android map in fragment

Question

I am trying to create a android app that has one activity and multiple fragments. Each fragment will ocupy the entire screen when it is in view and with a replace transaction it should be switched to another fragment.

<FrameLayout
    android:id="@+id/content_frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

This is the container for the fragments. The problem is that a fragment that I want to use is a GoogleMap. This is my code for the map fragment:

public class Map extends Fragment{
private final static String TAG = "MAP Fragment";
public GoogleMap googleMap = null;

@Override
public void onCreate(Bundle savedInstanceState) 
{
        super.onCreate(savedInstanceState);
        setUpMapIfNeeded();
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.map_fragment, null);
    return view;
}

private void setUpMapIfNeeded()
{
    if(googleMap == null)
    {
        googleMap = ((MapFragment) getActivity().getFragmentManager().findFragmentById(R.id.map)).getMap();
        if(googleMap != null)
        {
            GoogleMapOptions options = new GoogleMapOptions();
            options.mapType(GoogleMap.MAP_TYPE_NORMAL)
                .camera(new CameraPosition(new LatLng(25f, 47f), 13f, 0f, 0f));
        }
        else
        {
            Log.d(TAG, "googleMap is null !!!!!!!!!!!!!!!");
        }
    }
}

}

and it's layout:

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/map"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:name="com.google.android.gms.maps.MapFragment"/>

And in the Main activity:

@Override
protected void onCreate(Bundle savedInstanceState) 
{
Map test = new Map();
getSupportFragmentManager().beginTransaction()
            .add(R.id.content_frame, test)
            .commit();
}

I get a null pointer exception at: (I belive it cannot find the R.id.map)

googleMap = ((MapFragment) getActivity().getFragmentManager()
.findFragmentById(R.id.map)).getMap();

If I don't use "getActivity()." it says that it cannot cast from Fragment to MapFragment.

I need "googleMap" for creating markers on the map.

When I make the same application but without fragments (my main activity diplays the map and i don't have other fragments) everithing works fine.

I have found this similar topics: Google Maps API v2 Custom MapFragment + SimpleFragment and error using maps in fragment . But if I extend FragmentActivity or SupportMapFragment I cannot replace the fragment with another using transactions.

Conclusion: I would like that when an action occurs (click or something) I only have to replace the fragmens like this:

FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment_container, newFragment);

What am I doing wrong? Or should I take a different approach to the problem?

(P.S. I am realtively new to android)

Answer 1

The problem is that I was trying to change the map element before it was displayed setUpMapIfNeeded() is called in onCreate() (the view is inflated only in onCreateView()).

If I move the call setUpMapIfNeeded() in onResume() everything works because then the view is inflated and it can use the map and modify it.

This is where I found the answer