Issue
i’m developing a VoIP app and having problem with background handler. What i want is: sending push with type "call" then the app will show Call UI, later if receive push type "hangup" , the app will close that call UI.
In background handler i’m using a singleton global class to inform hang up event with a StreamController and CallScreen widget will listen to that stream to close itself.
Then i found out that flutterfire will start another isolate for background handler (turn screen off) , so it will create another singleton class -> i can’t close my CallScreen UI with this new singleton class.
Is it possible to do something like this with flutterfire’s background isolate ?
Example pseudo code:
class SingletonGlobal {
/// singleton class
final hangUpStreamController = StreamController<HangUpEvent>.broadcast();
void addHangupEvent(HangUpEvent event) {
hangUpStreamController.add(event);
}
}
class CallScreen extends StatefulWidget {
//// ...
@override
void initState() {
SingletonGlobal().hangUpStreamController.stream.listen((event) => closeCallUI(event));
}
}
Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
await Firebase.initializeApp();
await appInit();
if (message.data.type = 'hangup') {
SingletonGlobal().addHangupEvent(hangUpEvent);
}
Update
I tried Nitrodon’s solution. but as I mentioned, _firebaseMessagingBackgroundHandler will create another instance of my SingleGlobal class. i don’t know why.
"SingletonGlobal#internal" printed again after receive firebase background handler. that’s mean it recreated SingletonGlobal.
class SingletonGlobal {
/// singleton class
static SingletonGlobal? _instance;
final _receivePort = ReceivePort();
factory SingletonGlobal() => _instance ?? SingletonGlobal._internal();
SingletonGlobal._internal() {
print('SingletonGlobal#internal');
IsolateNameServer.registerPortWithName(_receivePort.sendPort, 'global_singleton');
_receivePort.listen((message) => hangUpStreamController.add);
_instance = this;
}
}
Solution
There are ways to communicate between isolates. In this case, since you only need to listen to events on the main isolate, you can register a port to receive hangup events from the background isolate:
class SingletonGlobal {
// Whatever private constructor you're using for this singleton
SingletonGlobal._() {
IsolateNameServer.registerPortWithName(_receivePort.sendPort, 'some port name');
_receivePort.listen(hangUpStreamController.add);
}
final hangUpStreamController = StreamController<HangUpEvent>.broadcast();
final _receivePort = ReceivePort();
void addHangupEvent(HangUpEvent event) {
hangUpStreamController.add(event);
}
}
void _firebaseMessagingBackgroundHandler(RemoteMessage message) {
// Do not try to access SingletonGlobal here.
if (message.data.type = 'hangup') {
// Since the background isolate is still in the same process, you
// can send objects (which are copied) instead of just basic messages.
IsolateNameServer.lookupPortByName('some port name')?.send(hangUpEvent);
}
}
Answered By – Nitrodon
Answer Checked By – Robin (FlutterFixes Admin)