UserActivity.java

public class UserActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_user);

        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment())
                    .commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.user, menu);
        return true;
    }
    
    public static class PlaceholderFragment extends Fragment{

        private CardArrayAdapter mCardArrayAdapter;
        private CardListView listView;
        private ArrayList<Card> cards;

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_user_n1, container, false);

            cards = new ArrayList<Card>();
            mCardArrayAdapter = new CardArrayAdapter(getActivity(),cards);
            listView = (CardListView) rootView.findViewById(R.id.userDetailList);
            if (listView != null){ listView.setAdapter(mCardArrayAdapter); }

            return rootView;
        }

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