hyunikel hyunikel - 2 months ago 10
Android Question

NullPointerException : FragmentManager.beginTransaction()

I'm getting this error while trying to launch a Fragment from a first Fragment :

java.lang.NullPointerException: Attempt to invoke virtual method 'android.app.FragmentTransaction android.app.FragmentManager.beginTransaction()' on a null object reference


Here's the method where I'm getting the error :

@Override
public void onClick(View v) {
Fragment fragment = new PropertyFragment();
if (fragment != null) {
FragmentManager fragmentManager = fragment.getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack so the user can navigate back
fragmentTransaction.replace(R.id.rent_viewer, fragment);
fragmentTransaction.addToBackStack(null);

// Commit the transaction
fragmentTransaction.commit();
}
}


Precisely, the following code instruction is causing the error :

fragmentManager.beginTransaction();


Here's how the class and the nested class look like :

public class RentFragment extends Fragment {

...

@SuppressWarnings("unused")
private OnRentFragmentInteractionListener mListener;

public RentFragment() {
}

@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mListener = (OnRentFragmentInteractionListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnRentFragmentInteractionListener");
}
}

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

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_rent, container, false);

myOnClickListener = new RentOnClickListener(getActivity());

return rootView;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
}

@Override
public void onDetach() {
super.onDetach();
mListener = null;
}

public interface OnRentFragmentInteractionListener {
public void onRentFragmentInteraction(Uri uri);
}

private static class RentOnClickListener implements View.OnClickListener {

private final Context context;

private RentOnClickListener(Context context) {
this.context = context;
}

@Override
public void onClick(View v) {
Fragment fragment = new PropertyFragment();
if (fragment != null) {
FragmentManager fragmentManager = fragment.getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack so the user can navigate back
fragmentTransaction.replace(R.id.rent_viewer, fragment);
fragmentTransaction.addToBackStack(null);

// Commit the transaction
fragmentTransaction.commit();
}
}
}
}

Answer

FragmentManager will be null until it is attached to the activity.So use below code , If it is a nested Fragment use this.getChildFragmentManager() for your fragment class else use getActivity().getFragmentManager() or getActivity().getSupportFragmentManager().