getSupportFragmentManager().findFragmentById returns null for google maps in fragment in android?

Question

I have a problem with Google Maps, i.e. getSupportFragmentManager().findFragmentById returns always null. Do you have an idea how to solve this?

Here is the code:

fragment_map.xml:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.myapp.something.MapFragment">
<fragment
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    class="com.google.android.gms.maps.SupportMapFragment" />                  
</FrameLayout>

MapsFragment.java:

public class MapFragment extends Fragment implements OnMapReadyCallback, android.location.LocationListener

public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    SupportMapFragment mapFragment = (SupportMapFragment) this.getActivity().getSupportFragmentManager().findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);
...

I have Google Maps in Activity and it works with code:

SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);

I am trying to reuse this in fragment, becouse I need maps in fragment, not in activity, but it doesn't work.

I tried:

• calling this code in "onCreateView" function
• SupportMapFragment mapFragment = (SupportMapFragment) getFragmentManager().findFragmentById(R.id.map);
• GoogleMap mGoogleMap = ((SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map)).getMap(); is deprecated, and application crashes
• SupportMapFragment mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map); and similar variations, but in all cases I get null for mapFragment.

Do you know how could I solve this problem?

Solution

The problem is that you're trying to use the Activity's FragmentManager, and you should be using the Fragment's child FragmentManager.

Remove the onCreate() override in the Fragment, and add an onCreateView() Override where you inflate the layout and call getMapAsync():

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.fragment_map, container, false);

    SupportMapFragment mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map);

    mapFragment.getMapAsync(this);

    return rootView;
}

Comments

[Vladimir88dev]

Tnx for the reply, but this code also dosen't work. findFragmentById still returns null.

[Vladimir88dev]

Done. Tnx again :)

[Daniel Nugent]

@Aboulfotoh Your specific issue is probably different than the OP's issue here. How exactly does it not work for you?

[Aboulfotoh]

@DanielNugent it give me a null reference object

[Daniel Nugent]

@Aboulfotoh Does your layout xml look like fragment_map.xml in the question?

[Aboulfotoh]

@DanielNugent Yes, exactly the same

[Daniel Nugent]

@Aboulfotoh What exactly is null for you?

[Aboulfotoh]

@DanielNugent it worked fine now, I was using ButterKnife and it cuases the problem

[Fiphe]

I had the same problem. It took me a lot of time before seeing you answer. Thanks to you it worked. Thanks.

[deadfish]

But why? Why I should use getChildFragmentManager()?

[Daniel Nugent]

@deadfish It's just how they set up the framework. If you use a SupportMapFragment inside an activity, you can just use the activity fragment manager. If you use a SupportMapFragment inside of a fragment, you then have nested fragments, and you need to use the outer fragment's child fragment manager in order for it to work.