java - How to hide or block the navigation bar or 3 main button

Question

I know that there are many many posts for my question , but they don't work really, as I've tried many solutions.

I would like that my title Bar (1) stays on the top normally AND my navigation bar (2) is hidden or blocked. I'm developing an application where the back button, home button, and app button are not allowed to be clicked. (the three buttons are locked or hidden) I already use :

@Override
        public void onBackPressed() {
            getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LOW_PROFILE);
            getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
        }           

But the other buttons stay available. Please see the attached picture to get a better understanding.

Click here to see my screenshot