How to see changes in flutter app when changing values in Firebase Realtime Database?

Question

I am trying to make these rolling switches to change its value whenever I do any change in Firebase realtime database.

To be more specific, whenever I change the value of Relay1/Data to 0, I want that switch to become inactive.

I've tried and looked everywhere, but I couldn't find any solution.

  bool relay1pressed;
  final databaseReferenceTest = FirebaseDatabase.instance.reference();



@override
  void initState() {
    super.initState();

    databaseReferenceTest
        .child('MedicalCenter')
        .once()
        .then((DataSnapshot snapshot) {
      String value = snapshot.value['Relay1']['Data'];
      print('Value is $value');
      if (value == '1') {
        relay1pressed = true;
      } else
        relay1pressed = false;

      setState(() {
        isLoading = true;
      });
    });
  }

  
//Widget build

            StreamBuilder(
              stream: databaseReferenceTest
                  .child('MedicalCenter')
                  .child('Relay1')
                  .onValue,
              builder: (BuildContext context, AsyncSnapshot<Event> snapshot) {
                databaseReferenceTest
                    .child('MedicalCenter')
                    .once()
                    .then((DataSnapshot snapshot) {
                  String value = snapshot.value['Relay1']['Data'];
                  print('Value is $value');
                  if (value == '1') {
                    relay1pressed = true;
                    print('relay1 bool $relay2pressed');
                  } else {
                    relay1pressed = false;
                    print('relay1 bool $relay2pressed');
                  }
                });

                return LiteRollingSwitch(
                  value: relay1pressed,
                  textOn: 'active',
                  textOff: 'inactive',
                  colorOn: Colors.deepOrange,
                  colorOff: Colors.blueGrey,
                  iconOn: Icons.lightbulb_outline,
                  iconOff: Icons.power_settings_new,
                  onChanged: (bool state) {
                    state
                        ? databaseReferenceTest
                            .child('MedicalCenter')
                            .update({'Relay1/Data': '1'})
                        : databaseReferenceTest
                            .child('MedicalCenter')
                            .update({'Relay1/Data': '0'});
           

Answer 1

You're currently using once() to get the value from the database, which means it only reads the current value. If you want to keep monitoring the value, you'll want to use onValue instead.

databaseReferenceTest
    .child('MedicalCenter')
    .onValue.listen((event) {
      var snapshot = event.snapshot

      String value = snapshot.value['Relay1']['Data'];
      print('Value is $value');

      ...

    });