Using Provider about mqtt.dart-client-example

[jsuofga]

We narrowed the problem down.

It appears for some reason that the var myData does not get updated inside the client.updates.listen()

class MQTTClientWrapper extends ChangeNotifier{

MqttServerClient client;
MqttCurrentConnectionState connectionState = MqttCurrentConnectionState.IDLE;
MqttSubscriptionState subscriptionState = MqttSubscriptionState.IDLE;

var myData = 'TestValue' ; //Need to pass updates to widget, using Provider

// using async tasks, so the connection won't hinder the code flow
void prepareMqttClient() async {
_setupMqttClient();
await _connectClient();
_subscribeToTopic('Dart/Mqtt_client/testtopic');
_publishMessage('HelloWorld');
}

// waiting for the connection, if an error occurs, print it and disconnect
Future _connectClient() async {
try {
print('client connecting....');
connectionState = MqttCurrentConnectionState.CONNECTING;
await client.connect('octava', 'mqtt.7078');
} on Exception catch (e) {
print('client exception - $e');
connectionState = MqttCurrentConnectionState.ERROR_WHEN_CONNECTING;
client.disconnect();
}

// when connected, print a confirmation, else print an error
if (client.connectionStatus.state == MqttConnectionState.connected) {
  connectionState = MqttCurrentConnectionState.CONNECTED;
  print('client connected');

} else {
  print(
      'ERROR client connection failed - disconnecting, status is ${client.connectionStatus}');
  connectionState = MqttCurrentConnectionState.ERROR_WHEN_CONNECTING;
  client.disconnect();
}

}

void _setupMqttClient() {
client = MqttServerClient.withPort('5f06cdd1ba6f41858989ad188f4478bb.s2.eu.hivemq.cloud', 'octavaClient', 8883);
// the next 2 lines are necessary to connect with tls, which is used by HiveMQ Cloud
client.secure = true;
client.securityContext = SecurityContext.defaultContext;
client.keepAlivePeriod = 20;
client.onDisconnected = _onDisconnected;
client.onConnected = _onConnected;
client.onSubscribed = _onSubscribed;
}

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;
  print(myData);
  // notifyListeners();
});