notifyDataSetChanged（）在ListFragment中不起作用

Question

I have a ListView in a ListFragment that is populated via a database query. It loads all the data just fine when it first populates the list in onCreate() . But when I requery the database, assign the return value to assignmentsCursor , and call notifyDataSetChanged() , it doesn't update adapter.mCursor . If I go into the Debugging mode in Eclipse I can see that assignmentsCursor.mCount has changed, but when I look at adapter.mCursor.mCount , it's the same as before. (Yes, I'm checking after notifyDataSetChanged() has been called.)

The relevant parts of my code:

SimpleCursorAdapter adapter;
Cursor assignmentsCursor;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (savedInstanceState != null) {
        course = savedInstanceState.getShort(Values.ASSIGNMENT_KEY_COURSE);
    }
    setRetainInstance(true);

    // Create and array to specify the fields we want
    String[] from = new String[] { Values.KEY_TITLE, Values.ASSIGNMENT_KEY_COURSE };

    // and an array of the fields we want to bind in the view
    int[] to = new int[] { R.id.assignment_list_title, R.id.assignment_list_course };

    // Need to give assignmentsCursor a value -- null will make it not work
    updateAdapter();

    adapter = new SimpleCursorAdapter(context, R.layout.assignment_list_item, assignmentsCursor, from, to);
    setListAdapter(adapter);
}

public void onResume() {
    super.onResume();
    updateAdapter();
    refresh();
}

/**
 * Updates the content in the adapter.
 */
public void updateAdapter() {
    SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(context);
    boolean showingCompleted = sharedPrefs.getBoolean(Values.ASSIGNMENT_KEY_SHOWING_COMPLETED, false);

    if (course < 0) // Showing assignments from all courses
        if (showingCompleted)
            assignmentsCursor = DbUtils.fetchAllAssignments(context, Values.ASSIGNMENT_LIST_FETCH, null, true);
        else
            assignmentsCursor = DbUtils.fetchIncompleteAssignments(context, Values.ASSIGNMENT_LIST_FETCH, null, true);
    else // Showing assignments from specified course
        if (showingCompleted)
            assignmentsCursor = DbUtils.fetchAllAssignments(context, Values.ASSIGNMENT_LIST_FETCH, course, true);
        else
            assignmentsCursor = DbUtils.fetchIncompleteAssignments(context, Values.ASSIGNMENT_LIST_FETCH, course, true);

}

private void refresh() {
    updateAdapter();
    adapter.notifyDataSetChanged();
}

Help me!! ;)

PS If you need any more details/code, just let me know. I am positive that the database is querying correctly though.

Answer 1

Thanks to Deucalion, I have determined that I incorrectly assumed that the adapter was referencing the assignmentsCursor variable as opposed to creating a copy of the Cursor for itself. What I needed to do was just call adapter.changeCursor(assignmentsCursor) so that it updated its local copy. Thanks again Deucalion!