Google MapView with Fragment

MapFragment.java

class MapsFragment : Fragment(), OnMapReadyCallback {

    private lateinit var mMap: GoogleMap

    private var mapView: MapView? = null

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val v = inflater.inflate(R.layout.fragment_maps, container, false)

        mapView = v.mapView

        mapView?.getMapAsync(this)

        return v
    }

    /**
     * Manipulates the map once available.
     * This callback is triggered when the map is ready to be used.
     * This is where we can add markers or lines, add listeners or move the camera. In this case,
     * we just add a marker near Sydney, Australia.
     * If Google Play services is not installed on the device, the user will be prompted to install
     * it inside the SupportMapFragment. This method will only be triggered once the user has
     * installed Google Play services and returned to the app.
     */
    override fun onMapReady(googleMap: GoogleMap) {
        mMap = googleMap

        // Add a marker in Sydney and move the camera
        val sydney = LatLng(-34.0, 151.0)
        mMap.addMarker(MarkerOptions().position(sydney).title("Marker in Sydney"))
        mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney))
    }


    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        mapView?.onSaveInstanceState(outState)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        mapView?.onCreate(savedInstanceState)
    }

    override fun onResume() {
        mapView?.onResume()
        super.onResume()
    }

    override fun onStart() {
        super.onStart()
        mapView?.onStart()
    }

    override fun onPause() {
        super.onPause()
        mapView?.onPause()
    }

    override fun onStop() {
        super.onStop()
        mapView?.onStop()
    }


    override fun onDestroyView() {
        super.onDestroyView()
        mapView?.onDestroy()
    }

    override fun onLowMemory() {
        super.onLowMemory()
        mapView?.onLowMemory()
    }
}


----- fragments_map.xml ----------------------------------------------------------------------------------

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_height="match_parent"
    android:layout_width="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <com.google.android.gms.maps.MapView
        android:id="@+id/mapView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>