You’re layering your Fragments one on top of the other.
When a config change occurs the old Fragment adds itself to the new Activity when it’s recreated. This is a massive pain in the rear most of the time.
You can stop errors occurring by using the same Fragment rather than recreating a new one. Simply add this code:
if (savedInstanceState == null) {
// only create fragment if activity is started for the first time
mFragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
FragmentOne fragment = new FragmentOne();
fragmentTransaction.add(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else {
// do nothing - fragment is recreated automatically
}
Be warned though: problems will occur if you try and access Activity Views from inside the Fragment as the lifecycles will subtly change. (Getting Views from a parent Activity from a Fragment isn’t easy).