title: Trying to center menu buttons
body: <p>I'm trying to have a menu of 2 buttons vertically.  I set the layout to RelativeLayout .  The first button is centered by
     android:layout_centerVertical="true"
          android:layout_centerHorizontal="true"
  which works.</p>
  
  <p>when I tried to add the second button to be under the first button by
   android:layout_toBottomOf="@+id/menuat"
  it gives me a error.</p>
  
  <p>How would I center more then one button on the screen?</p>
  
  <pre><code>&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:id="@+id/backFeetGallery"
      android:background="@drawable/background"
      android:layout_width="match_parent"
      android:layout_height="match_parent"&gt;
  
    &lt;Button
        android:id="@+id/menua"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:text="But A" 
    /&gt;
  
    &lt;Button
        android:id="@+id/menub"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:layout_toBottomOf="@+id/menuat"
        android:text="But B" 
    /&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>