Android : List view - auto modify height

I'm learning Android and now I have this tutorial: http://www.informit.com/articles/article.aspx?p=1928230

I modify (I want scroll all page) this and i have:

<?xml version="1.0" encoding="utf-8"?>
<ScrollView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/ScrollView01"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" >

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical" >


        <ListView
            android:id="@+id/petList"
            android:layout_width="wrap_content"
            android:layout_height="700dp" //here!!!!
            android:divider="#000"
        />

        <Button
            android:id="@+id/ButtonAddNews"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="Add new Pet" >
        </Button>
    </LinearLayout>

</ScrollView>

Single item:

         <LinearLayout
            android:id="@+id/relative"
            android:layout_height="wrap_content"  
            android:layout_width="fill_parent"
            android:padding="5dp"
            orientation="horizontal">
                    <TextView
                        android:id="@+id/TextView01"
                        android:layout_width="match_parent"
                        android:layout_weight="1"
                        android:layout_height="?android:attr/listPreferredItemHeight"
                        android:textColor="#f00"
                        android:layout_alignParentLeft="true"
                        android:text="two" ></TextView>
                    <TextView
                        android:id="@+id/TextView02"
                        android:layout_width="match_parent"
                        android:layout_weight="1"
                        android:layout_height="?android:attr/listPreferredItemHeight"
                        android:textColor="#f00"
                        android:text="three" 
                        android:layout_alignParentRight="true"></TextView>
        </LinearLayout>

This working ok, but i must modify android:layout_height.

For example if i have 3 item in list then 700dp it is too more. If I use fill_parent, match_parent or wrap_content then this show me only one item (I can scroll it).

What I have to type in the layout_height to automatically expanding, with the number of items?