title: How to make the android Home Launcher with transparent background (not opaque)
body: <p>I'll trying to developing the home launcher with transparent background. So, the view of previous executing app go to the background of home launcher, and it is continuously running. 
  In other words, without stopping the previous app, while still running a app, the home launcher with transparent background is running on it.</p>
  
  <p>Can i make a this feature by using just Android SDK?
  If it need a modify to the Android Framework, please, advise to me how to modify and which source code.</p>