Question

我已经和这个问题坐了很长时间了。我有4个选项卡（ViewPager）第二个选项卡包含一个MapView。当我从第一个或第三个选项卡导航到地图选项卡时，地图显示正常，它会缩放到我的位置并显示标记，但是一旦我从第四个选项卡导航到地图选项卡，它就不会设置。它只显示没有标记或没有缩放的空白地图。当我从标签中打开另一个活动并返回地图时，它也没有设置地图。

任何帮助都将受到赞赏，因为这个问题困扰了我好几个星期：

代码：

MapsAtivity.java

public class MapsActivity extends Fragment implements View.OnClickListener {
private static View view;
static LatLng p1 = null;
private static GoogleMap mMap;
private static String EVENT_LOC_URL = "";
public static Marker me;
public static String names[];
View v;
static Context ctx;
MapView mapView;

public static MapsActivity newInstance(int page, String title) {
    MapsActivity mapsActivity = new MapsActivity();
    Bundle args = new Bundle();
    args.putInt("someInt", page);
    args.putString("someTitle", title);
    mapsActivity.setArguments(args);
    return mapsActivity;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    page = getArguments().getInt("someInt", 0);
    title = getArguments().getString("someTitle");
    ctx = getActivity();
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    view = inflater.inflate(R.layout.activity_maps, container, false);
    mapView = (MapView) view.findViewById(R.id.map);
    mapView.onCreate(savedInstanceState);
    ctx = getActivity();
    setUpMapIfNeeded();
    EVENT_LOC_URL = getResources().getString(R.string.server) + "eventLocations.php";
    FloatingActionButton mLocate = (FloatingActionButton)view.findViewById(R.id.locateme);
    mLocate.setOnClickListener(this);

    return view;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    setUpMapIfNeeded();
    if (mMap != null)
        setUpMap();
}

@Override
public void onResume() {
    mapView.onResume();
    super.onResume();
    if (mMap == null) {
        // Try to obtain the map from the SupportMapFragment.
        setUpMapIfNeeded();
        // Check if we were successful in obtaining the map.
        if (mMap != null)
            setUpMap();
    }
}

/***** Sets up the map if it is possible to do so *****/
public void setUpMapIfNeeded() {
    // Do a null check to confirm that we have not already instantiated the map.
    if (mMap == null) {
        // Try to obtain the map from the SupportMapFragment.
        mMap = mapView.getMap();
        // Check if we were successful in obtaining the map.
        if (mMap != null)
            setUpMap();
    }
}

private void setUpMap() {
    MapsInitializer.initialize(this.getActivity());
    getLongLat gl = new getLongLat(ctx);
    showMyLoc(gl.getLatitude(), gl.getLongitude(), 16);
    me = mMap.addMarker(new MarkerOptions()
            .position(new LatLng(gl.getLatitude(), gl.getLongitude()))
            .title("Current Location")
            .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_BLUE)));

}

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

@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.locateme:
            doLocate();
    }
}


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

    // Remove the map fragment to prevent errors on the next load
    if(mMap != null){
        try {
        Fragment mapFragment = new SupportMapFragment();
            getChildFragmentManager()
                    .beginTransaction()
                    .remove(mapFragment)
                    .commit();
            mMap = null;
        } catch (Exception e){}
    }
}

public void doLocate(){
    me.remove();
    MapsInitializer.initialize(this.getActivity());
    getLongLat gl = new getLongLat(ctx);
    showMyLoc(gl.getLatitude(), gl.getLongitude(), 16);
    me = mMap.addMarker(new MarkerOptions()
            .position(new LatLng(gl.getLatitude(), gl.getLongitude()))
            .title("Current Location")
            .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_BLUE)));

}

private static void showMyLoc(double latitude, double longitude, int i) {
    /////----------------------------------Zooming camera to position user-----------------
    LocationManager locationManager = (LocationManager) ctx.getSystemService(Activity.LOCATION_SERVICE);
    Criteria criteria = new Criteria();

    locationManager.getLastKnownLocation(locationManager.getBestProvider(criteria, false));
    try {
        mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(
                new LatLng(latitude, longitude), 800));

        CameraPosition cameraPosition = new CameraPosition.Builder()
                .target(new LatLng(latitude, longitude))      // Sets the center of the map to location user
                .zoom(i)                   // Sets the zoom
                .bearing(0)                // Sets the orientation of the camera to east
                .tilt(90)                   // Sets the tilt of the camera to 30 degrees
                .build();                   // Creates a CameraPosition from the builder
        mMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));
    } catch (Exception ex) {
        Log.d("Error: ", ex.toString());
        Toast.makeText(ctx, ctx.getString(R.string.error_loading_location), Toast.LENGTH_LONG).show();
    }
}

没有logcat错误或任何我只收到空地图。

Answer 1

我设法通过设置 offscreenpagelimit 并将以下代码添加到 onDestroyView 方法来解决此问题：

@Override
public void onDestroyView(){
    super.onDestroyView();
    Fragment fragment = (getFragmentManager().findFragmentById(R.id.map));
    FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction();
    ft.remove(fragment);
    ft.commitAllowingStateLoss();
}

在 MainActivity.java 中设置了 ViewPager 。我添加了以下代码：

viewPager.setOffscreenPageLimit(11);

选项卡开关上的Android MapView空白

1 个答案: