Add markers to a map with Firebase - kotlin

Question

I want to make an application with Kotlin and Google Maps in which the user can add markers on the Google Map and that these markers are sent to Firebase and other users can see those same markers on the map.
This is what I have done but it is not working well for me.
package com.racrapa.displayinglocationapp
import android.content.ContentValues
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.Toast
import androidx.annotation.NonNull
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.BitmapDescriptorFactory
import com.google.android.gms.maps.model.LatLng
import com.google.android.gms.maps.model.Marker
import com.google.android.gms.maps.model.MarkerOptions
import com.google.firebase.database.*
import com.google.firebase.database.ktx.database
import com.google.firebase.ktx.Firebase
import com.google.firebase.database.ValueEventListener
import com.google.firebase.database.DataSnapshot
import com.google.firebase.database.DatabaseError
import com.google.firebase.database.DatabaseReference
private const val TAG = "MapsActivity"
class MapsActivity : AppCompatActivity(), OnMapReadyCallback {
private lateinit var mMap: GoogleMap
public lateinit var databaseRef: DatabaseReference
private lateinit var database: DatabaseReference
private var markers: MutableList<Marker> = mutableListOf()
private var postListener: ValueEventListener? = null
var mDatabase: DatabaseReference? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_maps)
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
val mapFragment = supportFragmentManager
.findFragmentById(R.id.map) as SupportMapFragment
mapFragment.getMapAsync(this)
databaseRef = Firebase.database.reference
mDatabase = FirebaseDatabase.getInstance().reference.child("userlocation")
database = Firebase.database.reference
}
This is to get the data from Firebase
public override fun onStart() {
super.onStart()
var postListener: ValueEventListener = object : ValueEventListener {
override fun onDataChange(dataSnapshot: DataSnapshot) {
if (dataSnapshot.exists()) {
val locationlogging = dataSnapshot.child("userlocation").getValue(LocationLogging::class.java)
var driverLat=locationlogging?.Latitude
var driverLong=locationlogging?.Longitude
if (driverLat != null && driverLong != null) {
val driverLoc = LatLng(driverLat, driverLong)
val markerOptions = MarkerOptions().position(driverLoc).title("Driver")
mMap.addMarker(markerOptions)
Toast.makeText(applicationContext, "Locations accessed from the database", Toast.LENGTH_LONG).show()
}
}
}
override fun onCancelled(error: DatabaseError) {}
}
databaseRef.addValueEventListener(postListener)
}
override fun onMapReady(googleMap: GoogleMap) {
mMap = googleMap
mMap.setOnMapLongClickListener { latLng ->
Log.i(TAG, "onMapLongClickListener")
setMapLongClick(latLng)
}
}
This is the function of sending coordinates to Firebase
private fun setMapLongClick(latLng: LatLng) {
if (latLng != null) {
Log.e("Latitude: ", latLng.latitude.toString() + "longitude: " + latLng.longitude)
val latlang: MutableMap<String, Double> = HashMap()
latlang["latitude"] = latLng.latitude
latlang["longitude"] = latLng.longitude
mDatabase!!.child("userlocation").push().setValue(latlang)
onStart()
}
}
}