安卓 map 扩展 : return map as null

Question

我正在开发使用 Android map 扩展库的 Android 应用程序。当尝试从 mapFragment 获取 map 时，我得到的 map 为 null。我验证了我的 mapFragment 不为空。以下是我的 fragment 。

public class ClusterMarkersFragment extends Fragment {

private static final String LOG_AREA = "ClusterMarkersFragment";
public static final String KEY_PREFIX = "KeyPrefix";

private SupportMapFragment mapFragment;
public GoogleMap map;

public static ClusterMarkersFragment newInstance (String prefix) {
    ClusterMarkersFragment clusterMarkersFragment = new
        ClusterMarkersFragment();
    Bundle bundle = new Bundle();
    bundle.putString(KEY_PREFIX, prefix);
    clusterMarkersFragment.setArguments(bundle);
    return clusterMarkersFragment;
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    super.onCreateView(inflater, container, savedInstanceState);
    View view = inflater.inflate(R.layout.fragment_cluster_marker,
                                 container, false);

    FragmentManager fm = getChildFragmentManager();

    mapFragment = (SupportMapFragment) fm.findFragmentById(R.id.map_container);
    if (mapFragment == null) {
        mapFragment = SupportMapFragment.newInstance();
        FragmentTransaction tx = fm.beginTransaction();
        tx.add(R.id.map_container, mapFragment);
        tx.commit();
    }

    map = mapFragment.getExtendedMap();

    String prefix = getArguments().getString(KEY_PREFIX);

    getLatLngFromDatabase(prefix);

    map.setClustering(new ClusteringSettings().clusterOptionsProvider(new ClusterOptionsProvider() {
        @Override
        public ClusterOptions getClusterOptions(List<Marker> markers) {
            float hue = BitmapDescriptorFactory.HUE_ROSE;
            BitmapDescriptor blueIcon = BitmapDescriptorFactory.defaultMarker(hue);
            return new ClusterOptions().icon(blueIcon);
        }
    }));

    return view;
}

public void getLatLngFromDatabase (final String prefix) {
    final List<LatLngPair> latLngPairs ;
    //return LatLngPairs from database

    addMarkersOnMap(latLngPairs);
}

private void addMarkersOnMap(final List<LatLngPair> latLngPairs) {

    int diameter = (int) latLngPairs.get(0).rad * 2;
    Bitmap bm = Bitmap.createBitmap(diameter, diameter, Bitmap.Config.ALPHA_8);
    Canvas canvas = new Canvas(bm);
    Paint p = new Paint();

    p.setColor(getResources().getColor(R.color.green));
    canvas.drawCircle(diameter / 2, diameter / 2, diameter / 2, p);

    Bitmap bmIcon = BitmapFactory.decodeResource(getResources(), R.drawable.map_marker);
    canvas.drawBitmap(bmIcon, diameter / 2, diameter / 2, p);

    for (LatLngPair latLngPair : latLngPairs) {
        map.addMarker(new MarkerOptions().position(new LatLng(
            latLngPair.lat, latLngPair.lng)).icon(BitmapDescriptorFactory.
                                                                   fromBitmap(bm)));
    }
}
}

下面是我的布局文件

    <RelativeLayout
android:id="@+id/map_container"
android:layout_width="match_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android" >

Answer 1

只使用异步方法

mapFragment.getExtendedMapAsync(new OnMapReadyCallback() {
    public void onMapReady(GoogleMap googleMap) {
       mMap = googleMap; setUpMap(); 
    } 
});