使用Maps API v2以编程方式初始化MapFragment

Question

我正在尝试将MapFragment添加到我当前的Fragment中.嵌套片段的使用仅限于FragmentTransactions,您不能在布局中使用xml标记.此外,我希望在用户按下按钮时将其添加到主片段中.所以,getInstance()当用户按下该按钮并将其添加到适当的位置时,我将以编程方式创建MapFragment .它显示正确,到目前为止一切顺利.

问题是在附加MapFragment之后我需要获得一个GoogleMap 放置Marker的引用,但是该getMap()方法返回null(因为片段onCreateView()还没有被调用).

我查看了演示示例代码,我发现他们使用的解决方案是初始化MapFragment onCreate()并在调用onResume()之后获取对GoogleMap的引用onCreateView().

我需要在MapFragment初始化之后立即获取对GoogleMap的引用,因为我希望用户能够使用按钮显示或隐藏地图.我知道一个可能的解决方案是如上所述在开始时创建Map并且只是设置它的可见性消失了,但我希望默认情况下关闭地图,这样如果没有明确要求它就不会占用用户的带宽为了它.

我试过了MapsInitializer,但也没用.我有点卡住了.有任何想法吗？这是我到目前为止的测试代码:

public class ParadaInfoFragment extends BaseDBFragment {
// BaseDBFragment is just a SherlockFragment with custom utility methods.

private static final String MAP_FRAGMENT_TAG = "map";
private GoogleMap mMap;
private SupportMapFragment mMapFragment;
private TextView mToggleMapa;
private boolean isMapVisible = false;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment_parada_info, container, false);
    mToggleMapa = (TextView) v.findViewById(R.id.parada_info_map_button);
    return v;
}

@Override
public void onStart() {
    super.onStart();
    mToggleMapa.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (!isMapVisible) {
                openMap();
            } else {
                closeMap();
            }
            isMapVisible = !isMapVisible;
        }
    });
}

private void openMap() {
    // Creates initial configuration for the map
    GoogleMapOptions options = new GoogleMapOptions().camera(CameraPosition.fromLatLngZoom(new LatLng(37.4005502611301, -5.98233461380005), 16))
            .compassEnabled(false).mapType(GoogleMap.MAP_TYPE_NORMAL).rotateGesturesEnabled(false).scrollGesturesEnabled(false).tiltGesturesEnabled(false)
            .zoomControlsEnabled(false).zoomGesturesEnabled(false);

    // Modified from the sample code:
    // It isn't possible to set a fragment's id programmatically so we set a
    // tag instead and search for it using that.
    mMapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentByTag(MAP_FRAGMENT_TAG);

    // We only create a fragment if it doesn't already exist.
    if (mMapFragment == null) {
        // To programmatically add the map, we first create a
        // SupportMapFragment.
        mMapFragment = SupportMapFragment.newInstance(options);
        // Then we add it using a FragmentTransaction.
        FragmentTransaction fragmentTransaction = getChildFragmentManager().beginTransaction();
        fragmentTransaction.add(R.id.parada_info_map_container, mMapFragment, MAP_FRAGMENT_TAG);
        fragmentTransaction.commit();
    }
    // We can't be guaranteed that the map is available because Google Play
    // services might not be available.
    setUpMapIfNeeded(); //XXX Here, getMap() returns null so  the Marker can't be added
    // The map is shown with the previous options.
}

private void closeMap() {
    FragmentTransaction fragmentTransaction = getChildFragmentManager().beginTransaction();
    fragmentTransaction.remove(mMapFragment);
    fragmentTransaction.commit();
}

private 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 = mMapFragment.getMap();
        // Check if we were successful in obtaining the map.
        if (mMap != null) {
            mMap.addMarker(new MarkerOptions().position(new LatLng(37.4005502611301, -5.98233461380005)).title("Marker"));
        }
    }
}
}

谢谢

Answer 1

好的AnderWebs在Google+上给了我一个答案,但他太懒了......呃忙着再写这里,所以这里是简短的版本:扩展MapFragment课程并覆盖onCreateView()方法.完成此方法后,我们可以获得对que GoogleMap对象的非null引用.

