How to hide navigation bar permanently in android activity?

I want to conceal navigation bar enduringly in my activity(not whole system ui). now I am using this piece of code

getWindow().getDecorView().setSystemUiVisibility(View].SYSTEM_UI_FLAG_HIDE_NAVIGATION);

It hide the bar but when user touches the screen it showing again. Is there is any way to hide it enduringly until activity onStop();I refered some sites like (http://usawriters.org/).But Didn't get answer