Salve, ho un problema con la visualizzazione di dati da Database in tabbed Activity.

Se visualizzo i dati in una Activity funziona tutto.
Se invece devo visualizzare i dati in una tab non visualizza nulla.

UserActivity.java
codice:
public class UserActivity extends AppCompatActivity {    TextView nome_view = null;
    TextView email_view = null;




    private final int ON_ACT_RESULT_CAMERA = 1;
    private final int ON_ACT_RESULT_GALLERY = 2;
    private String captured_image_path;
    int selected    =   0;


    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link FragmentPagerAdapter} derivative, which will keep every
     * loaded fragment in memory. If this becomes too memory intensive, it
     * may be best to switch to a
     * {@link android.support.v4.app.FragmentStatePagerAdapter}.
     */
    private SectionsPagerAdapter mSectionsPagerAdapter;


    /**
     * The {@link ViewPager} that will host the section contents.
     */
    private ViewPager mViewPager;


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


        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());


        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);


        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);
........................................................................
le 3 tab hanno questo codice (rispettivamente 1 / 2 / 3)
codice:
public class Dati1Fragment extends Fragment {



    public Dati1Fragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_dati1, container, false);
    }
}
c'è differenza di metodo tra una Activity (con extends AppCompatActivity) e una con extends fragment?

Chi mi può dare delucidazioni?
Grazie