Android : How do I make Tabwidget inside fragment

Sorry for my poor English skill.

My prog make navigation drawer for 3 fragment. I want to make fragment_1 with tab widget + 3 tab sub fragment.

This is my MainActivity

public class MainActivity extends FragmentActivity implements NavigationDrawerFragment.NavigationDrawerCallbacks {

private NavigationDrawerFragment mNavigationDrawerFragment;
private CharSequence mTitle;

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

    mNavigationDrawerFragment = (NavigationDrawerFragment) getFragmentManager()
            .findFragmentById(R.id.navigation_drawer);
    mTitle = getTitle();

    // Set up the drawer.
    mNavigationDrawerFragment.setUp(R.id.navigation_drawer,
            (DrawerLayout) findViewById(R.id.drawer_layout));
}

and Activity_main

<android.support.v4.widget.DrawerLayout    xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.seoulin.MainActivity" >

    <FrameLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <fragment
        android:id="@+id/navigation_drawer"
        android:name="com.example.seoulin.NavigationDrawerFragment"
        android:layout_width="@dimen/navigation_drawer_width"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        tools:layout="@layout/fragment_navigation_drawer" />
</android.support.v4.widget.DrawerLayout>

I want to make tab inside homefragment(fragment_1) this is fragment_1 but it's not working :(. plz help or give advise for me. Thanks.

public class Fragment_Tab_1 extends Fragment{

private FragmentTabHost mTabHost;

//Mandatory Constructor
public Fragment_Tab_1() {
}

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

}

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.fragment_tab_1,container, false);

    mTabHost = (FragmentTabHost)rootView.findViewById(android.R.id.tabhost);
    mTabHost.setup(getActivity(), getChildFragmentManager(), R.id.realtabcontent);

    mTabHost.addTab(mTabHost.newTabSpec("fragmenta").setIndicator("Fragment A"), FragmentA.class, null);
    mTabHost.addTab(mTabHost.newTabSpec("fragmentb").setIndicator("Fragment B"), FragmentB.class, null);
    mTabHost.addTab(mTabHost.newTabSpec("fragmentc").setIndicator("Fragment C"), FragmentC.class, null);

    return rootView;
    }
}