Try this..
Remove android:layout_alignParentTop="true"
and android:layout_gravity="center_horizontal"
and add android:layout_centerInParent="true"
<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" >
<ProgressBar
android:id="@+id/progressBar1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:visibility="invisible" />
<ListView
android:id="@android:id/list"
android:layout_width="match_parent"
android:layout_height="fill_parent" >
</ListView>
</RelativeLayout>