title: Block all means to close an android application
body: <p>I'm trying to develop an application for an android tablet.</p>
  
  <p>This tablet will be shown to the public and they can touch it.</p>
  
  <p>I want to block all means to close the app except for a button/preference menu that requires a password.</p>
  
  <p>But after some research I am not sure if this is possible. 
  Long press on power button still works, home button too and return button.
  Will this work? if so how?</p>