setSystemUiVisibility(SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION) does not work

Hmm apparently I duplicated my own question! But anyway I found the answer: After reading the source code - which is often the only way to find things out in Android-land - I discovered the following undocumented fact:

setSystemUiVisibility() only has effect when the view you call it from is visible!

Even more: The view in which you call setSystemUiVisibility() must remain visible for the nav bar to remain hidden. Thanks for documenting that guys, really great.

Here is the relevant code, in View.java.

void performCollectViewAttributes(AttachInfo attachInfo, int visibility) {
    if ((visibility & VISIBILITY_MASK) == VISIBLE) {
        if ((mViewFlags & KEEP_SCREEN_ON) == KEEP_SCREEN_ON) {
            attachInfo.mKeepScreenOn = true;
        }
        attachInfo.mSystemUiVisibility |= mSystemUiVisibility;
        ListenerInfo li = mListenerInfo;
        if (li != null && li.mOnSystemUiVisibilityChangeListener != null) {
            attachInfo.mHasSystemUiListeners = true;
        }
    }
}

I use setOnSystemUiVisibilityChangeListener() to make this full screen mode work for me including hiding the navigation bar.

@Override
protected void onResume() {
    if (Build.VERSION.SDK_INT >= 16) {
        getWindow().getDecorView().setOnSystemUiVisibilityChangeListener(
                new OnSystemUiVisibilityChangeListener() {
                    @Override
                    public void onSystemUiVisibilityChange(int visibility) {
                        if ((visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0) {
                            getActionBar().show();
                        } else {
                            int mUIFlag = View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                                    | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                                    | View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                                    | View.SYSTEM_UI_FLAG_LOW_PROFILE
                                    | View.SYSTEM_UI_FLAG_FULLSCREEN
                                    | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION;
                            getWindow().getDecorView()
                                    .setSystemUiVisibility(mUIFlag);
                            getActionBar().hide();
                        }
                    }
                });
    }

    super.onResume();
}

it seems that android only trigger the setSystemUiVisibility() when inside the listener.

I implemented this as below however I get a blank gap at the bottom (see screenshot)

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    if (hasFocus) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            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_LOW_PROFILE
                            | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION // hide nav bar
                            | View.SYSTEM_UI_FLAG_FULLSCREEN // hide status bar
                            | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
            );
        }
    }
}