android:layout_below

Force the control located below another control as follows:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    

                xmlns:tools="http://schemas.android.com/tools"    

                android:layout_width="fill_parent"    

                android:layout_height="fill_parent"    

                android:orientation="vertical" >
    <Button android:id="@+id/button1"

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

            android:text="@string/button1" />
    <Button android:id="@+id/button2"

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

           android:layout_below="@id/button1"
           android:text="@string/button2" />
    <TextView android:id="@+id/textView1"

              android:layout_width="match_parent"

              android:layout_height="match_parent"

             android:layout_below="@id/button2"/>

</RelativeLayout>