How do I know the map is ready to get used when using the SupportMapFragment?

Question

In the onCreate method, I am making use of the SupportMapFragment to show a map.

    SupportMapFragment fragment = new SupportMapFragment();     getSupportFragmentManager().beginTransaction()             .add(android.R.id.content, fragment).commit(); 

In conjunction to this, I would like to add a marker. The problem is when the call to getMap is null, when can I try again? Is there an event I can register for or is my approach in and of itself wrong?

    mMap = ((SupportMapFragment)(getSupportFragmentManager().findFragmentById(R.id.map))).getMap();     if(mMap == null)         //what do I do here? 

The map is in fact displaying on the phone however I appear to be having no luck in obtaining the reference to add markers.

UPDATE:

The reason I was creating the SupportMapFragment via the constructor is because the typical setContentView was crashing and did not work. This put me in the predicament where I could not obtain my reference in the onCreate method since I was in fact creating the SupportMapFragment at that time. In further investigation, it appears my setContentView issue was a byproduct of not having both the Google-play-services jar AND the module/src set up as part of the overall project. Upon doing BOTH of these, setContentView now works and I can obtain the reference via getMap() as I would expect.

lots.xml...

<?xml version="1.0" encoding="utf-8"?> <fragment xmlns:android="http://schemas.android.com/apk/res/android"           android:id="@+id/map"           android:name="com.google.android.gms.maps.SupportMapFragment"           android:layout_width="match_parent"           android:layout_height="match_parent" /> 

LotsActivity.java...

public class LotsActivity extends FragmentActivity {     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.lots);          GoogleMap mMap;         mMap = ((SupportMapFragment)(getSupportFragmentManager().findFragmentById(R.id.map))).getMap();         if(mMap == null)             //this should not occur now     } 

Answer 1

EDIT: getMap is deprecated now

The problem is when the call to getMap is null, when can I try again?

That depends upon the nature of the problem.

If you set up the SupportMapFragment via the <fragment> element in the layout, you can call getMap() successfully in onCreate(). But, if you create the SupportMapFragment via the constructor, that's too soon -- the GoogleMap does not yet exist. You can extend SupportMapFragment and override onActivityCreated(), as getMap() is ready by then.

However, getMap() can also return null for a bigger problem, such as Google Play Services not being installed. You would need to use something like GooglePlayServicesUtil.isGooglePlayServicesAvailable() to detect this condition and deal with it however you wish.

Answer 2

I ended up extending the SupportMapFragment class and using a callback. The code is here:

public class MySupportMapFragment extends SupportMapFragment {  public MapViewCreatedListener itsMapViewCreatedListener;  // Callback for results  public abstract static class MapViewCreatedListener {     public abstract void onMapCreated(); }  @Override public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {     View view = super.onCreateView(inflater, container, savedInstanceState);     // Notify the view has been created     if( itsMapViewCreatedListener != null ) {         itsMapViewCreatedListener.onMapCreated();     }     return view; } } 

I would rather have used an interface and override the onAttach(activity) method, but in my case, I didn't want the callback to go back to my MainActivity. I wanted it to return to an instance of Fragment. (The GoogleMap was essentially a fragment inside a fragment) I setup the callback and programmatically loaded the map with this. I would like to have set itsMapViewCreatedListener inside the constructor of MySupportMapFragment, but using anything other than parameterless constructors is discouraged.

itsMySupportMapFragment = new MySupportMapFragment(); MapViewCreatedListener mapViewCreatedListener = new MapViewCreatedListener() {     @Override     public void onMapCreated() {         initPlacesGoogleMapCtrl();     } }; itsMySupportMapFragment.itsMapViewCreatedListener = mapViewCreatedListener; FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.mapFragmentContainer, itsMySupportMapFragment); transaction.addToBackStack(null); transaction.commit(); 

And then, when I got the call back, I could get the map; no more null!

public void initPlacesGoogleMapCtrl() {     // Map ready, get it.     GoogleMap googleMap = itsMySupportMapFragment.getMap();     // Do what you want... }