在弹出确认后，kivy将值从一个屏幕传递到另一个屏幕

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.popup import Popup
from kivy.properties import StringProperty

class FirstScreen(Screen):
    value = StringProperty("")  # 存储传递的值

    def show_confirmation(self):
        # 创建一个弹出窗口
        popup = Popup(title='确认', content=Label(text='确定要传递该值吗？'),
                      size_hint=(None, None), size=(400, 200))

        # 创建确认和取消按钮
        confirm_button = Button(text='确认', on_release=self.confirm)
        cancel_button = Button(text='取消', on_release=popup.dismiss)

        # 将按钮添加到弹出窗口的内容中
        popup.content.add_widget(confirm_button)
        popup.content.add_widget(cancel_button)

        # 显示弹出窗口
        popup.open()

    def confirm(self, instance):
        # 存储传递的值
        self.value = "传递的值"

        # 切换到第二个屏幕
        self.manager.current = 'second'

class SecondScreen(Screen):
    def on_pre_enter(self):
        # 获取第一个屏幕的实例
        first_screen = self.manager.get_screen('first')

        # 获取传递的值
        value = first_screen.value

        # 在第二个屏幕中显示传递的值
        self.add_widget(Label(text=value))

class MyApp(App):
    def build(self):
        # 创建屏幕管理器
        sm = ScreenManager()

        # 添加第一个屏幕
        first_screen = FirstScreen(name='first')
        sm.add_widget(first_screen)

        # 添加第二个屏幕
        second_screen = SecondScreen(name='second')
        sm.add_widget(second_screen)

        return sm

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