ListFragment setRetainInstance (true); does not work

Question

I use ListFragment

setRetainInstance (true); does not work, I do not know why

savedInstanceState == null

my sources

  public class Fragment_Left extends ListFragment {

        @Override
        public void onAttach(Activity activity) {
            super.onAttach(activity);
            Log.d(LOG_TAG, "Fragment1 onAttach");
        }

        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            Log.d(LOG_TAG, "Fragment1 onCreate");
        }

        @Override
        public void onActivityCreated(Bundle savedInstanceState) {
            super.onActivityCreated(savedInstanceState);

            setRetainInstance(true);

        }

        @Override
        public void onListItemClick(ListView l, View v, int position, long id) {
            getListAdapter().getItem(position);

        }



         public void onSaveInstanceState(Bundle state) {
                super.onSaveInstanceState(state);
                Log.i(LOG_TAG, "onSaveInstanceState()");


            }


}

---

    public class Fragment_Left extends ListFragment {
        private ArrayList<Menu_item> menu_list;  .....

     @Override
        public void onActivityCreated(Bundle savedInstanceState) {
            super.onActivityCreated(savedInstanceState);

            setRetainInstance(true);   
menu_list = new ArrayList<Menu_item>();......

but After I turned Screen menu_list is null, or I did something wrong?

Answer 1

how do I store an array in a fragment?

I am assuming that by "store an array in a fragment" that you mean "retain an array used by a fragment across configuration changes". If so:

Option #1: Put it in a data member of the fragment, and call setRetainInstance(true) on that fragment.

Option #2: If the array is of a data type that is supported by Bundle, override onSaveInstanceState(), put the data in the Bundle, and retrieve that data in other methods in the new fragment instance created after the configuration change (e.g., onCreateView()).

Option #3: If the array really represents the data model of your app, hold it in a central persistent spot that the old and new fragment instances can access, such as a database or a file.