title: MapView.onMapReady never called in Fragment for load Google Map in MapView
body: <p>I'll try to show a map in my Android application on a fragment named <code>RoeteFragment</code>. If I debug my code I see that the method <code>onMapReady</code> is never called so that the map will not load.</p>
  
  <p>The fragment implements <code>OnMapReadyCallback</code> like needed and in the <code>onCreateView</code> I get the <code>MapView</code> and call <code>getMapAsync</code>. If I place a breakpoint on that method, it will always been hit, the breakpoint inside <code>onMapReady</code> never been hit. There is no exception thrown.</p>
  
  <p>I've also a valid Google Maps API key in the file <code>res/values/google_maps_api.xml</code>.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="match_parent"&gt;
  
      &lt;com.google.android.gms.maps.MapView
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:id="@+id/map" /&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  
  
  <pre><code>public class RoeteFragment extends Fragment implements OnMapReadyCallback {
  
      private MapView mapView;
      private static Roete _roete;
  
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
      }
  
      @Override
      public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
          View view = inflater.inflate(R.layout.fragment_roete, container, false);
          mapView = (MapView) view.findViewById(R.id.map);
          mapView.getMapAsync(this);
          return view;
      }
  
      @Override
      public void onMapReady(GoogleMap googleMap) {
  
          if (_roete != null &amp;&amp; _roete.getAankomstLocatie() != null &amp;&amp; _roete.getVertrekLocatie() != null) {
              LatLng aankomst = new LatLng(_roete.getAankomstLocatie().getLatitude(), _roete.getAankomstLocatie().getLongitude());
              googleMap.addMarker(new MarkerOptions().position(aankomst).title("aankomst"));
              googleMap.moveCamera(CameraUpdateFactory.newLatLng(aankomst));
  
              LatLng vertrek = new LatLng(_roete.getVertrekLocatie().getLatitude(), _roete.getVertrekLocatie().getLongitude());
              googleMap.addMarker(new MarkerOptions().position(vertrek).title("vertrek"));
              googleMap.moveCamera(CameraUpdateFactory.newLatLng(vertrek));
          }
      }
  
      public static Fragment newInstance() {
          return new RoeteFragment ();
      }
  
      public static Fragment newInstance(Roete roete) {
          _roete = roete;
          return newInstance();
      }
  }
  </code></pre>
  
  <p>Could you file the bug in my code?</p>