flutter
On hot restart, the main thread and isolated threads will cause devtools to show a paused state
https://github.com/user-attachments/assets/87e149ac-3274-41b8-9a25-7cc3e7bd46bd
Each time, it needs to be clicked twice to restore before it can run normally. Is there any way to solve this problem
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This looks like a duplicate of https://github.com/flutter/devtools/issues/9185. @maxfrees is there something fundamentally different between these two issues? If not, it would be best to keep the communication on a single issue so that context is not lost.
Hi @maxfrees. Per Flutter issue hygiene guidelines, please refrain from adding comments that are just asking for updates. "Asking for updates is also not generally helpful, because it just leads to issues being full of comments asking for updates and that makes finding useful information in a bug harder." This issue will be updated when we have an update to share. Thanks!
Can you provide clear reproduction steps? That would help our team to resolve the problem. Thanks.
@kenzieschmoll
import 'dart:isolate';
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Isolate Demo',
theme: ThemeData(colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple)),
home: const MyHomePage(title: 'Flutter Isolate Demo'),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({super.key, required this.title});
final String title;
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class IsolateMessage {
final int value;
final SendPort responsePort;
IsolateMessage(this.value, this.responsePort);
}
class _MyHomePageState extends State<MyHomePage> {
final int _counter = 0;
String _isolateResult = "No result yet";
bool _isCalculating = false;
int _inputValue = 1000000;
ReceivePort? _receivePort;
Isolate? _isolate;
SendPort? _isolateSendPort;
void _startHeavyTask() async {
if (_isCalculating) return;
setState(() {
_isCalculating = true;
_isolateResult = "..";
});
_receivePort = ReceivePort();
_isolate = await Isolate.spawn(_isolateEntryPoint, _receivePort!.sendPort);
_receivePort!.listen((message) {
if (message is SendPort) {
_isolateSendPort = message;
_sendMessageToIsolate();
} else {
setState(() {
_isolateResult = "message: $message";
_isCalculating = false;
});
_cleanupIsolate();
}
});
}
void _sendMessageToIsolate() {
if (_isolateSendPort != null) {
final responsePort = ReceivePort();
_isolateSendPort!.send(IsolateMessage(_inputValue, responsePort.sendPort));
responsePort.listen((message) {
setState(() {
_isolateResult = "s: $message";
});
responsePort.close();
});
}
}
void _cleanupIsolate() {
_isolate?.kill(priority: Isolate.immediate);
_isolate = null;
_receivePort?.close();
_receivePort = null;
_isolateSendPort = null;
}
static void _isolateEntryPoint(SendPort mainSendPort) {
final receivePort = ReceivePort();
mainSendPort.send(receivePort.sendPort);
receivePort.listen((message) {
if (message is IsolateMessage) {
int limit = message.value;
message.responsePort.send("limit: $limit");
int sum = 0;
for (int i = 0; i < limit; i++) {
sum += i;
}
mainSendPort.send(sum);
}
});
}
@override
void dispose() {
_cleanupIsolate();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(backgroundColor: Theme.of(context).colorScheme.inversePrimary, title: Text(widget.title)),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text('demo:'),
Text('$_counter', style: Theme.of(context).textTheme.headlineMedium),
const SizedBox(height: 30),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 50),
child: TextField(
keyboardType: TextInputType.number,
onChanged: (value) {
if (value.isNotEmpty) {
_inputValue = int.tryParse(value) ?? 1000000;
}
},
),
),
const SizedBox(height: 20),
ElevatedButton(
onPressed: _isCalculating ? null : _startHeavyTask,
child: Text(_isCalculating ? 'send...' : 'send'),
),
const SizedBox(height: 20),
Text(_isolateResult),
],
),
),
);
}
}
https://github.com/user-attachments/assets/6425fa51-31d9-4c97-846e-7b8be49e350a
Thank you for the code snippet. It is not immediately clear from your video what the reproduction steps are. Can you provide textual instructions like:
- Run app on from VS code on Desktop.
- Trigger a hot restart. Expected behavior: ... Actual behavior: ....
Clear instructions like this make it easier to reproduce your use case.
Additionally, I don't actually see where DevTools is used in your video. Are you actually opening Flutter DevTools at any point during your workflow?
If the code contains an isolation thread, Each time a hot restart is performed and the "Send Isolation Thread Message" is clicked, there is a probability that the thread will be in a paused state, blocking the code execution. It is necessary to manually click "Start" for it to execute.
