如何在片段中显示谷歌地图

Question

我有一个ActionBar.NAVIGATION_MODE_TABS的布局。第一个选项卡用于在列表视图中显示结果，第二个选项卡用于在地图中显示结果。在我升级到最新版本的Google Play服务库之前，一切都很好。

此处为用于显示地图的片段：

 public class PlaceMapFragment extends Fragment {
    MapView mapView;
GoogleMap map;
ResultsListener mCallback;
List<Place> places;
private HashMap<String, Place> placeMarker = new HashMap<String, Place>();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    places = mCallback.getPlaces();
    View rootView = inflater.inflate(R.layout.mapview, container, false);
    mapView = (MapView) rootView.findViewById(R.id.mapview);
    mapView.onCreate(savedInstanceState);
    map = mapView.getMap();
    setUpMap();
    return rootView;
}
private void setUpMap() {
    map.getUiSettings().setMyLocationButtonEnabled(true); 
    map.setMyLocationEnabled(true);
    /*
    try { 
        MapsInitializer.initialize(this.getActivity());
    } catch (GooglePlayServicesNotAvailableException e) {
        e.printStackTrace();
    }
    */
   // add markers
}
@Override 
public void onResume() { 
    mapView.onResume();
    super.onResume();
    setUpMap();
}
@Override 
public void onPause() { 
   mapView.onPause();
   super.onPause();
}
@Override
public void onDestroy() {
    mapView.onDestroy();
    super.onDestroy();
}
@Override
public void onLowMemory() {
    super.onLowMemory();
    mapView.onLowMemory();
}
@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    mapView.onSaveInstanceState(outState);
}
public interface ResultsListener {
    public List<Place> getPlaces();
}
@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    // This makes sure that the container activity has implemented
    // the callback interface. If not, it throws an exception
    try {
        mCallback = (ResultsListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString() + " must implement ResultsListener");
    }
}
}

我收到这些错误：

04-05 03:58:22.040: E/AndroidRuntime(661): FATAL EXCEPTION: main
04-05 03:58:22.040: E/AndroidRuntime(661): java.lang.NullPointerException
04-05 03:58:22.040: E/AndroidRuntime(661):  at com.tomsyweb.mapslee.fragments.PlaceMapFragment.setUpMap(PlaceMapFragment.java:54)
04-05 03:58:22.040: E/AndroidRuntime(661):  at com.tomsyweb.mapslee.fragments.PlaceMapFragment.onCreateView(PlaceMapFragment.java:48)

我已经评论了MapsInitializer.initialize(this.getActivity());部分，因为GooglePlayServicesNotAvailableException给出了错误。

地图视图.xml

<com.google.android.gms.maps.MapView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/mapview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

我的代码取自使用ActionBar选项卡在onCreateView中获取Google地图片段

Answer 1

如果设备未安装最新版本的地图，或者可能出于其他原因，您的地图可能为 null。 尝试创建它甚至可能提示用户启动其他活动以更新其设备。 所以建议创建一个这样的initMap()方法，并在你的onCreate(...)和onResume()中调用它：

private void initMap() {
   if(map == null) {
      map = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
      if(map != null) {
         // set up map
      }
   }
}