Question

我尝试在我的应用中实施Google地图。我使用导航抽屉并像这样调用我的片段：

//Main-Class
public void onNavigationDrawerItemSelected(int position) {

    Fragment myFramgent = null;
    switch (position) {
        ...
        case 2 :
            myFramgent = new Fillilaen();
            System.out.println("FILLIAEN");
            break;
        ...
        }
     FragmentManager fragmentManager = getSupportFragmentManager();

     fragmentManager.beginTransaction()
            .replace(R.id.container, myFramgent)
            .commit();
    }

Fillialaen班

    public class Fillilaen extends SupportMapFragment implements ... {

    private GoogleMap mMap;

      public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         myView = inflater.inflate(R.layout.fillialen2, container, false);
         return myView;
      }

     @Override
     public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
      super.onViewCreated(view, savedInstanceState);
       SupportMapFragment fragment = (SupportMapFragment) this.getChildFragmentManager().findFragmentById(R.id.location_map);
       fragment.getMapAsync(this); //ERROR COMES HERE
       }

       public void onMapReady(GoogleMap googleMap) {
       //never enter this..
       mMap = googleMap;
       Marker hamburg = mMap.addMarker(new MarkerOptions().position(HAMBURG).title("Hamburg"));
       }
    }

我的XML

<fragment
    android:id="@+id/location_map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    class="com.google.android.gms.maps.SupportMapFragment" />

我收到了NullPointerException，我绝对不知道为什么。我搜索了很多并发现了类似的问题，但没有任何帮助。

Nullpointer异常的开始：

致命的例外：主要过程：roth.com.test6，PID：13097 java.lang.NullPointerException：尝试在null对象引用上调用接口方法'void com.google.maps.api.android.lib6.e.fl.o（）' 在com.google.maps.api.android.lib6.e.y.b（未知来源）....

谢谢！

Answer 1

您正在尝试将SupportMapFragment嵌套在外部SupportMapFragment中。

如果您的Fragment扩展了SupportMapFragment，则无需对任何布局xml进行扩充，您只需调用this.getMapAsync()，因为this指的是SupportMapFragment：

public class MyMapFragment extends SupportMapFragment 
                                    implements OnMapReadyCallback {

    private GoogleMap mMap;
    private Marker marker;


    public MyMapFragment () {
    }

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

        setUpMapIfNeeded();
    }

    private void setUpMapIfNeeded() {

        if (mMap == null) {
            //"this" is a SupportMapFragment,
            //and "this" implements OnMapReadyCallback
            // so you can call this.getMapAsync(this) here:
            getMapAsync(this);
        }
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {

        mMap = googleMap;
        setUpMap();
    }

    private void setUpMap() {

        mMap.setMyLocationEnabled(true);
        mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);


        mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {

            @Override
            public void onMapClick(LatLng point) {

                //remove previously placed Marker
                if (marker != null) {
                    marker.remove();
                }

                //place marker where user just clicked
                marker = mMap.addMarker(new MarkerOptions().position(point).title("Marker")
                        .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA)));

            }
        });

    }

}

导航抽屉中的Google地图 - Nullpointer异常，这是正确的片段吗？

1 个答案: