i try to do ribbit, in fragment section i dont see value of inbox or friend tabs, how i can reach this data as in lesson

    public class MainActivity extends ActionBarActivity implements ActionBar.TabListener {

    public static final String TAG = MainActivity.class.getSimpleName();


    /**
     * 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}.
     */
    SectionsPagerAdapter mSectionsPagerAdapter;

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

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        ParseUser currentUser = ParseUser.getCurrentUser();
        if(currentUser == null) {

            navigateToLogin();
        }
        else{
            Log.i(TAG, currentUser.getUsername());
        }

        // Set up the action bar.
        final ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // 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.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        // When swiping between different sections, select the corresponding
        // tab. We can also use ActionBar.Tab#select() to do this if we have
        // a reference to the Tab.
        mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                actionBar.setSelectedNavigationItem(position);
            }
        });



        // For each of the sections in the app, add a tab to the action bar.
        for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
            // Create a tab with text corresponding to the page title defined by
            // the adapter. Also specify this Activity object, which implements
            // the TabListener interface, as the callback (listener) for when
            // this tab is selected.
            actionBar.addTab(
                    actionBar.newTab()
                            .setText(mSectionsPagerAdapter.getPageTitle(i))
                            .setTabListener(this));
        }
    }

    private void navigateToLogin() {
        Intent intent = new Intent(this, LoginActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
        startActivity(intent);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_logout) {
            ParseUser.logOut();
            navigateToLogin();

        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
        // When the given tab is selected, switch to the corresponding page in
        // the ViewPager.
        mViewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a PlaceholderFragment (defined as a static inner class below).
            return PlaceholderFragment.newInstance(position + 1);
        }

        @Override
        public int getCount() {
            // Show 3 total pages.
            return 2;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            Locale l = Locale.getDefault();
            switch (position) {
                case 0:
                    return getString(R.string.title_section1).toUpperCase(l);
                case 1:
                    return getString(R.string.title_section2).toUpperCase(l);
            }
            return null;
        }
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        private static final String ARG_SECTION_NUMBER = "section_number";

        /**
         * Returns a new instance of this fragment for the given section
         * number.
         */
        public static PlaceholderFragment newInstance(int sectionNumber) {
            PlaceholderFragment fragment = new PlaceholderFragment();
            Bundle args = new Bundle();
            args.putInt(ARG_SECTION_NUMBER, sectionNumber);
            fragment.setArguments(args);
            return fragment;
        }

        public PlaceholderFragment() {
        }

    }
}

/** * Created by ahmetyuva on 06/04/15. */ public class InboxFragment extends ListFragment { @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_inbox, container, false);

    return rootView;
}

package com.ahmetyuva.ribbit;

/** * Created by ahmetyuva on 06/04/15. */

import android.content.Context; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentManager; import android.support.v4.app.FragmentPagerAdapter;

import java.util.Locale;

/** * A {@link android.support.v4.app.FragmentPagerAdapter} that returns a fragment corresponding to * one of the sections/tabs/pages. */ public class SectionsPagerAdapter extends FragmentPagerAdapter {

protected Context mContext;

public SectionsPagerAdapter(Context context, FragmentManager fm) {
    super(fm);
    mContext = context;
}

@Override
public Fragment getItem(int position) {
    // getItem is called to instantiate the fragment for the given page.
    // Return a PlaceholderFragment (defined as a static inner class below).

    switch (position){
        case 0:
            return new InboxFragment();
        case 1:
            return new FriendsFragment();
    }

    return null;

}

@Override
public int getCount() {

    return 2;
}

@Override
public CharSequence getPageTitle(int position) {
    Locale l = Locale.getDefault();
    switch (position) {
        case 0:
            return mContext.getString(R.string.title_section1).toUpperCase(l);
        case 1:
            return mContext.getString(R.string.title_section2).toUpperCase(l);

    }
    return null;
}

<ListView
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:id="@android:id/list"
    android:layout_centerHorizontal="true"
    android:layout_alignParentTop="true"/>

<TextView
    android:id="@android:id/empty"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="@string/empty_inbox_label"/>