在多个kivymd窗口中更改背景

from kivymd.app import MDApp
from kivymd.uix.screen import MDScreen
from kivymd.uix.button import MDFlatButton

class MyApp(MDApp):
    def build(self):
        self.theme_cls.primary_palette = "BlueGray"
        self.theme_cls.theme_style = "Dark"

        # 创建多个屏幕
        screen1 = MDScreen(name="screen1")
        screen2 = MDScreen(name="screen2")

        # 创建按钮，用于切换屏幕
        button1 = MDFlatButton(text="切换到屏幕1", on_release=self.switch_screen)
        button2 = MDFlatButton(text="切换到屏幕2", on_release=self.switch_screen)

        # 将按钮添加到屏幕中
        screen1.add_widget(button1)
        screen2.add_widget(button2)

        # 将屏幕添加到应用中
        self.root.add_widget(screen1)
        self.root.add_widget(screen2)

    def switch_screen(self, instance):
        # 切换到指定的屏幕
        if instance.text == "切换到屏幕1":
            self.root.current = "screen1"
        elif instance.text == "切换到屏幕2":
            self.root.current = "screen2"

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