正在尝试调整文本输入的大小。(Kivy，QPython，Android)。但是不确定如何正确地编写代码

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.textinput import TextInput

class MyBoxLayout(BoxLayout):
    def __init__(self, **kwargs):
        super(MyBoxLayout, self).__init__(**kwargs)
        
        # 创建文本输入框
        self.text_input = TextInput(text='Hello World', font_size=20)
        
        # 添加文本输入框到布局中
        self.add_widget(self.text_input)

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

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