kivy:如何在FloatLayout中定位滚动标签？

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.scrollview import ScrollView
from kivy.uix.label import Label

class MyFloatLayout(FloatLayout):
    pass

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

class MyFloatLayout(FloatLayout):
    def __init__(self, **kwargs):
        super(MyFloatLayout, self).__init__(**kwargs)
        
        # 创建ScrollView和Label组件
        scroll_view = ScrollView()
        label = Label(text="这是一个滚动标签")
        
        # 将Label添加到ScrollView中
        scroll_view.add_widget(label)
        
        # 将ScrollView添加到FloatLayout中，并设置位置和大小
        self.add_widget(scroll_view)
        scroll_view.pos_hint = {'center_x': 0.5, 'center_y': 0.5}
        scroll_view.size_hint = (0.8, 0.8)

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