title: ?android:attr/selectableItemBackground
body: <p>when writing my android app i used</p>
  
  <pre><code>android:background="?android:attr/selectableItemBackground"
  </code></pre>
  
  <p>I tried looking for attr.xml file that would be containing the source but i could not find it. Any ideas please on where i can find it. I found one attr.xml in </p>
  
  <blockquote>
    <p>C:\Program Files (x86)\Android\android-sdk\platforms\android-13\data\res\values</p>
  </blockquote>
  
  <p>but it did not have the attribute mentioned above. Can anyone lead me where I can find the xml resource with the attribute above?</p>