Карта текущего местоположения google

Приложение Gradle применить плагин: 'com.android.application'

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "com.example.david.gas_map"
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        multiDexEnabled true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.2'
    testImplementation 'junit:junit:4.12'
    implementation 'com.google.firebase:firebase-core:16.0.1'
    implementation 'com.android.support:multidex:1.0.3'
    implementation 'com.google.android.gms:play-services-maps:15.0.1'
    implementation 'com.google.maps.android:android-maps-utils:0.5+'
    implementation 'com.google.android.gms:play-services-places:15.0.1'
    implementation "com.google.android.gms:play-services-location:15.0.1"
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

Метод определения местоположения Getdevice, поскольку здесь указывается ошибка по неизвестным причинам

private void getDeviceLocation() {
        /*
         * Get the best and most recent location of the device, which may be null in rare
         * cases when a location is not available.
         */
        try {
            if (mLocationPermissionGranted) {
                Task<Location> locationResult = mFusedLocationProviderClient.getLastLocation();
                locationResult.addOnCompleteListener(this, new OnCompleteListener<Location>() {
                    @Override
                    public void onComplete(@NonNull Task<Location> task) {
      if (task.isSuccessful()) {
                        // Set the map's camera position to the current location of the device.
                        mLastKnownLocation = task.getResult();
                        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(
                                new LatLng(mLastKnownLocation.getLatitude(),
                                        mLastKnownLocation.getLongitude()), DEFAULT_ZOOM));
                    } else if (mLastKnownLocation!=null){
                        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(
                                new LatLng(mLastKnownLocation.getLatitude(),
                                        mLastKnownLocation.getLongitude()), DEFAULT_ZOOM));}

                    else {
                        Log.d(TAG, "Current location is null. Using defaults.");
                        Log.e(TAG, "Exception: %s", task.getException());
                        mMap.moveCamera(CameraUpdateFactory
                                .newLatLngZoom(mDefaultLocation, DEFAULT_ZOOM));
                        mMap.getUiSettings().setMyLocationButtonEnabled(false);
                    }
                }
            });
        }
    } catch (SecurityException e)  {
        Log.e("Exception: %s", e.getMessage());
    }
}

Ошибка

FATAL EXCEPTION: main
              Process: com.example.david.gas_map, PID: 9962
              java.lang.NullPointerException
                  at com.example.david.gas_map.MainActivity$2.onComplete(MainActivity.java:203)
                  at com.google.android.gms.tasks.zzj.run(Unknown Source)
                  at android.os.Handler.handleCallback(Handler.java:733)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:136)
                  at android.app.ActivityThread.main(ActivityThread.java:5479)
                  at java.lang.reflect.Method.invokeNative(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:515)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
                  at dalvik.system.NativeStart.main(Native Method)

Создать

public class MainActivity extends AppCompatActivity implements OnMapReadyCallback{

    private static final String TAG = MainActivity.class.getSimpleName();
    private GoogleMap mMap;
    private CameraPosition mCameraPosition;

    // The entry points to the Places API.
    private GeoDataClient mGeoDataClient;
    private PlaceDetectionClient mPlaceDetectionClient;

    // The entry point to the Fused Location Provider.
    private FusedLocationProviderClient mFusedLocationProviderClient;

    // A default location (Sydney, Australia) and default zoom to use when location permission is
    // not granted.
    private final LatLng mDefaultLocation = new LatLng(-33.8523341, 151.2106085);
    private static final int DEFAULT_ZOOM = 15;
    private static final int PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION = 1;
    private boolean mLocationPermissionGranted;

    // The geographical location where the device is currently located. That is, the last-known
    // location retrieved by the Fused Location Provider.
    private Location mLastKnownLocation;

Я получаю эту ошибку, которая указывает на получение местоположения устройства по неизвестным причинам. Что я делаю не так? Ошибка указывает на эту строку new LatLng (mLastKnownLocation.getLatitude ()

mLastKnownLocation = task.getResult();
                            mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(
                                    new LatLng(mLastKnownLocation.getLatitude(),
                                            mLastKnownLocation.getLongitude()), DEFAULT_ZOOM));