创建地图v2扩展片段时出错

Question

I tried to implement google map v2 on fragment..Here is the code :

package com.example.tropo;
public class D_Map extends Fragment {
    public static final String TAG = "map";
    MapView mapView;
    GoogleMap map;

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

    // Gets the MapView from the XML layout and creates it
    mapView = (MapView) v.findViewById(R.id.mapview);
    mapView.onCreate(savedInstanceState);

    // Gets to GoogleMap from the MapView and does initialization stuff
    map = mapView.getMap();
    map.getUiSettings().setMyLocationButtonEnabled(false);
    map.setMyLocationEnabled(true);

    // Needs to call MapsInitializer before doing any CameraUpdateFactory calls
    try {
        MapsInitializer.initialize(this.getActivity());
    } catch (Exception e) {
        e.printStackTrace();
    }

    // Updates the location and zoom of the MapView
    CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(new LatLng(43.1, -87.9), 10);
    map.animateCamera(cameraUpdate);

    return v;
}

@Override
public void onResume() {
    mapView.onResume();
    super.onResume();
}

@Override
public void onDestroy() {
    super.onDestroy();
    mapView.onDestroy();
}

@Override
public void onLowMemory() {
    super.onLowMemory();
    mapView.onLowMemory();
}

}

logcat:

07-08 04:08:08.590  21776-21776/com.myapps.materialapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.NullPointerException
            at com.example.tropo.D_Map.onCreateView(D_Map.java:49)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:829)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1035)
            at android.app.BackStackRecord.run(BackStackRecord.java:635)
            at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1397)
            at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
            at android.os.Handler.handleCallback(Handler.java:615)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4745)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

In Google Play services 6.5 and per the MapFragment documentation :

A GoogleMap must be acquired using getMapAsync(OnMapReadyCallback) . This class automatically initializes the maps system and the view.

Use that callback rather than getMap() to ensure that the map is not null .

Answer 2

getMap is deprecated.Use getMapAsync(OnMapReadyCallback) instead. The callback method provides you with a GoogleMap instance guaranteed to be non-null and ready to be used.

Also,

getmap returns Null if the view of the map is not yet ready. This can happen when Google Play services is not available. If Google Play services becomes available afterwards, calling this method again will initialize and return the GoogleMap.

https://developers.google.com/android/reference/com/google/android/gms/maps/MapView

Try using the SupportMapFragment.Add it to your activity layout

<fragment
        android:id="@+id/map"
        android:name="com.google.android.gms.maps.SupportMapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MapsActivity"
        tools:layout="@layout/abc_activity_chooser_view" />

get map in the activity using

GoogleMap mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                    .getMap();