Fragment update view in view pager

Question

I am using view pager which is having 3 fragments

public class ViewPagerAdapter extends FragmentStatePagerAdapter {

    private static final String TAG="ViewPageAdapter";
    private final int PAGES = 3;
    private String[] title = new String[]{"Frag1",
            "Frag2", "Frag2"};

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

    @Override
    public Fragment getItem(int position) {
        Log.d(TAG, "position is " + position);
        switch (position) {
            case 0:
                return new Frag1();
            case 1:
                return new Frag2();
            case 2:
                return new Frag3();
            default:
                throw new IllegalArgumentException(
                        "The item position should be less or equal to:" + PAGES);
        }
    }

    @Override
    public int getCount() {
        return PAGES;
    }

    @Override
    public int getItemPosition(Object object) {
        return POSITION_NONE;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return title[position];
    }

}

I am setting view pager from main activity:

viewPageAdapter = new ViewPagerAdapter(getSupportFragmentManager());
viewPager.addOnPageChangeListener(onPageChangeListener);
viewPager.setAdapter(viewPageAdapter);

When i execute viewPageAdapter.notifyDataSetChanged(); or viewPager.setAdapter(viewPageAdapter); method to recreate fragments the activity is getting destroyed.don't know what causing the issue. I checked many solution nothing worked. ViewPager PagerAdapter not updating the View

Update ViewPager dynamically?

I am asking another problem because which is related to above question. The problem which is described in link ViewPager onPageSelected for first page where i am not able to get first page tab title on load.i am using android.support.v4.view.PagerTabStrip

Please help me in getting solved. Wasted my whole day to get rid of this :(