title: How to hide my application but not close/finish it
body: <p>I would like to let user to leave my application by hiding it but not finishing it.</p>
  
  <p>I could call finish() in my main activity, but it takes some time to do that. It's not good for user experience, therefore a better choice might be to hide it. Just I don't know how to achieve it.</p>
  
  <p>Thanks for all the answer. </p>
  
  <hr>
  
  <p>I am not trying to do something in the background, because I already have a service. </p>
  
  <p>In my application, user might press an button to close my main activity. However, it take a little time to do that. At least after 0.5 sec, then I'll see my application disappear on screen. </p>
  
  <p>However, if I press home key. My application is disappear immediately, so it's the effect I need.</p>