Cannot hide navigation bar from inside a fragment

Question

I currently have a ViewPager with a FragmentStatePagerAdapter. The problem here is that a navigation bar appears whenever I click a button, so I started manually hiding it with the following code:

getWindow().getDecorView().setSystemUiVisibility(
                                View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                                        | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                                        | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                                        | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                                        | View.SYSTEM_UI_FLAG_FULLSCREEN
                                        | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);

This code snippet works fine inside an activity, but doesn't do anything in a fragment. For all similar stackoverflow answers, they recommend to add getActivty() like below:

getActivity().getWindow().getDecorView()………..

BUT FOR SOME REASON IT IS STILL NOT HIDING THE NAVIGATION BAR

Answer 1

After failing for a couple of days to solve this problem, I finally decided to go back and read the android documentation. So I solved the problem by enabling sticky immersive mode whenever activity's window focus is changed, like below:

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
// I removed the below condition check because I still want to hide System UI even if activity
// loses focus. Such cases include spinner dropdown list is open, dialog box is displayed, etc.
// if(hasFocus)
    hideSystemUI();
}

private void hideSystemUI() {
    // Enables sticky immersive mode.
    // For "lean back" mode, remove SYSTEM_UI_FLAG_IMMERSIVE_STICKY.
    // Or for "regular immersive," replace it with SYSTEM_UI_FLAG_IMMERSIVE
    View decorView = getWindow().getDecorView();
    decorView.setSystemUiVisibility(
                    View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
                    // Set the content to appear under the system bars so that the
                    // content doesn't resize when the system bars hide and show.
                    | View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                    | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                    // Hide the nav bar and status bar
                    | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                    | View.SYSTEM_UI_FLAG_FULLSCREEN);
}

// Shows the system bars by removing all the flags
// except for the ones that make the content appear under the system bars.
private void showSystemUI() {
    View decorView = getWindow().getDecorView();
    decorView.setSystemUiVisibility(
            View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                    | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                    | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
}

Note: The reason why I enabled sticky immersive mode instead of the regular immersive mode is that with regular immersive mode, non-translucent navigation bar will be permanently displayed when user gestures from bottom to top. But with sticky immersive mode, a translucent navigation bar will be temporarily displayed.

Update: I forgot to link this to the question. Since the onWindowFocusChanged(boolean hasFocus) will be triggered even if the focus changes are caused by a fragment task, there is no need to hide the System UI from inside the fragment.