title: Service vs Runnable vs AsyncTask
body: <p>I'm developing a countdown timer app for Android. The app can show the remaining time. It has to be working even the phone is locked or the main activity is destroyed. I was wondering <em>which</em> of the following should I use and, more importantly, <em>why</em> should I use it (and <em>why not</em> the others).</p>
  
  <ul>
  <li>Service</li>
  <li>Runnable : A static reference to a Runnable object.  The reference is declared in an Activity class.</li>
  <li>AsyncTask</li>
  </ul>