//////////////////////////////////
// part of activity class
//////////////////////////////////
public class Main extends Activity {

    // singleton object
    private static Main sInstance = null;

    // background service object
    protected static Intent bgService = null;

    // tab fragment
    protected Fragment fragmentEvent;
    protected Fragment fragmentProfile;

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

        // set singleton instance
        sInstance = this;

        /**
         * create fragment objects
         */
        fragmentEvent = new FragmentEvent();
        fragmentProfile = new FragmentProfile();



//////////////////////////////////
// part of FRAGMENT class
//////////////////////////////////
public class FragmentEvent extends Fragment {

    /**
     * VARIABLES
     */

    // singleton
    private static FragmentEvent sInstance;

    // placeholder for current Event
    protected Profile profile = null;

    // container for our profiles
    private ViewGroup mContainerView;

    // our fragment view
    private View mView;

...