title: onSharedPreferenceChanged and PreferenceFragment
body: <p>Trying to follow the examples given in <a href="http://developer.android.com/guide/topics/ui/settings.html" rel="nofollow">http://developer.android.com/guide/topics/ui/settings.html</a> but finding it difficult as it arbitrarily flips between using and not using fragments.</p>
  
  <p>I've taken its advice to use fragments when implementing Preferences for my app as I'm using the most recent SDK (16)</p>
  
  <p>I'm trying to implement <code>onSharedPreferenceChanged</code> method such that I can update the preference summaries when a user chages a preference value.</p>
  
  <p>should I implement the callback method in the fragment or the parent Activity?</p>