Question

我尝试在片段上实现谷歌地图v2。这是代码：

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的：

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

Google Play services 6.5和MapFragment documentation：

必须使用getMapAsync(OnMapReadyCallback)获取GoogleMap。该类自动初始化地图系统和视图。

使用该回调而不是getMap()来确保地图不是null。

Answer 2

不推荐使用getMap。请改用getMapAsync（OnMapReadyCallback）。回调方法为您提供了一个保证非空并准备好使用的GoogleMap实例。

此外，

如果地图视图尚未准备好，

getmap将返回Null。当Google Play服务不可用时，就会发生这种情况。如果之后Google Play服务可用，则再次调用此方法将初始化并返回GoogleMap。

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

尝试使用SupportMapFragment。将其添加到您的活动布局

<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" />

使用

在活动中获取地图

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

创建map v2扩展片段时出错

2 个答案: