NotificationPanel.java

@Override
    public boolean dispatchKeyEvent(KeyEvent event) {
    final int keyCode = event.getKeyCode();
        switch (keyCode) {
            // We exclusively handle the back key by hiding this panel.
            case KeyEvent.KEYCODE_BACK: {
                if (event.getAction() == KeyEvent.ACTION_UP) {
                    mBar.animateCollapsePanels();
                }
                return true;
            }
            // We react to the home key but let the system handle it.
            case KeyEvent.KEYCODE_HOME: {
                if (event.getAction() == KeyEvent.ACTION_UP) {
                    mBar.animateCollapsePanels();
                }
            } break;
        }
        return super.dispatchKeyEvent(event);
    }