not working in isolate

[marcocatelli]

Hi, first of all thank you for your precious work.
I would like to run the discover inside an isolate so that it doesn't keep the main thread busy, but is not working.

This is the error:
Exception has occurred.
_AssertionError ('package:flutter/src/services/platform_channel.dart': Failed assertion: line 554 pos 7: '_binaryMessenger != null || BindingBase.debugBindingType() != null': Cannot set the method call handler before the binary messenger has been initialized. This happens when you call setMethodCallHandler() before the WidgetsFlutterBinding has been initialized. You can fix this by either calling WidgetsFlutterBinding.ensureInitialized() before this or by passing a custom BinaryMessenger instance to MethodChannel().)

and this is the code of my isolate:

void searchServerIsolate(SendPort sp) async {
sp.send(IsolateStatus.working);
ZeroConnect zc = ZeroConnect();
Set advertisers = await zc.scan(
serviceId: Const.serviceId,
time: const Duration(seconds: 3),
);
List newServerList = [];
for (Ad advertiser in advertisers) {
final sock =
await Socket.connect(advertiser.addresses.first, Const.serverPort);
sock.write('requestName');
await sock.flush();
await for (Uint8List data in sock) {
String serverName = String.fromCharCodes(data);
Bc2pcServer server = Bc2pcServer(
name: serverName,
hostName: advertiser.addresses.first,
available: true);
if (newServerList.firstWhereOrNull((test) => test.name == serverName) ==
null) {
newServerList.add(server);
}
}
}
sp.send(IsolateStatus.paused);
sp.send(newServerList);
}

WidgetsFlutterBinding.ensureInitialized() has been called in the main thread but the isolate is another thread and there is no option to call WidgetsFlutterBinding.ensureInitialized() inside the isolate because it must be called from within the UI thread.

Is there a solution to this? Do you have something for me to try in mind?

Ciao, thank you!

Marco

[Erhannis]

Sorry; I didn't see your post until now.

And also, hmm - poking around, it looks like Flutter doesn't currently support some things from isolates: flutter/flutter#130570 . Annoying, I know. Though, I don't know why it would be contingent on disabling service type validation; seems like the same code should get called.

I'd imagine that if NSD under the hood failed to register a callback, ZeroConnect would likewise not be notified of things. I'm also not sure how to fix it, until Flutter adds support for it. Sorry. :/ There's probably workarounds you could do, but they're probably pretty hacky or don't save you a lot of computation.

[Erhannis]

Btw, usually I use Futures rather than Isolates. It's usually fast enough, unless you're doing quite a bit of processing. Plus, there's a lot fewer restrictions and requirements on Futures than there are on Isolates.