iazel
commented
2 weeks ago After further analysis on Android, in case the main Activity is destroyed (i.e. AppLifecycleState.detached), even though the Isolate still runs in background, once we open back the app, port will be limited on sending data as if they didn't share the same codebase.
Notice that even if we get paused, the app will work without problems. It is only the detached state that causes problems.
This can be easily tested on Android by enabling Don't keep activities in Developer options settings.
Code sample:
import 'dart:async';
import 'dart:isolate';
import 'dart:ui';
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
final class A {}
final class MyApp extends StatefulWidget {
const MyApp({super.key});
@override
State<StatefulWidget> createState() {
return _MyAppState();
}
}
final class _MyAppState extends State<MyApp> {
@override
void initState() {
super.initState();
final port = IsolateNameServer.lookupPortByName('name');
if (port == null) {
Isolate.spawn((_) async {
final port = ReceivePort();
port.listen((message) {
print('got $message');
});
IsolateNameServer.registerPortWithName(port.sendPort, 'name');
var i = 0;
while (true) {
++i;
await Future<void>.delayed(const Duration(seconds: 5));
print('looped $i times');
}
}, null);
} else {
port.send(A());
}
}
@override
Widget build(BuildContext context) {
return const MaterialApp(
home: Scaffold(
body: Text('Hello World'),
),
);
}
}By changing send to something like:
port.send('restarted');It will work as expected.
huycozy
a-siva
aam
Steps to reproduce
IsolateNameServer.registerPortWithNamelistenon the port, orclosethe port, orIsolate.kill()the given isolateIsolateNameServer.lookupPortByNamesendPlease be aware that it is important to send a custom class, otherwise the issue does not exist.
Another interesting aspect is that if we get
portbefore it is closed, and keep using it, then no issue arise.Expected results
Ports normally exhibit the following behavior:
listenis calledActual results
When using data types supported across different code-bases (e.g: int, string, etc...), no issues arise.
When using data types supported only on same code-bases (e.g. custom classes), then
ArgumentErroris thrown onport.sendif the receiving end is somehow closed or not ready.Code sample
Code sample
```dart import 'dart:isolate'; import 'dart:ui'; import 'package:flutter_test/flutter_test.dart'; final class A { } void main() { test('isolate', () async { TestWidgetsFlutterBinding.ensureInitialized(); await Isolate.spawn( (_) { final port = ReceivePort(); port.listen((_) { Isolate.exit(); }); IsolateNameServer.registerPortWithName(port.sendPort, 'test'); }, null, ); while (IsolateNameServer.lookupPortByName('test') == null) { await FutureScreenshots or Video
No response
Logs
Logs
```console dart:isolate _SendPort.send test/isolate_test.dart 28:51 main.Flutter Doctor output
Doctor output
```console Doctor summary (to see all details, run flutter doctor -v): [✓] Flutter (Channel stable, 3.19.6, on Ubuntu 23.10 6.5.0-28-generic, locale en_US.UTF-8) [✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0) [✓] Chrome - develop for the web [✓] Linux toolchain - develop for Linux desktop [✓] Android Studio (version 2023.2) [✓] IntelliJ IDEA Community Edition (version 2023.3) [✓] Connected device (2 available) [✓] Network resources • No issues found! ```