AddView (View) не поддерживается в AdapterView

Я начинаю разработку Android, и я получаю эту ошибку в заголовке.

Вот мои Contacts.java

package us.inevent.toot;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class Contacts extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_contacts);

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new ContactListFragment()).commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.contacts, menu);
        return true;
    }

    @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);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class ContactListFragment extends Fragment {

        private ViewGroup listContacts;

        public ContactListFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState)
        {

            View rootView = inflater.inflate(R.layout.fragment_contacts,
                    container, false);

            listContacts = (ViewGroup) rootView.findViewById(R.id.listContacts);

            TextView aux = new TextView(getActivity());

            aux.setText("Hello World!");

            listContacts.addView(aux);

            return rootView;
        }
    }

}

Внутри метода onCreateView() моего ContactListFragment я создаю TextView с текстом "Hello World".

Затем я пытаюсь добавить этот вид в мой ViewGroup listContacts.

Вот мой fragment_contacts.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="us.inevent.toot.Contacts$PlaceholderFragment" >

    <TextView
        android:id="@+id/textContact"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="0dp"
        android:text="@string/textContact"
        android:textSize="@dimen/abc_action_bar_title_text_size" />

    <ListView
        android:id="@+id/listContacts"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/textContact"
        android:layout_marginTop="10dp" />

</RelativeLayout>

Что я делаю неправильно?

Спасибо.