在选项卡式 android 应用程序中获取 google 地图

Question

我花了一段时间试图让它工作，但在每个教程中我总是卡在某个地方。简而言之，我正在尝试制作一个选项卡式应用程序，其中一个选项卡是 google 映射。

我已经修正了所有常见的错误：

我已经通过SDK下载了所有相关的东西。我有一个 API 键。我添加了 compile com.google.android.gms:play-services:7.5.0 to my dependencies.

我正在尝试跟随this code，但它对我来说并不完全有效，所以我稍微改变了它，但我仍然运行撞墙了。

我当前的错误是java.lang.NullPointerException: IBitmapDescriptorFactory is not initialized。我认为这会在 getMapAsync.

中初始化

这是我的 java 代码：

public class MapFragment extends Fragment{

    MapView mMapView;
    private GoogleMap googleMap;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // inflat and return the layout
        View v = inflater.inflate(R.layout.fragment_location_info, container,
                false);

        mMapView = (MapView) v.findViewById(R.id.mapView);
        mMapView.onCreate(savedInstanceState);

        mMapView.onResume();// needed to get the map to display immediately

        mMapView.getMapAsync(new OnMapReadyCallback() {
            @Override
            public void onMapReady(GoogleMap googleMap) {
                MapsInitializer.initialize(getApplicationContext());
                // latitude and longitude
                double latitude = 17.385044;
                double longitude = 78.486671;


                // create marker
                MarkerOptions marker = new MarkerOptions().position(new LatLng(latitude, longitude)).title("Hello Maps");

                // Changing marker icon
                marker.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_ROSE));
            }
        });

        //MapsInitializer.initialize(getApplicationContext());

        googleMap = mMapView.getMap();
        // latitude and longitude
        double latitude = 17.385044;
        double longitude = 78.486671;


        // create marker
        MarkerOptions marker = new MarkerOptions().position(new LatLng(latitude, longitude)).title("Hello Maps");

        // Changing marker icon
        marker.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_ROSE));

        // adding marker
        googleMap.addMarker(marker);

        CameraPosition cameraPosition = new CameraPosition.Builder().target(new LatLng(17.385044, 78.486671)).zoom(12).build();

        googleMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));

        // Perform any camera updates here
        return v;
    }

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

    @Override
    public void onPause() {
        super.onPause();
        mMapView.onPause();
    }

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

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

Answer 1

您的代码似乎正在进行转换。您正在调用 getMapAsync() 和 getMap()。

只需使用 getMapAsync()，在收到 onMapReady() 回调之前不要对地图进行任何操作。

此外，您不需要 MapsInitializer。来自文档：

Use this class to initialize the Google Maps Android API if features need to be used before obtaining a map. It must be called because some classes such as BitmapDescriptorFactory and CameraUpdateFactory need to be initialized.

If you are using MapFragment or MapView and have already obtained a (non-null) GoogleMap by calling getMap() on either of these classes, then you do not need to worry about this class. See the sample application for some examples.

这里是你的代码修正了一点：

public class MapFragment extends Fragment implements OnMapReadyCallback {

        MapView mMapView;
        private GoogleMap googleMap;

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            // inflate and return the layout
            View v = inflater.inflate(R.layout.fragment_location_info, container,
                    false);

            mMapView = (MapView) v.findViewById(R.id.mapView);
            mMapView.onCreate(savedInstanceState);

            //mMapView.onResume(); // should not be needed

            mMapView.getMapAsync(this);

            //MapsInitializer.initialize(getApplicationContext());

            // Perform any camera updates here
            return v;
        }

        @Override
        public void onMapReady(GoogleMap gMap) {

            googleMap = gMap;

            mMapView.onResume(); //call this here if you really need to

            //MapsInitializer.initialize(getApplicationContext());
            // latitude and longitude
            double latitude = 17.385044;
            double longitude = 78.486671;

            // create marker
            MarkerOptions marker = new MarkerOptions().position(new LatLng(latitude, longitude)).title("Hello Maps");

            // Changing marker icon
            marker.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_ROSE));

            // adding marker
            googleMap.addMarker(marker);

            CameraPosition cameraPosition = new CameraPosition.Builder().target(new LatLng(17.385044, 78.486671)).zoom(12).build();

            googleMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));

        }
   //.........................

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