Display Speed in MPH

Speedometer.kt

package com.greenrobot.speedometer

import android.Manifest
import android.annotation.SuppressLint
import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import com.google.android.gms.location.LocationCallback
import com.google.android.gms.location.LocationRequest
import com.google.android.gms.location.LocationResult
import com.google.android.gms.location.LocationServices
import com.karumi.dexter.Dexter
import com.karumi.dexter.PermissionToken
import com.karumi.dexter.listener.PermissionDeniedResponse
import com.karumi.dexter.listener.PermissionGrantedResponse
import com.karumi.dexter.listener.PermissionRequest
import com.karumi.dexter.listener.single.PermissionListener
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {
    private val UPDATE_INTERVAL = (10 * 1000).toLong()  /* 10 secs */
    private val FASTEST_INTERVAL: Long = 2000 /* 2 sec */
    private lateinit var locationCallback: LocationCallback
    val metersPerSecondToMilesPerHour = 2.23694;

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        locationCallback = object : LocationCallback() {
            override fun onLocationResult(locationResult: LocationResult?) {
                locationResult ?: return
                for (location in locationResult.locations){
                    val mphSpeed = metersPerSecondToMilesPerHour * location.speed
                    mph.setText(mphSpeed.toString());

                }
            }
        }

        askForPermission();

    }


    fun askForPermission() {

        Dexter.withActivity(this)
            .withPermission(Manifest.permission.ACCESS_FINE_LOCATION)
            .withListener(object : PermissionListener {
                @SuppressLint("MissingPermission")
                override fun onPermissionGranted(response: PermissionGrantedResponse) {
                    val locationRequest = LocationRequest()
                    locationRequest.priority = LocationRequest.PRIORITY_HIGH_ACCURACY
                    locationRequest.interval = UPDATE_INTERVAL
                    locationRequest.fastestInterval = FASTEST_INTERVAL
                    val fusedLocationClient = LocationServices.getFusedLocationProviderClient(this@MainActivity)
                    fusedLocationClient.requestLocationUpdates(locationRequest, locationCallback, null)
                }

                override fun onPermissionDenied(response: PermissionDeniedResponse) {

                }

                override fun onPermissionRationaleShouldBeShown(
                    permission: PermissionRequest,
                    token: PermissionToken
                )
                {
                }

            }).check()
    }
}