这是我特别的解决方案:

public class MiniMapFragment extends SupportMapFragment {
    private LatLng mPosFija;

    public MiniMapFragment() {
        super();
    }

    public static MiniMapFragment newInstance(LatLng posicion){
        MiniMapFragment frag = new MiniMapFragment();
        frag.mPosFija = posicion;
        return frag;
    }

    @Override
    public View onCreateView(LayoutInflater arg0, ViewGroup arg1, Bundle arg2) {
        View v = super.onCreateView(arg0, arg1, arg2);
        initMap();
        return v;
    }

    private void initMap(){
        UiSettings settings = getMap().getUiSettings();
        settings.setAllGesturesEnabled(false);
        settings.setMyLocationButtonEnabled(false);

        getMap().moveCamera(CameraUpdateFactory.newLatLngZoom(mPosFija,16));
        getMap().addMarker(new MarkerOptions().position(mPosFija).icon(BitmapDescriptorFactory.fromResource(R.drawable.marker)));
    }
}

现在在我之前的Fragment类中

mMapFragment = MiniMapFragment.newInstance(new LatLng(37.4005502611301, -5.98233461380005));

也许它还不完美,因为在显示地图时屏幕会闪烁.但不确定问题是由于这个还是其他原因.

Answer 2

谢谢,发现这非常有帮助.我发布了我稍微修改过的解决方案,因为在地图准备就绪时告诉父片段更清晰.此方法也适用于saveInstanceState/restoreInstanceState循环.

public class CustomMapFragment extends SupportMapFragment {

    private static final String LOG_TAG = "CustomMapFragment";

    public CustomMapFragment() {
        super();

    }

    public static CustomMapFragment newInstance() {
        CustomMapFragment fragment = new CustomMapFragment();
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater arg0, ViewGroup arg1, Bundle arg2) {
        View v = super.onCreateView(arg0, arg1, arg2);
        Fragment fragment = getParentFragment();
        if (fragment != null && fragment instanceof OnMapReadyListener) {
            ((OnMapReadyListener) fragment).onMapReady();
        }
        return v;
    }



    /**
     * Listener interface to tell when the map is ready
     */
    public static interface OnMapReadyListener {

        void onMapReady();
    }
}

要用作嵌套片段: -

public class ParentFragment extends Fragment implements OnMapReadyListener {

    ...

    mMapFragment = CustomMapFragment.newInstance();
    getChildFragmentManager().beginTransaction().replace(R.id.mapContainer, mMapFragment).commit();

    @Override
    public void onMapReady() {
        mMap = mMapFragment.getMap();
    }
    ...
}

希望它可以帮助某人.

Answer 3

这是我的解决方案,我从以前发布的代码中获取灵感并进行了清理.我还添加了带有和不带有GoogleMapOptions参数的静态方法.

public class GoogleMapFragment extends SupportMapFragment {

    private static final String SUPPORT_MAP_BUNDLE_KEY = "MapOptions";

    public static interface OnGoogleMapFragmentListener {
        void onMapReady(GoogleMap map);
    }

    public static GoogleMapFragment newInstance() {
        return new GoogleMapFragment();
    }

    public static GoogleMapFragment newInstance(GoogleMapOptions options) {
        Bundle arguments = new Bundle();
        arguments.putParcelable(SUPPORT_MAP_BUNDLE_KEY, options);

        GoogleMapFragment fragment = new GoogleMapFragment();
        fragment.setArguments(arguments);
        return fragment;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mCallback = (OnGoogleMapFragmentListener) getActivity();
        } catch (ClassCastException e) {
            throw new ClassCastException(getActivity().getClass().getName() + " must implement OnGoogleMapFragmentListener");
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = super.onCreateView(inflater, container, savedInstanceState);
        if (mCallback != null) {
            mCallback.onMapReady(getMap());
        }
        return view;
    }

    private OnGoogleMapFragmentListener mCallback;
}

使用模式如下:

public class MyMapActivity implements OnGoogleMapFragmentListener {

    ...

    @Override
    public void onMapReady(GoogleMap map) {
        mUIGoogleMap = map;

        ...

    }

    ...

    private GoogleMap mUIGoogleMap;
}