Python和Kivy -显示/隐藏框

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button

class MyBoxLayout(BoxLayout):
    def __init__(self, **kwargs):
        super(MyBoxLayout, self).__init__(**kwargs)
        
        self.button = Button(text='Toggle Content')
        self.button.bind(on_release=self.toggle_content)
        self.add_widget(self.button)
        
        self.content = BoxLayout(orientation='vertical')
        self.add_widget(self.content)
        
        self.visible = False
        
    def toggle_content(self, instance):
        if self.visible:
            self.content.clear_widgets()
            self.visible = False
        else:
            self.content.add_widget(Button(text='Hidden Content'))
            self.visible = True

class MyApp(App):
    def build(self):
        return MyBoxLayout()

if __name__ == '__main__':
    MyApp().run()