hivemq-cloud / mqtt.dart-client-example Goto Github PK

dart pub get
Resolving dependencies...
The lower bound of "sdk: '>=2.1.0 <3.0.0'" must be 2.12.0'
or higher to enable null safety.

The current Dart SDK (3.1.4) only supports null safety.

For details, see https://dart.dev/null-safety

We are able to Publish a new message ( every 5sec) and able to Subscribe to the message.
We do see the new message update in the terminal from the print(message) from the client.updates.listen() block.

Problem:
We then modified the MQTTClientWrapper with 'extends changeNotifier'

so with client.updates.listen() occurs, we pass the data to a widget using Provider

void _subscribeToTopic(String topicName) {
print('Subscribing to the $topicName topic');
client.subscribe(topicName, MqttQos.atMostOnce);

// print the message when it is received
client.updates.listen((List<MqttReceivedMessage<MqttMessage>> c) {
  final MqttPublishMessage recMess = c[0].payload;
  var message = MqttPublishPayload.bytesToStringAsString(recMess.payload.message);

  print('YOU GOT A NEW MESSAGE:');
  print(message);  // Displays message correctly

  myData = message;
  notifyListeners();

});

In the top level widget, we pass the Provider down to the Text() widget , but the update never seem to occur.

Text(Provider.of(context,listen: true).myData , // This is not receiving the changeNotifier 'myData'
style: TextStyle(fontSize: 10,color: Colors.white),),

}

Any insight on why the notifyListeners inside the client.updates.listen() is not functions?