Kivy:如何使用on_start : self.minimum_height创建小部件高度

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

class MyApp(App):
    def build(self):
        layout = BoxLayout(orientation='vertical')
        
        label1 = Label(text='Widget 1')
        layout.add_widget(label1)
        
        label2 = Label(text='Widget 2')
        layout.add_widget(label2)
        
        # 设置小部件的最小高度
        layout.bind(minimum_height=layout.setter('height'))
        
        return layout
    
    def on_start(self):
        # 在应用程序启动时执行的操作
        self.root.minimum_height = self.root.height

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