Python kivy更新不同屏幕中的标签文本

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.screenmanager import ScreenManager, Screen

class Screen1(Screen):
    pass

class Screen2(Screen):
    pass

sm = ScreenManager()
sm.add_widget(Screen1(name='screen1'))
sm.add_widget(Screen2(name='screen2'))

class Screen1(Screen):
    def __init__(self, **kwargs):
        super(Screen1, self).__init__(**kwargs)
        self.label = Label(text='Screen 1 Label')
        self.add_widget(self.label)

class Screen2(Screen):
    def __init__(self, **kwargs):
        super(Screen2, self).__init__(**kwargs)
        self.label = Label(text='Screen 2 Label')
        self.add_widget(self.label)

# 通过屏幕名称获取屏幕对象
screen1 = sm.get_screen('screen1')
screen2 = sm.get_screen('screen2')

# 更新标签文本
screen1.label.text = 'New Text for Screen 1'
screen2.label.text = 'New Text for Screen 2'