Get location from google map on kotlin

get_google_map.kt

// 1. 
class LocationActivity : AppCompatActivity(), OnMapReadyCallback {

    // 2.
    private var mLocationRequest: LocationRequest? = null
    private val UPDATE_INTERVAL = (10 * 1000).toLong()  /* 10 secs */
    private val FASTEST_INTERVAL: Long = 2000 /* 2 sec */

    private var latitude = 0.0
    private var longitude = 0.0

    private lateinit var mGoogleMap: GoogleMap

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_location)

        val mapFragment = supportFragmentManager.findFragmentById(R.id.location) as SupportMapFragment
        mapFragment.getMapAsync(this)
    }

    override fun onStart() {
        super.onStart()
        startLocationUpdates()
    }
    
    override fun onMapReady(googleMap: GoogleMap) {

        mGoogleMap = googleMap;

        if (mGoogleMap != null) {
            mGoogleMap!!.addMarker(MarkerOptions().position(LatLng(latitude, longitude)).title("Current Location"))
        }

    }

    // 3.
    protected fun startLocationUpdates() {
        // initialize location request object
        mLocationRequest = LocationRequest.create()
        mLocationRequest!!.run {
            setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
            setInterval(UPDATE_INTERVAL)
            setFastestInterval(FASTEST_INTERVAL)
        }

        // initialize location setting request builder object
        val builder = LocationSettingsRequest.Builder()
        builder.addLocationRequest(mLocationRequest!!)
        val locationSettingsRequest = builder.build()

        // initialize location service object
        val settingsClient = LocationServices.getSettingsClient(this)
        settingsClient!!.checkLocationSettings(locationSettingsRequest)

        // call register location listener
        registerLocationListner()
    }

    private fun registerLocationListner() {
        // initialize location callback object
        val locationCallback = object : LocationCallback() {
            override fun onLocationResult(locationResult: LocationResult?) {
                onLocationChanged(locationResult!!.getLastLocation())
            }
        }
        // 4. add permission if android version is greater then 23
        if(Build.VERSION.SDK_INT >= 23 && checkPermission()) {
            LocationServices.getFusedLocationProviderClient(this).requestLocationUpdates(mLocationRequest, locationCallback, Looper.myLooper())
        }
    }

    //  
    private fun onLocationChanged(location: Location) {
        // create message for toast with updated latitude and longitudefa
        var msg = "Updated Location: " + location.latitude  + " , " +location.longitude

        // show toast message with updated location
        //Toast.makeText(this,msg, Toast.LENGTH_LONG).show()
        val location = LatLng(location.latitude, location.longitude)
        mGoogleMap!!.clear()
        mGoogleMap!!.addMarker(MarkerOptions().position(location).title("Current Location"))
        mGoogleMap.moveCamera(CameraUpdateFactory.newLatLng(location))
    }

    private fun checkPermission() : Boolean {
        if (ContextCompat.checkSelfPermission(this , android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            return true;
        } else {
            requestPermissions()
            return false
        }
    }

    private fun requestPermissions() {
        ActivityCompat.requestPermissions(this, arrayOf("Manifest.permission.ACCESS_FINE_LOCATION"),1)
    }

    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if(requestCode == 1) {
            if (permissions[0] == android.Manifest.permission.ACCESS_FINE_LOCATION ) {
                registerLocationListner()
            }
        }
    }