public class MainActivity extends ActionBarActivity {

    final static private String APP_KEY = "key_here";
    final static private String APP_SECRET = "secret_here";
    final static private AccessType ACCESS_TYPE = AccessType.DROPBOX;
    private static final boolean USE_OAUTH1 = false;

    // You don't need to change these, leave them alone.
    final static private String ACCOUNT_PREFS_NAME = "prefs";
    final static private String ACCESS_KEY_NAME = "ACCESS_KEY";
    final static private String ACCESS_SECRET_NAME = "ACCESS_SECRET";


    // In the class declaration section;
    protected DropboxAPI<AndroidAuthSession> mDBApi;
    static String[] fnames;


    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        // Notice that setContentView() is not used, because we use the root
        // android.R.id.content as the container for each fragment


        // setup action bar for tabs
        ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        actionBar.setDisplayShowTitleEnabled(true);

        final String info = "Info";
        final String db = "Dropbox";
        Tab tab = actionBar.newTab()
                           .setText(info)
                           .setTabListener(new TabListener<InfoFragment>(
                                   this,"info", InfoFragment.class));
        actionBar.addTab(tab);

        tab = actionBar.newTab()
                       .setText(db)
                       .setTabListener(new TabListener<DbFragment>(
                               this, "dropbox", DbFragment.class));
        actionBar.addTab(tab);

     // And later in some initialization function:
        AndroidAuthSession session = buildSession();
        mDBApi = new DropboxAPI<AndroidAuthSession>(session);


        if (USE_OAUTH1){
            mDBApi.getSession().startAuthentication(MainActivity.this);
        } else{
            mDBApi.getSession().startOAuth2Authentication(MainActivity.this);
        }

        int i = 0;
        fnames = null;
        Entry entries;
        ArrayList<Entry> files = new ArrayList<Entry>();
        ArrayList<String> dir = new ArrayList<String>();
        try {
            entries = mDBApi.metadata("/", 100, null, true, null);
            for (Entry e: entries.contents){
                if (!e.isDeleted){
                    files.add(e);
                    dir.add(new String(files.get(i++).path));
                }
            }
        } catch (DropboxException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        fnames = dir.toArray(new String[dir.size()]);
    }





    public static class TabListener<T extends Fragment> implements ActionBar.TabListener {
        private Fragment mFragment;
        private final Activity mActivity;
        private final String mTag;
        private final Class<T> mClass;

        /** Constructor used each time a new tab is created.
          * @param activity  The host Activity, used to instantiate the fragment
          * @param tag  The identifier tag for the fragment
          * @param clz  The fragment's Class, used to instantiate the fragment
          */
        public TabListener(Activity activity, String tag, Class<T> clz) {
            mActivity = activity;
            mTag = tag;
            mClass = clz;
        }

        /* The following are each of the ActionBar.TabListener callbacks */

        public void onTabSelected(Tab tab, FragmentTransaction ft) {
            // Check if the fragment is already initialized
            if (mFragment == null) {
                // If not, instantiate and add it to the activity
                mFragment = Fragment.instantiate(mActivity, mClass.getName());
                ft.add(android.R.id.content, mFragment, mTag);
            } else {
                // If it exists, simply attach it in order to show it
                ft.attach(mFragment);
            }
        }

        public void onTabUnselected(Tab tab, FragmentTransaction ft) {
            if (mFragment != null) {
                // Detach the fragment, because another one is being attached
                ft.detach(mFragment);
            }
        }

        public void onTabReselected(Tab tab, FragmentTransaction ft) {
            // User selected the already selected tab. Usually do nothing.
        }
    }

    @Override
    public void onResume(){
        super.onResume();
        if (mDBApi.getSession().authenticationSuccessful()){
            try{
                //Required to complete auth, sets the access token on the session
                mDBApi.getSession().finishAuthentication();

                String accessToken = mDBApi.getSession().getOAuth2AccessToken();
            } catch (IllegalStateException e ){
                Log.i("DBAuthLog", "Error authenticating",e );
            }
        }
    }

    private void loadAuth(AndroidAuthSession session) {
        SharedPreferences prefs = getSharedPreferences(ACCOUNT_PREFS_NAME, 0);
        String key = prefs.getString(ACCESS_KEY_NAME, null);
        String secret = prefs.getString(ACCESS_SECRET_NAME, null);
        if (key == null || secret == null || key.length() == 0 || secret.length() == 0) return;

        if (key.equals("oauth2:")) {
            // If the key is set to "oauth2:", then we can assume the token is for OAuth 2.
            session.setOAuth2AccessToken(secret);
        } else {
            // Still support using old OAuth 1 tokens.
            session.setAccessTokenPair(new AccessTokenPair(key, secret));
        }
    }


    /**
     * Shows keeping the access keys returned from Trusted Authenticator in a local
     * store, rather than storing user name & password, and re-authenticating each
     * time (which is not to be done, ever).
     */
    private void storeAuth(AndroidAuthSession session) {
        // Store the OAuth 2 access token, if there is one.
        String oauth2AccessToken = session.getOAuth2AccessToken();
        if (oauth2AccessToken != null) {
            SharedPreferences prefs = getSharedPreferences(ACCOUNT_PREFS_NAME, 0);
            Editor edit = prefs.edit();
            edit.putString(ACCESS_KEY_NAME, "oauth2:");
            edit.putString(ACCESS_SECRET_NAME, oauth2AccessToken);
            edit.commit();
            return;
        }
        // Store the OAuth 1 access token, if there is one.  This is only necessary if
        // you're still using OAuth 1.
        AccessTokenPair oauth1AccessToken = session.getAccessTokenPair();
        if (oauth1AccessToken != null) {
            SharedPreferences prefs = getSharedPreferences(ACCOUNT_PREFS_NAME, 0);
            Editor edit = prefs.edit();
            edit.putString(ACCESS_KEY_NAME, oauth1AccessToken.key);
            edit.putString(ACCESS_SECRET_NAME, oauth1AccessToken.secret);
            edit.commit();
            return;
        }
    }

    private AndroidAuthSession buildSession() {
        AppKeyPair appKeyPair = new AppKeyPair(MainActivity.APP_KEY, MainActivity.APP_SECRET);

        AndroidAuthSession session = new AndroidAuthSession(appKeyPair);
        loadAuth(session);
        return session;
    }

}

public class DbFragment extends ListFragment {

    private ListView mListView;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {


        String[] xfnames = MainActivity.fnames;


        ListView listView = new ListView(getActivity());
        ArrayAdapter<String> array = new ArrayAdapter<String>(getActivity(),
                android.R.layout.simple_list_item_1, xfnames);

        for (String str: xfnames)
            array.add(str);
        setListAdapter(array);



        return super.onCreateView(inflater, container, savedInstanceState);
    }




}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello">
        android:layout_marginTop="40dp"
        android:textSize="40sp"/>
    </TextView>

    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">

    </ListView>


</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">

    </ListView>


</RelativeLayout>