Show PopupWindow in Immersive Sticky mode

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private PopupWindow mPopupWindow;

    @Override protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        int windowWidth = 480;
        int windowHeight = 120;

        TextView popupView = (TextView) LayoutInflater.from(getApplicationContext())
                .inflate(android.R.layout.simple_list_item_1, null);
        popupView.setText("PopupWindow");
        popupView.setGravity(Gravity.CENTER);
        popupView.setBackgroundColor(Color.BLACK);
        popupView.setOnClickListener(new View.OnClickListener() {
            @Override public void onClick(View v) {
                Toast.makeText(getApplicationContext(), "PopupWindow Click", Toast.LENGTH_SHORT)
                        .show();
            }
        });

        mPopupWindow = new PopupWindow(popupView, windowWidth, windowHeight);
        mPopupWindow.setFocusable(false);
        mPopupWindow.setBackgroundDrawable(new ColorDrawable());
        mPopupWindow.setOutsideTouchable(true);

        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override public void onClick(View v) {
                if (!mPopupWindow.isShowing()) {
                    showPopup(v);
                } else {
                    mPopupWindow.dismiss();
                }
            }
        });
    }

    @Override public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        if (hasFocus) {
            fullScreenImmersive(getWindow());
        }
    }

    public void showPopup(View anchor) {
        mPopupWindow.setFocusable(false);
        mPopupWindow.update();

        PopupWindowCompat.showAsDropDown(mPopupWindow, anchor,
                -mPopupWindow.getWidth() / 2 + anchor.getWidth() / 2,
                -mPopupWindow.getHeight() - anchor.getHeight(), Gravity.CENTER);

        fullScreenImmersive(mPopupWindow.getContentView());
        mPopupWindow.setFocusable(true);
        mPopupWindow.update();
    }

    public void fullScreenImmersive(Window window) {
        if (window != null) {
            fullScreenImmersive(window.getDecorView());
        }
    }

    public void fullScreenImmersive(View view) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            int uiOptions = View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                    | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                    | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                    | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
                    | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                    | View.SYSTEM_UI_FLAG_FULLSCREEN;
            view.setSystemUiVisibility(uiOptions);
        }
    }
}