使用 Maps API v2 以编程方式初始化 MapFragment [英] Initialize MapFragment programmatically with Maps API v2

问题描述

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

I'm trying to add a MapFragment to my current Fragment. The use of nested fragments is restricted to FragmentTransactions, you can't use the xml tag in your layout. Also, I want it to be added to the main Fragment when the user presses a button. So, I'm creating the MapFragment programmatically with getInstance() when the user presses that button and adding it to the proper place. It is shown correctly, so far so good.

问题是在附加 MapFragment 后，我​​需要获得对 GoogleMap 的引用以放置标记，但是 getMap()方法返回 null(因为片段的 onCreateView() 还没有被调用).

The problem is that after attaching the MapFragment I need to get a reference to GoogleMap to place a Marker, but the getMap() method returns null (as the fragment's onCreateView() hasn't been called yet).

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

I looked at the demo example code and I found the solution they use is initializing the MapFragment in onCreate() and getting the reference to GoogleMap in onResume(), after onCreateView() has been called.

我需要在 MapFragment 初始化后立即获取对 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地图并设置它的可见性消失，但我希望地图默认关闭，因此如果他们没有明确要求，它不会占用用户的带宽为它.

I need to get the reference to GoogleMap right after the MapFragment initialization, because I want the users to be able to show or hide the map with a button. I know a possible solution would be to create the Map at the start as said above and just set it's visibility gone, but I want the map to be off by default so it doesn't take the user's bandwidth if they don't explicitly asked for it.

我尝试使用 MapsInitializer，但也不起作用.我有点卡住了.有任何想法吗?到目前为止，这是我的测试代码:

I tried with the MapsInitializer, but doesn't work either. I'm kind of stuck. Any ideas? Here is my testing code so far:

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

推荐答案

好的 AnderWebs 在 Google+ 但他太懒了.... 忙着写在这里，所以这里是简短的版本:扩展 MapFragment 类并覆盖 onCreateView() 方法.完成此方法后，我们可以获得对 GoogleMap 对象的非空引用.

The good AnderWebs gave me an answer in Google+ but he is too laz.... emm busy to write it here again, so here is the short version: Extend the MapFragment class and override the onCreateView() method. After this method is done we can get a non-null reference to que GoogleMap object.

这是我的特殊解决方案:

This is my particular solution:

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)));
    }
}

现在在之前的 Fragment 类中我做

Now in the previous Fragment class I do

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.但不确定是因为这个还是别的什么问题.

Maybe it's not perfect yet, because the screen blinks when showing the map. But not sure if the problem is because of this or something else.

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