ScrollView
needs only one child ViewGroup which will contain other child views. And as your hint said: "The parent RelativeLayout is useless" indeed, because now you can have only the ScrollView and set to it the background:
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/hp_instr" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:text="@string/instr"
android:textColor="#FFFFFF"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
</ScrollView>
NOTE: A last thing to know, when you'll use a ScrollView, the child ViewGroup (LinearLayout, RelativeLayout, TableLayout, whatever) must to declare its height to wrap_content
because the height expands regarding its content (same for HorizontalScrollView
but for the width).