Why don't Checkmarks stay on when the Edit Friends List is opened from Options Menu?

public static final String TAG = EditFriendsActivity.class.getSimpleName();

protected List<ParseUser> mUsers;
protected ParseRelation<ParseUser> mFriendsRelation;
protected ParseUser mCurrentUser;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
    setContentView(R.layout.activity_edit_friends);

    getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.edit_friends, menu);
    return true;
}

@Override
protected void onResume() {
    super.onResume();

    mCurrentUser = ParseUser.getCurrentUser();
    mFriendsRelation = mCurrentUser.getRelation(ParseConstants.KEY_FRIENDS_RELATION);

    setProgressBarIndeterminateVisibility(true);

    ParseQuery<ParseUser> query = ParseUser.getQuery();
    query.orderByAscending(ParseConstants.KEY_USERNAME);
    query.setLimit(1000);
    query.findInBackground(new FindCallback<ParseUser>() {  
        @Override
        public void done(List<ParseUser> users, ParseException e) {
            setProgressBarIndeterminateVisibility(false);

            if (e == null) {
                // Success
                mUsers = users;
                String[] usernames = new String[mUsers.size()];
                int i = 0;
                for(ParseUser user : mUsers) {
                    usernames[i] = user.getUsername();
                    i++;
                }
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                        EditFriendsActivity.this,
                        android.R.layout.simple_list_item_checked,
                        usernames);
                setListAdapter(adapter);

                addFriendCheckmarks();
            }
            else {
                Log.e(TAG, e.getMessage());
                AlertDialog.Builder builder = new AlertDialog.Builder(EditFriendsActivity.this);
                builder.setMessage(e.getMessage())
                    .setTitle(R.string.error_title)
                    .setPositiveButton(android.R.string.ok, null);
                AlertDialog dialog = builder.create();
                dialog.show();
            }
        }
    });
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);

    if (getListView().isItemChecked(position)) {
        // remove the friend

    }
    else {
        // add the friend
        mFriendsRelation.add(mUsers.get(position));
        mCurrentUser.saveInBackground(new SaveCallback() {

            @Override
            public void done(ParseException e) {
                if (e != null) {
                    Log.e(TAG, e.getMessage());
                }
            }
        });
    }

}

private void addFriendCheckmarks() {
    mFriendsRelation.getQuery().findInBackground(new FindCallback<ParseUser>() {
        @Override
        public void done(List<ParseUser> friends, ParseException e) {
            if (e == null) {
                //list returned - look for a match
                for (int i = 0; i < mUsers.size(); i++) {
                    ParseUser user = mUsers.get(i);

                    for (ParseUser friend : friends) {
                        if (friend.getObjectId().equals(user.getObjectId())) {
                            getListView().setItemChecked(i, true);
                        }
                    }
                }
            }
            else {
                Log.e(TAG, e.getMessage());
            }
        }
    });
}