Question

当应用程序运行时总是返回NULL异常
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.MapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference

     if (map == null) {
    MapFragment mapFragment = (MapFragment) getFragmentManager()
            .findFragmentById(R.id.map);
    mapFragment.getMapAsync(new OnMapReadyCallback() {

        @Override
        public void onMapReady(GoogleMap googlemap) {
            // TODO Auto-generated method stub
            map=googlemap;
           // startMap();
        }
    });
}

Xml代码在这里我使用Map *

                <fragment
                    android:id="@+id/map"
                    class="com.shahi.driver.locationfiles.TouchableMapFragment"
                    android:layout_width="fill_parent"
                    android:layout_height="fill_parent" />

Answer 1

您的类将是：

 <a href="http://localhost:9999/video.mp4" download> Dowload Video </a>

和 your_layout.xml 将是：

public class YourActivity extends Activity implements OnMapReadyCallback {

    @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.your_layout);
            try {
                // Loading map
               MapFragment mapFragment = (MapFragment) getFragmentManager().findFragmentById(R.id.map);
                mapFragment.getMapAsync(this);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

    @Override
        protected void onResume() {
            super.onResume();
            MapFragment mapFragment = (MapFragment) getFragmentManager().findFragmentById(R.id.map);
                mapFragment.getMapAsync(this);
        }

    @Override
        public void onMapReady(final GoogleMap googleMap) {
            final LatLng current_position = new LatLng(your_latitude, your_longitude);
            MarkerOptions marker = new MarkerOptions().position(current_position).title("Your Address").snippet("Anything");
            googleMap.addMarker(marker);
            googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(current_position, 12));
            googleMap.getUiSettings().setMapToolbarEnabled(true);
            googleMap.setMyLocationEnabled(true);
        }
    }

Answer 2

这应该有效：

private GoogleMap mMap;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);

    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);

}

@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;

    // Add a marker in Sydney and move the camera
        LatLng location = new LatLng(latitude, longitude);
        mMap.addMarker(new MarkerOptions().position(location ).title("Marker in location "));
        mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));

}

}

然后你的xml：

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/map"
    android:name="com.google.android.gms.maps.SupportMapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.polaris.project_x.MapsActivity" />

Answer 3

我可以看到你在XML代码上使用了自定义Map Fragment。通过搜索它的名字，我偶然发现它在GitHub上的代码。

您的代码的问题在于您尝试从布局中获取MapFragment，但您的自定义地图代码正在扩展SupportMapFragment。

因此，要使代码工作，请将MapFragment更改为SupportMapFragment。

 SupportMapFragment mapFragment = (SupportMapFragment) getFragmentManager()
        .findFragmentById(R.id.map);

此外，如果您的BaseActivity正在扩展AppCompatActivity，那么请使用getSupportFragmentManager（）而不是getFragmentManager（）。

映射返回NULL

3 个答案: