title: How to set system brightness of the buttons?
body: <p>I cannot find a way to control system (!) brightness of the buttons. I found this:</p>
  
  <blockquote>
    <p>public float <strong>buttonBrightness</strong></p>
    
    <p>This can be used to override the standard behavior of the button and
    keyboard backlights. A value of less than 0, the default, means to use
    the standard backlight behavior. 0 to 1 adjusts the brightness from
    dark to full bright.</p>
  </blockquote>
  
  <p>Link: <a href="http://developer.android.com/reference/android/view/WindowManager.LayoutParams.html#buttonBrightness" rel="nofollow">Android API reference</a></p>
  
  <p>Please note "override the standard behavior", this indicates that there is some standard behaviour settings. But I cannot find any API for that.</p>
  
  <p>I would like to execute such code (from my service):</p>
  
  <pre><code>previous = get_buttons_brightness();
  set_buttons_brightness(0); // off
  ...
  set_buttons_brightness(previous);
  ...
  </code></pre>