My list view doesn't update when the user responds to an activity?

Question

I have a main activity with many fragments, one of which contains a list view, with adaptor homeworkListAdapter, this adapter does display any items initial in homeworkItems. My activity opens up another activity (HomeworkAddActivity, which gets a string from the user and puts it in an array homeworkItems, this all works as I have checked each step independently. However when I try to update the list view with this new item (using .notifyDataSetChanged) it doesn't update, I have been trying to fix this for 3-4 hours, please help.

Code

MainActivity

    public static ArrayAdapter<String> homeworkListAdapter;

public static ArrayList<String> homeworkItems; 

  ....

protected void onCreate(Bundle savedInstanceState) {
....
homeworkItems = new ArrayList<String>();

homeworkListAdapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, homeworkItems);
....

 public static class HomeworkListViewFragment extends Fragment {

....

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(
                R.layout.fragment_homework_listview, container, false);

        homeworkListView = (ListView) rootView
                .findViewById(R.id.homework_listview);

        homeworkListView.setAdapter(homeworkListAdapter);

        return rootView;
    }

HomeworkAddActivity

public class HomeworkAddActivity extends ActionBarActivity {

....

public void buttonAddHomework(View v) {
    NavUtils.navigateUpFromSameTask(this);
    EditText editText = (EditText) findViewById(R.id.text_new_homework_name);
    String homeworkItem = (String) editText.getText().toString();
    if (!(TextUtils.isEmpty(homeworkItem))) {
        //MainActivity.homeworkList.addItem(homeworkItem);
        MainActivity.homeworkItems.add(homeworkItem);
        MainActivity.homeworkListAdapter.notifyDataSetChanged();
    }
}
 }

Answer 1

Could you make a check like this:

if (!TextUtils.isEmpty(homeworkItem)) {
Toast.makeText(getBaseContext(),"ADDING AN ITEM!!!",Toast.LENGH_SHORT).show()
    homeworkItems.add(homeworkItem);
    homeworkListAdapter.notifyDataSetChanged();
}

just to be sure it passes the check. if it does (and you'll see the toast) then try

    if (!TextUtils.isEmpty(homeworkItem)) {
        homeworkItems.add(homeworkItem);
homeworkListAdapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, homeworkItems);
homeworkListView.setAdapter(homeworkListAdapter);
    }

UPDATE
and the very last thing I assume your ListView has property android:height set to "wrap_content" - try to change it to "match_parent" :) It updates but you cant see it - try to scroll :)) And if this is it you should to fall back to notifyDatasetChanged()