refresh fragment UI from fragmentActivity

So obviously adjust for your specific needs, but this is what I use for my Application.

 Fragment frag = getSupportFragmentManager().findFragmentByTag("android:switcher:" + R.id.pager + ":" + mPager.getCurrentItem());
    if(frag!=null&&mPager.getCurrentItem()==0)
        {
           ((Fragment1) frag).changeImageView(1);
        }