CODEWITHSUNDEEP
androidnullpointerexception
ANGEL0
ANGEL0

Reputation: 13

Fragment Nullpointer Exception on Interface Callback

I'm trying to make my first Android app and I'm stuck with the following problem:

I implemented an interface in my host activity, which I have created. The problem is that I get a NullPointerException when I call the method in my fragment.

Interface

public interface GameInterface {
    public void gameOver();
}

Fragment

public class GameFragment extends Fragment implements View.OnClickListener {
...
    GameInterface gameInterface;

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

        Button trueButton = (Button) getView().findViewById(R.id.button_true);
        trueButton.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        ...
        gameInterface.gameOver();
    }
}

Activity

public class MainActivity extends Activity implements GameInterface {
...
    private void showStartFragment() {
        StartFragment startFragment = new StartFragment();
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.replace(R.id.container, startFragment);
        ft.commit();
    }  

    @Override
    public void gameOver() {
        showStartFragment();
    }
}

I get the NullPointerException in the fragment on the line where I call gameInterface.gameOver();.

Upvotes: 1

Views: 1246

Answers (1)

mbmc
mbmc

Reputation: 5105

The variable was not initialized. Add that in onActivityCreated

gameInterface = (GameInterface) getActivity();

Assuming GameFragment is created in MainActivity

Edit (thanks @Squonk):

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    gameInterface = (GameInterface) activity
}

Upvotes: 2

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