def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.ui = Ui_main_window()
        self.ui.setupUi(self)
        self.ui.btnCheckin.clicked.connect(self.open_checkin)
        self.ui.btnCheckout.clicked.connect(self.open_checkout)
        self.checkin_window = self
        self.checkout_window = self
        self.felica_walker = FelicaWalker()

        style_prop_title_bar = settings.app['style']['title_bar']
        style_prop_ok_button = settings.app['style']['ok_button']

        self.ui.lblTitle.setStyleSheet("QLabel { " + style_prop_title_bar +
                                       " }")
        self.ui.btnCheckin.setStyleSheet("QPushButton { " +
                                         style_prop_ok_button + " }")
        self.ui.btnCheckout.setStyleSheet("QPushButton { " +
                                          style_prop_ok_button + " }")

        self.center()