如何使用屏幕上的类继承在kivy中创建按钮

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout

# 自定义按钮类
class CustomButton(Button):
    def __init__(self, **kwargs):
        super(CustomButton, self).__init__(**kwargs)
        self.text = '点击我'
        self.background_color = (0.2, 0.6, 1, 1)  # 设置背景颜色
        self.bind(on_press=self.on_button_press)  # 绑定点击事件

    def on_button_press(self, instance):
        print('按钮被按下!')

# 主应用类
class MyApp(App):
    def build(self):
        layout = BoxLayout(orientation='vertical')
        custom_btn = CustomButton()
        layout.add_widget(custom_btn)
        return layout

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