如何在奇异果中获得AnchorLayout孩子的身高？

from kivy.app import App
from kivy.uix.anchorlayout import AnchorLayout
from kivy.uix.button import Button

class AnchorLayoutApp(App):
    def build(self):
        layout = AnchorLayout()
        
        # 添加孩子元素
        button = Button(text='Hello World')
        layout.add_widget(button)
        
        # 获取孩子元素的身高
        child_height = button.height
        print("孩子元素的身高为：", child_height)
        
        return layout

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