更新kivy上的标签

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.boxlayout import BoxLayout

class MyBoxLayout(BoxLayout):
    def __init__(self, **kwargs):
        super(MyBoxLayout, self).__init__(**kwargs)
        self.label = Label(text="初始文本")
        self.add_widget(self.label)

class MyApp(App):
    def build(self):
        return MyBoxLayout()

class MyApp(App):
    def build(self):
        return MyBoxLayout()

    def update_label_text(self, new_text):
        self.root.label.text = new_text

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

MyApp().update_label_text("新的文本")