title: Force lost focus
body: <p>Consider an activity with a few buttons.</p>
  
  <p>We can dynamically assign the focus this way:</p>
  
  <pre><code>b1.requestFocus();
  </code></pre>
  
  <p>If the user double taps the button, I want force a <em>loss</em> of focus.</p>
  
  <p>How could I do that?</p>