java.lang.IllegalStateException: Content view not yet created

public static MenuItem mSendMenuItem;
public PlaceholderFragment placeholderFragment;

public RecipientsActivity() {
    placeholderFragment = new PlaceholderFragment();
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_recipients);
    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment())
                .commit();
    }

}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch(item.getItemId()) {
        case R.id.action_send:
            ParseObject message = placeholderFragment.createMessage();
            // send(message);
            return true;
    }
    return super.onOptionsItemSelected(item);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_recipients, menu);
    mSendMenuItem = menu.getItem(0);
    return true;
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends ListFragment {

    public final String TAG = PlaceholderFragment.class.getSimpleName();

    public List<ParseUser> mFriends;
    public ParseRelation<ParseUser> mFriendsRelation;
    public ParseUser mCurrentUser;

    private ListView mListView;

    public PlaceholderFragment() {
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);

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

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

    }

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

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

        ParseQuery<ParseUser> query = mFriendsRelation.getQuery();
        query.addAscendingOrder(ParseConstants.KEY_USERNAME);
        mFriendsRelation.getQuery().findInBackground( new FindCallback<ParseUser>() {
            @Override
            public void done(List<ParseUser> parseUsers, ParseException e) {

                if (e == null) {
                    mFriends = parseUsers;
                    String[] usernames = new String[mFriends.size()];
                    int i = 0;
                    for (ParseUser user : mFriends) {
                        usernames[i] = user.getUsername();
                        i++;

                    }
                    ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                            getListView().getContext(),
                            android.R.layout.simple_list_item_checked,
                            usernames);
                    getListView().setAdapter(adapter);
                    getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
                } else {
                    Log.e(TAG, e.getMessage());
                    AlertDialog.Builder builder = new AlertDialog.Builder(getListView().getContext());
                    builder.setMessage(e.getMessage())
                            .setTitle(R.string.error_title)
                            .setPositiveButton(android.R.string.ok, null);
                    AlertDialog dialog = builder.create();
                    dialog.show();
                }
            }
        });
    }
    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);
        if (l.getCheckedItemCount() >0) {
            mSendMenuItem.setVisible(true);
        } else {
            mSendMenuItem.setVisible(false);
        }

    }

    public ParseObject createMessage() {
        ParseObject message = new ParseObject(ParseConstants.CLASS_MESSAGES);
        message.put(ParseConstants.KEY_SENDER_ID, ParseUser.getCurrentUser().getObjectId());
        message.put(ParseConstants.KEY_SENDER_NAME, ParseUser.getCurrentUser().getUsername());
        message.put(ParseConstants.KEY_RECIPIENT_IDS, getRecipientsIds());
        return message;
    }

    protected ArrayList<String> getRecipientsIds() {
        ArrayList<String> recipientsIds = new ArrayList<String>();
        for (int i = 0; i< getListView().getCount(); i++) {
            if(getListView().isItemChecked(i)) {
                recipientsIds.add(mFriends.get(i).getObjectId());
            }
        }
        return recipientsIds;
    }

}