Awesome! So, finally, now that we are using 2 fragment types we need to remember to set and retrieve our fragments using

   public class MainActivity extends AppCompatActivity implements NewsFragment.NewsListener {
    // New tags for referring to fragments
    public static final String NEWS_FRAGMENT = "news_fragment";
    public static final String NEWSITEM_FRAGMENT = "newsitem_fragment";

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

        FragmentManager fragmentManager = getFragmentManager();


NewsFragment savedFragment = (NewsFragment) fragmentManager.findFragmentByTag(NEWS_FRAGMENT);


 fragmentTransaction.replace(R.id.placeholder, fragment, NEWSITEM_FRAGMENT);



        if (savedFragment == null) {
            NewsFragment newsFragment = new NewsFragment();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.add(R.id.placeholder, newsFragment,"NEWS_FRAGMENT");
            fragmentTransaction.commit();

          //getFragmentManager().beginTransaction().replace(R.id.MainFrameLayout,fragmentA,"YOUR_TARGET_FRAGMENT_TAG").addToBackStack("YOUR_SOURCE_FRAGMENT_TAG").commit(); 

        }

    }

    @Override
    public void onNewsItemSelected(int index) {
        NewsItemFragment fragment = new NewsItemFragment();
        // TODO: how do we pass arguments to the new Fragment?
        FragmentManager fragmentManager = getFragmentManager();
            Bundle bundle = new Bundle();
             FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
                bundle.putInt(NewsItemFragment.KEY_NEWS_ITEM_INDEX,0); 
               fragment.setArguments(bundle);

        fragmentTransaction.replace(R.id.placeholder, fragment, "NEWSITEM_FRAGMENT");
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commit();
    }
}

public class NewsItemFragment extends Fragment {
    public static final String KEY_NEWS_ITEM_INDEX = "news_item_index";

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // TODO:  Hmmm, how do we get this index?
        int index = getArguments().getInt(NewsItemFragment.KEY_NEWS_ITEM_INDEX);
        getActivity().setTitle(News.headlines[index]);
        View view = inflater.inflate(R.layout.fragment_newsitem, container, false);
        return view;
    }




    @Override
    public void onStop() {
        super.onStop();
        getActivity().setTitle(getResources().getString(R.string.app_name));
    }
}

public class News {
    public static String[] headlines = new String[]{
      "Treehouse student develops #1 App in Google App Store",
      "Oracle and Google decide to hug it out",
      "Java8 coming to Android!  Is it too late?"
    };
}