在SupportMapFragment中引用MapView

Question

我有一个扩展了SupportMapFragment的Fragment。

public class PlaceMapsFragment extends SupportMapFragment {
    private GoogleMap mMap;
    private LatLng mPosFija;

    public PlaceMapsFragment() {
        super();
    }

    public static PlaceMapsFragment newInstance(LatLng posicion) {
        PlaceMapsFragment frag = new PlaceMapsFragment();
        frag.mPosFija = posicion;
        return frag;
    }

    @Override
    public GoogleMap getMap() {
        // TODO Auto-generated method stub
        return super.getMap();
    }

    @Override
    public void onCreate(Bundle arg0) {
        // TODO Auto-generated method stub
        super.onCreate(arg0);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = super.onCreateView(inflater, container, savedInstanceState);
        //initMap();
        return view;
    }

    private void initMap() {
        UiSettings settings = getMap().getUiSettings();
        settings.setAllGesturesEnabled(false);
        settings.setMyLocationButtonEnabled(false);

        getMap().moveCamera(CameraUpdateFactory.newLatLngZoom(mPosFija, 16));
        getMap().addMarker(
                new MarkerOptions().position(mPosFija)
                        .icon(BitmapDescriptorFactory
                                .fromResource(R.drawable.marker)));
    }

}

现在我想引用自动生成的MapView，以便我可以向地图添加我的功能。

当我尝试initMap();时，我会得到NullPointerException。

错误：

12-10 02:54:20.171: E/AndroidRuntime(4339): FATAL EXCEPTION: main
12-10 02:54:20.171: E/AndroidRuntime(4339): java.lang.NullPointerException
12-10 02:54:20.171: E/AndroidRuntime(4339):     at maps.ar.b.a(Unknown Source)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at maps.y.h.a(Unknown Source)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at maps.y.au.a(Unknown Source)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at maps.y.ae.moveCamera(Unknown Source)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at com.google.android.gms.maps.internal.IGoogleMapDelegate$Stub.onTransact(IGoogleMapDelegate.java:83)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.os.Binder.transact(Binder.java:297)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at com.google.android.gms.maps.internal.IGoogleMapDelegate$a$a.moveCamera(Unknown Source)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at com.google.android.gms.maps.GoogleMap.moveCamera(Unknown Source)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at com.m7.nomad.PlaceMapsFragment.initMap(PlaceMapsFragment.java:55)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at com.m7.nomad.PlaceMapsFragment.onCreateView(PlaceMapsFragment.java:46)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.support.v4.app.Fragment.performCreateView(Fragment.java:1460)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:911)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:461)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at com.m7.nomad.PlaceActivity$TabManager.onTabChanged(PlaceActivity.java:153)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.widget.TabHost.invokeOnTabChangeListener(TabHost.java:379)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.widget.TabHost.setCurrentTab(TabHost.java:364)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.widget.TabHost$2.onTabSelectionChanged(TabHost.java:150)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.widget.TabWidget$TabClickListener.onClick(TabWidget.java:540)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.view.View.performClick(View.java:3591)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.view.View$PerformClick.run(View.java:14263)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.os.Handler.handleCallback(Handler.java:605)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.os.Handler.dispatchMessage(Handler.java:92)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.os.Looper.loop(Looper.java:137)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at android.app.ActivityThread.main(ActivityThread.java:4507)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at java.lang.reflect.Method.invokeNative(Native Method)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at java.lang.reflect.Method.invoke(Method.java:511)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
12-10 02:54:20.171: E/AndroidRuntime(4339):     at dalvik.system.NativeStart.main(Native Method)

- Harsha M V

---

你解决了这个错误吗？我也遇到了同样的问题 :S - ƒernando Valle

Answer 1

这是一种预期的行为。

只有在Fragment经历了onCreateView()之后，才能调用getMap()，否则它将返回null。如果Google Play服务不可用，也可能会返回null。

换句话说，在onResume()中调用initMap()。

您可以在这里查看更多信息。

希望对您有所帮助！

- Tudor Luca

Answer 2

我终于解决了它，您不必覆盖 getMap() 且不需要使用 mMap 变量，因为 GoogleMap 已经包含在该类中。最后，在 onResume() 中需要调用 initMap()：

public class PlaceMapsFragment extends SupportMapFragment {
    private LatLng mPosFija = new LatLng(37.878901,-4.779396);

    public PlaceMapsFragment() {
        super();
    }

    public static PlaceMapsFragment newInstance(LatLng posicion) {
        PlaceMapsFragment frag = new PlaceMapsFragment();
        frag.mPosFija = posicion;
        return frag;
    }

   @Override
   public void onResume() {
    // TODO Auto-generated method stub
    super.onResume();
    initMap();
   }



    @Override
    public void onCreate(Bundle arg0) {
        // TODO Auto-generated method stub
        super.onCreate(arg0);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = super.onCreateView(inflater, container, savedInstanceState);
        //initMap();
        return view;
    }

    private void initMap() {
        UiSettings settings = getMap().getUiSettings();
        settings.setAllGesturesEnabled(false);
        settings.setMyLocationButtonEnabled(false);

        getMap().moveCamera(CameraUpdateFactory.newLatLngZoom(mPosFija, 16));
        getMap().addMarker(
                new MarkerOptions().position(mPosFija)
                        .icon(BitmapDescriptorFactory
                                .fromResource(R.drawable.marker)));
    }

}

希望这对于像我一样开始使用google maps api的人有所帮助（开心 :D）。

- ƒernando Valle

Answer 3

问题出在onCreateView方法中。你忘记调用super.onCreateView()了。请检查this。

- JoseF