__init__.py 文件源码

def add_widget(self, widget):
        if len(self.children) == 0:
            super(NavigationDrawer, self).add_widget(widget)
            self._side_panel = widget
        elif len(self.children) == 1:
            super(NavigationDrawer, self).add_widget(widget)
            self._main_panel = widget
        elif len(self.children) == 2:
            super(NavigationDrawer, self).add_widget(widget)
            self._join_image = widget
        elif self.side_panel is None:
            self._side_panel.add_widget(widget)
            self.side_panel = widget
        elif self.main_panel is None:
            self._main_panel.add_widget(widget)
            self.main_panel = widget
        else:
            raise NavigationDrawerException(
                'Can\'t add more than two widgets'
                'directly to NavigationDrawer')