title: How to close Android application?
body: <p>I want to close my application, so that it no longer runs in the background.</p>
  
  <p>How to do that? Is this good practice on Android platform?</p>
  
  <p>If I rely on the "back" button, it closes the app, but it stays in background. There is even application called "TaskKiller" just to kill those apps in the background.</p>