listen to the stream and update the UI. However when the app is in the background it will not continue counting. How can I continue counting when the app is running in the background?
This is my code for the timer:
class SetTimer {
int _seconds = 0;
final _streamController = StreamController<int>.broadcast();
Timer? _timer;
// Getters
Stream<int> get stream => _streamController.stream;
// Setters
void start() {
_timer = Timer.periodic(const Duration(seconds: 1), (_) {
_seconds++;
_updateSeconds();
});
}
void _updateSeconds() {
// stop counting after one hour
if (_seconds < 3600) {
_streamController.sink.add(_seconds);
}
}
}

Answer 1

Try the below code -
I tested it & found it will count the number in the background & there is no problem.
I added a screen record video here, it will help you to understand.
import 'dart:async';
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return const MaterialApp(
title: 'Flutter Demo',
home: MyTest(),
);
}
}
class MyTest extends StatefulWidget {
const MyTest({Key? key}) : super(key: key);
#override
State<MyTest> createState() => _MyTestState();
}
class _MyTestState extends State<MyTest> {
final SetTimer _setTimer = SetTimer();
#override
void initState() {
_setTimer.start();
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: StreamBuilder<int>(
stream: _setTimer.stream,
builder: (
BuildContext context,
AsyncSnapshot<int> snapshot,
) {
if (snapshot.connectionState == ConnectionState.waiting) {
return CircularProgressIndicator();
} else if (snapshot.connectionState == ConnectionState.active
|| snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
return const Text('Error');
} else if (snapshot.hasData) {
return Center(
child: Text(
snapshot.data.toString(),
style: const TextStyle(color: Colors.red, fontSize: 40)
),
);
} else {
return const Text('Empty data');
}
} else {
return Text('State: ${snapshot.connectionState}');
}
},
),
);
}
}
class SetTimer {
int _seconds = 0;
final _streamController = StreamController<int>.broadcast();
Timer? _timer;
// Getters
Stream<int> get stream => _streamController.stream;
// Setters
void start() {
_timer = Timer.periodic(const Duration(seconds: 1), (_) {
_seconds++;
_updateSeconds();
});
}
void _updateSeconds() {
// stop counting after one hour
if (_seconds < 3600) {
_streamController.sink.add(_seconds);
}
}
}

Answer 2

As far as I know, there is no way to run the app in the background, like you want to. I had a similar problem with an app, I developed and didn't found the perfect solution.
As a workaround, I'm using the wakelock package to prevent the mobile device / app from going into standby. Maybe this could also be a solution for you.