如何在Kivy中切换小部件的动画过渡

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

class MyWidget(BoxLayout):
    def __init__(self, **kwargs):
        super(MyWidget, self).__init__(**kwargs)
        
        self.orientation = 'vertical'
        
        self.button1 = Button(text='Button 1')
        self.button1.bind(on_release=self.animate_transition)
        self.add_widget(self.button1)
        
        self.button2 = Button(text='Button 2', opacity=0)
        self.add_widget(self.button2)
        
    def animate_transition(self, *args):
        anim1 = Animation(opacity=0, duration=0.5)
        anim1.bind(on_complete=self.switch_buttons)
        anim1.start(self.button1)
        
        anim2 = Animation(opacity=1, duration=0.5)
        anim2.start(self.button2)
        
    def switch_buttons(self, *args):
        self.remove_widget(self.button1)
        self.add_widget(self.button1)
        
class MyApp(App):
    def build(self):
        return MyWidget()

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