onLocationResult在请求位置后从未调用

我试图获得我的设备在碎片中的最后一个已知位置:

显示

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

定义

private lateinit var fusedLocationClient: FusedLocationProviderClient
private lateinit var mLocationRequest: LocationRequest
private var location: Location? = null

一次创建

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

    fusedLocationClient = LocationServices.getFusedLocationProviderClient(context as MainActivity)
    mLocationRequest = LocationRequest()
    mLocationRequest.interval = 120000
    mLocationRequest.fastestInterval = 120000
    mLocationRequest.priority = LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY
    mLocationRequest.numUpdates = 1
}

请求位置

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View?
{
    // Inflate the layout for this fragment
    val view = inflater.inflate(R.layout.fragment_product_add, container, false)

    view.button_add_product.setOnClickListener(this)
    view.button_photo.setOnClickListener(this)

    if (ContextCompat.checkSelfPermission(view.context, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED)
    {
        fusedLocationClient.requestLocationUpdates(mLocationRequest, locationCallback, Looper.myLooper())
    }
    else
    {
        ActivityCompat.requestPermissions(this.context as MainActivity, arrayOf(Manifest.permission.ACCESS_FINE_LOCATION), REQUEST_LOCATION_PERMISSION)
    }

    return view
}

获取位置

private val locationCallback: LocationCallback? = object : LocationCallback()
{
    override fun onLocationResult(loc: LocationResult?)
    {
        super.onLocationResult(loc)
        val locations = loc?.locations
        if (locations != null)
        {
            val lastLocation = locations[locations.size - 1]
            location = lastLocation
            product_coordinates.setText("Lat:${location?.latitude} Lon:${location?.longitude}")
            fusedLocationClient.removeLocationUpdates(this)
        }
    }
}

locationCallback中的代码永远不会执行。

我也试过下面的代码,但是 location 总是 null :

fusedLocationClient.lastLocation.addOnSuccessListener(context as MainActivity) { location ->
    if (location != null) {
        product_coordinates.setText("Lat:${location.latitude} Lon:${location.longitude}")
    }
}