tabs are not swipping in android

My app crashes when i try to use the set Current Item(arg0.get Position()) in on Tab selected method while implement a the functionality that i click on tabs the fragments below should also change with it..... it works the other way around that is when i swipe, Tabs changes with it. Any kind of help will be appreciable.. thanks in advance. the code is given below:

@TargetApi(Build.VERSION_CODES.HONEYCOMB)

public class AboutUs extends FragmentActivity implements TabListener {

private ActionBar actionBar;
ViewPager viewPager;

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.aboutus);
    intialization();

}

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private void intialization() {
    // TODO Auto-generated method stub

    actionBar = getActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    ActionBar.Tab tab1 = actionBar.newTab();
    tab1.setText("MUMTAZ ANWAR");
    tab1.setTabListener(this);

    ActionBar.Tab tab2 = actionBar.newTab();
    tab2.setText("CREDIENTIALS");
    tab2.setTabListener(this);

    actionBar.addTab(tab1);
    actionBar.addTab(tab2);

    viewPager = (ViewPager) findViewById(R.id.pagger);
    viewPager.setAdapter(new MyAdapter(getSupportFragmentManager()));
    viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

        @Override
        public void onPageSelected(int arg0) {
            // TODO Auto-generated method stub
            actionBar.setSelectedNavigationItem(arg0);
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onPageScrollStateChanged(int arg0) {
            // TODO Auto-generated method stub

        }
    });

}

@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
    // TODO Auto-generated method stub
    //Log.d("HAMZA", "onTabReselected at  " + "position" + tab.getPosition()
    //      + "name" + tab.getText());
}

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
    // TODO Auto-generated method stub
    //Log.d("HAMZA", "onTabselected at  " + "position" + tab.getPosition()
        //  + "name" + tab.getText());
    viewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
    // TODO Auto-generated method stub
    //Log.d("HAMZA", "onTabUnselected at  " + "position" + tab.getPosition()
    //      + "name" + tab.getText());
}

}

class MyAdapter extends FragmentPagerAdapter {

public MyAdapter(FragmentManager fm) {
    super(fm);
    // TODO Auto-generated constructor stub
}

@Override
public Fragment getItem(int arg0) {
    // TODO Auto-generated method stub

    Fragment fragment = null;
    if (arg0 == 0) {

        fragment = new BlankFragment();
    }

    if (arg0 == 1) {

        fragment = new BlankFragmenta();
    }

    return fragment;
}

@Override
public int getCount() {
    // TODO Auto-generated method stub
    return 2;
}

}