Handle Fragment duplication on Screen Rotate (with sample code)

Question

There are some similar answers, but not to this situation.

---

My situation is simple.

I have an Activity with two different layouts, one in Portrait,

Answer 1

@midnite ,first of all thanks for your question, I had the same question, on wich I worked for days. Now I wound some tricky resolution to this problem - and want to share this to community. But If someone has better solution, please write in comments.

So, I have same situation - different layouts for two device orientation. In portrait there is no need for DetailsFragment.

I simply in OnCreate trying to find already created fragments:

    fragment = (ToDoListFragment) getFragmentManager().findFragmentByTag(LISTFRAGMENT);
    frameDetailsFragment = (FrameLayout) findViewById(R.id.detailsFragment);
    detailsFragment = (DetailsFragment) getFragmentManager().findFragmentByTag(DETAILS_FRAGMENT);
    settingsFragment = (SettingsFragment) getFragmentManager().findFragmentByTag(SETTINGS_FRAGMENT);

Right after that I am adding my main fragment -

    if (fragment == null){
        fragment = new ToDoListFragment();
        getFragmentManager().beginTransaction()
                .add(R.id.container, fragment, LISTFRAGMENT)
                .commit();
    }

And clear back stask of my fragments:

  if (getFragmentManager().getBackStackEntryCount() > 0 ) {
        getFragmentManager().popBackStackImmediate();
    }

And the MOST interesting is here -

  destroyTmpFragments();

Here is the method itself:

  private void destroyTmpFragments(){
    if (detailsFragment != null && !detailsFragment.isVisible()) {
        Log.d("ANT", "detailsFragment != null, Destroying");
        getFragmentManager().beginTransaction()
                .remove(detailsFragment)
                .commit();

        detailsFragment = null;
    }

    if (settingsFragment != null && !settingsFragment.isVisible()) {
        Log.d("ANT", "settingsFragment != null, Destroying");
        getFragmentManager().beginTransaction()
                .remove(settingsFragment)
                .commit();

        settingsFragment = null;
    }
}

As you can see, I clean manually all fragments, that FragmentManager gentfully saved for me (great thanks to him). In log I have next lifecycle calls:

 04-24 23:03:27.164 3204    3204    D   ANT MainActivity onCreate()
 04-24 23:03:27.184 3204    3204    I   ANT DetailsFragment :: onCreateView
 04-24 23:03:27.204 3204    3204    I   ANT DetailsFragment :: onActivityCreated
 04-24 23:03:27.204 3204    3204    I   ANT DetailsFragment :: onDestroy
 04-24 23:03:27.208 3204    3204    I   ANT DetailsFragment :: onDetach

So in onActivityCreated make your views check for null - in case fragment is not visible. It will be deleted little bit later (It is so maybe cuz fragment manager's remove is async) After, in activity's code we can create brand new Fragment instance, with proper layout (fargmnet's placeholder) and fragment will be able to find it's views for example, and will not produce NullPointerException

But, fragments that are in back stack are deleted pretty fast, without call to onActivityCreated (with th help of above code:

 if (getFragmentManager().getBackStackEntryCount() > 0 ) {
        getFragmentManager().popBackStackImmediate();
    }

At last, at the end i add fragment if I am in land orientation -

 if (frameDetailsFragment != null){
        Log.i("ANT", "frameDetailsFragment != null");

        if (EntryPool.getPool().getEntries().size() > 0) {
            if (detailsFragment == null) {
                detailsFragment = DetailsFragment.newInstance(EntryPool.getPool().getEntries().get(0), 0);
            }

            getFragmentManager().beginTransaction()
                    .replace(R.id.detailsFragment, detailsFragment, DETAILS_FRAGMENT)
                    .commit();
        }
    }