In Flutter How to use Providers with AMQP? - flutter

Question

in Flutter -which I just recently begin to use-, I am trying to use an AMQP stream using dart_amqp: ^0.1.4 and use providers provider: ^3.1.0+1 to make the data available throughout the app.
Only after logging in I start the AMQP service.
The AMQP part works without any issues, I get the data but I never manage to use it with Providers.
main.dart
class BigBrother extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MultiProvider(
providers: [
ChangeNotifierProvider<EventsModel>(create: (_) => EventsModel()),
ChangeNotifierProxyProvider<EventsModel, DeviceState>(
create: (_) => new DeviceState(),
update: (context, eModel, deviceState) {
deviceState.updateFromEvent(eModel.value);
},
),
],
My models in models.dart
(As seen in below code, I also tried to used StreamProvider and commented it out)
// Global data model
class DeviceState with ChangeNotifier {
Map<String, Map<String, dynamic>> state = {};
DeviceState() {
this.state['xxx'] = {};
this.state['yyy'] = {};
}
updateFromEvent(EventsItemModel event) {
if (event != null && event.type != null) {
switch (event.type) {
case 'heartbeat':
this.state[event.device][event.type] = event.createdAt;
break;
case 'metrics':
this.state[event.device][event.type] = {}
..addAll(this.state[event.device][event.type])
..addAll(event.message);
break;
}
notifyListeners();
}
}
}
class EventsModel with ChangeNotifier {
EventsItemModel value;
bool isSubscribed = false;
AMQPModel _amqp = new AMQPModel();
// final _controller = StreamController<EventsItemModel>();
EventsModel();
// Stream<EventsItemModel> get stream => _controller.stream;
_set(String jsonString) {
value = new EventsItemModel.fromJson(jsonString);
// _controller.sink.add(value); // send data to stream
// Provider.of<DeviceState>(context, listen: false).updateFromEvent(value);
notifyListeners();
}
subscribe() {
if (!this.isSubscribed) {
this.isSubscribed = true;
this._amqp.subscribeEvents(_set); // start AMQP service after login
}
}
}
So on the login.dart view, on button pressed and validating the login, I start the AMQP stream:
onPressed: () {
if (_formKey.currentState.validate()) {
print("Login button onPressed");
Provider.of<EventsModel>(context, listen: false)
.subscribe();
Navigator.pushReplacementNamed(context, Routes.live);
}
And lastly the view after successful login:
class _LivePageState extends State<LivePage> {
#override
Widget build(BuildContext context) {
DeviceState deviceState = Provider.of<DeviceState>(context);
print('#### Device state updated');
print(deviceState.state['xxx']);
In the above code, deviceState is always null.
So after trying many combination of various Providers, I am still unable to make this work.
Would be glad to have someone's insight on this.
Best regards!