Update data in ListFragment as part of ViewPager

Barkside's answer works with FragmentPagerAdapter but doesn't work with FragmentStatePagerAdapter, because it doesn't set tags on fragments it passes to FragmentManager.

With FragmentStatePagerAdapter it seems we can get by, using its instantiateItem(ViewGroup container, int position) call. It returns reference to fragment at position position. If FragmentStatePagerAdapter already holds reference to fragment in question, instantiateItem just returns reference to that fragment, and doesn't call getItem() to instantiate it again.

So, suppose, I'm currently looking at fragment #50, and want to access fragment #49. Since they are close, there's a good chance the #49 will be already instantiated. So,

ViewPager pager = findViewById(R.id.viewpager);
FragmentStatePagerAdapter a = (FragmentStatePagerAdapter) pager.getAdapter();
MyFragment f49 = (MyFragment) a.instantiateItem(pager, 49)

OK, I think I've found a way to perform request b) in my own question so I'll share for others' benefit. The tag of fragments inside a ViewPager is in the form "android:switcher:VIEWPAGER_ID:INDEX", where VIEWPAGER_ID is the R.id.viewpager in XML layout, and INDEX is the position in the viewpager. So if the position is known (eg 0), I can perform in updateFragments():

      HomeListFragment fragment = 
          (HomeListFragment) getSupportFragmentManager().findFragmentByTag(
                       "android:switcher:"+R.id.viewpager+":0");
      if(fragment != null)  // could be null if not instantiated yet
      {
         if(fragment.getView() != null) 
         {
            // no need to call if fragment's onDestroyView() 
            //has since been called.
            fragment.updateDisplay(); // do what updates are required
         }
      }

I've no idea if this is a valid way of doing it, but it'll do until something better is suggested.