Need help with part 2 of Handling Clicks challenge

public class NewsFragment extends Fragment {

   public interface NewsListener {
        void onNewsItemSelected(int index);
    }

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

public class MainActivity extends AppCompatActivity implements NewsFragment.NewsListener {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        NewsFragment fragment = new NewsFragment();
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.placeholder, fragment);
        fragmentTransaction.commit();
    }

}