Flutter Mapbox how to show current position of my cars

I have a flutter projects which aims to show current location of my cars in Mapbox. I use 'mapbox_gl (0.1.0)' package and show location of my cars with addSymbol function of MapboxMapController in MapboxMap widget. My MapboxMap widget is in StreamBuilder and I read locations of my cars from Firebase Realtime Database. The problem is when I change the location of my car from database the current location doesn't show up. Also, when I click hot reload button the location doesn't change as well.

Here is my code:

StreamBuilder(
      stream: FirebaseDatabase.instance
          .reference()
          .child("Vehicle")
          .onValue,
      builder: (context, snapShot) {
        if (snapShot.hasData) {
          print(snapShot.data.snapshot.value.toString());
          Map data = snapShot.data.snapshot.value;
          List item = [];
          
          data.forEach(
                  (index, data) => item.add({"key":index, ...data}));
          

          return MapboxMap(

              accessToken: token,
              
              initialCameraPosition: CameraPosition(
                zoom: 15,
                target: LatLng(38.470353, 27.076155),
              ),
              onMapCreated:
                  (MapboxMapController controller) async {
                final result = await acquireCurrentLocation();


                //this line moves camera to my current location
                await controller.moveCamera(
                  CameraUpdate.newLatLng(result),
                );

                await controller.addCircle(
                  CircleOptions(
                    circleRadius: 8.0,
                    circleColor: '#006992',
                    circleOpacity: 0.8,
                    geometry: result,
                    draggable: false,
                  ),
                );



                await controller.addSymbol(SymbolOptions(
                  geometry: LatLng(item[0]['location']['latitude'], item[0]['location']['longitude']),
                  iconSize: 0.5,
                  iconImage: getIconImage(double.parse(item[0]['battery_percent'])),
                  draggable: false,
                ));
                await controller.addSymbol(
                  SymbolOptions(
                    geometry: LatLng(item[1]['location']['latitude'], item[1]['location']['longitude']),
                    draggable: false,
                    iconSize: 0.5,

                    iconImage: getIconImage(double.parse(item[1]['battery_percent'])),

                  ),
                );
               
              });
        }

        if (snapShot.hasError) {
          return Text("Error");
        } else {
          return Center(child: CircularProgressIndicator());
        }
      });

Why do hot reload and changes in database not affect the map. The symbols that show the locations of my cars stay in the same place unless I rerun the application? What should I do?