Stretching across 2 rows in Table Layout

How do I stretch across 2 columns in the TableLayout. I have 2 rows with a label and edit text on 1 row and I want to have a single button stretch across the whole second row.

<?xml version="1.0" encoding="utf-8"?>
<TableLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="fill_parent" 
    android:layout_width="fill_parent"
    android:background="#000000"
    android:stretchColumns="1">

    <TableRow>
        <TextView
            android:text = "Name: "  />
        <EditText
            android:id = "@+id/txtAddName"
            android:gravity = "right"
            android:layout_width = "fill_parent" />
    </TableRow>
    <TableRow>
        <TextView
            android:text = "Phone: "  />
        <EditText
            android:id = "@+id/txtAddPhone"
            android:gravity = "right"
            android:layout_width = "fill_parent" />        
    </TableRow>
    <TableRow>
        <Button
            android:id = "@+id/btnAdd"
            android:text = "Add Entrie"
            android:layout_width = "fill_parent" />
    </TableRow>
    <TableRow>
        <Button
            android:开发者_高级运维id = "@+id/btnShow"
            android:text = "Show all Entries"
            android:layout_width = "fill_parent" />
    </TableRow>
    <TableRow>
        <Button
            android:id = "@+id/btnDelete"
            android:text = "Delete all Entries"
            android:layout_width = "fill_parent" />
    </TableRow>
</TableLayout>

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check here an example: http://www.droidnova.com/tablelayout-supports-column-span,105.html