Retrieve location from Firebase and map it on Google Map using Android studio

Question

I am working on my tracker system which I will get the live location from GPS Module (hardware) and the data will map it on the google map in android studio. I want to retrieve the longitude and latitude and map it on the google map. Below is my code.

    package com.example.ambulancetracker;

    import androidx.annotation.NonNull;
    import androidx.fragment.app.FragmentActivity;
    import android.os.Bundle;
    import com.google.android.gms.maps.CameraUpdateFactory;
    import com.google.android.gms.maps.GoogleMap;
    import com.google.android.gms.maps.OnMapReadyCallback;
    import com.google.android.gms.maps.SupportMapFragment;
    import com.google.android.gms.maps.model.LatLng;
    import com.google.android.gms.maps.model.MarkerOptions;
    import com.example.ambulancetracker.databinding.ActivityMapsBinding;
    import com.google.firebase.database.DataSnapshot;
    import com.google.firebase.database.DatabaseError;
    import com.google.firebase.database.DatabaseReference;
    import com.google.firebase.database.FirebaseDatabase;
    import com.google.firebase.database.ValueEventListener;
    public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {
    private GoogleMap mMap;
    private ActivityMapsBinding binding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = ActivityMapsBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());
        //FirebaseDatabase.getInstance().getReference().setValue("This is a tracker app");
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }
   
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Ambulance");
        ValueEventListener listener = databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                Double latitude = snapshot.child("latitude").getValue(Double.class);
                Double longitude = snapshot.child("longitude").getValue(Double.class);
                LatLng location = new LatLng(latitude,longitude);
                mMap.addMarker(new MarkerOptions().position(location).title("Ambulance"));
                mMap.moveCamera(CameraUpdateFactory.newLatLng(location));
                mMap.setMinZoomPreference(16);
                mMap.getUiSettings().setZoomControlsEnabled(true);
                mMap.getUiSettings().setAllGesturesEnabled(true);
            }
            @Override
            public void onCancelled(@NonNull DatabaseError error) {
            }
        });
    }
}