Display marker on Google Maps (Kotlin)

MapsActivity.kt

import android.Manifest
import android.content.Context
import android.location.Location
import android.os.Build
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.support.v4.app.ActivityCompat
import android.widget.Toast

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.Marker
import com.google.android.gms.maps.model.MarkerOptions
import com.google.android.gms.maps.model.BitmapDescriptorFactory


class MapsActivity : AppCompatActivity(), OnMapReadyCallback {

    private lateinit var mMap: GoogleMap
    private lateinit var currentMarker: Marker
    private lateinit var currentPosition: LatLng

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_maps)
        val mapFragment = supportFragmentManager
            .findFragmentById(R.id.map) as SupportMapFragment
        mapFragment.getMapAsync(this)
    }

    override fun onMapReady(googleMap: GoogleMap) {
        mMap = googleMap
	    
        val sydney = LatLng(-34.0, 151.0)
        mMap.addMarker(MarkerOptions().position(sydney).title("Marker in Sydney"))
        mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney))    

        mMap!!.setOnMarkerClickListener(object : GoogleMap.OnMarkerClickListener {
            override fun onMarkerClick(marker: Marker): Boolean {
                currentMarker = marker
                currentPosition = currentMarker.position
                Toast.makeText(applicationContext, "Lat: "+currentPosition.latitude+", lon: "+currentPosition.longitude, Toast.LENGTH_SHORT).show()
                return false
            }
        })

        mMap!!.setOnMapClickListener(object : GoogleMap.OnMapClickListener {
            override fun onMapClick(latLng: LatLng) {
                currentMarker.remove()
                currentMarker = mMap.addMarker(
                    MarkerOptions()
                        .position(latLng)
                        .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED))
                    )
            }
        })
    }
}