Kivy弹出窗口出现在函数运行之后，而不是之前

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.popup import Popup
from kivy.clock import Clock

class MyApp(App):
    def build(self):
        button = Button(text='Click me')
        button.bind(on_release=self.show_popup)
        return button

    def show_popup(self, instance):
        popup = Popup(title='Popup Window', content=Button(text='Close me'), size_hint=(None, None), size=(400, 400))
        Clock.schedule_once(lambda dt: popup.open())  # 使用时钟调度函数显示弹出窗口

MyApp().run()