Kivy按下按钮时，会创建一个新按钮，该按钮将显示在第二个屏幕上

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.screenmanager import ScreenManager, Screen

class FirstScreen(Screen):
    def on_enter(self):
        btn = Button(text='Create Button', size_hint=(None, None), size=(200, 50))
        btn.bind(on_press=self.create_button)
        self.add_widget(btn)

    def create_button(self, instance):
        new_btn = Button(text='New Button', size_hint=(None, None), size=(200, 50))
        self.manager.get_screen('second').add_widget(new_btn)

class SecondScreen(Screen):
    pass

class MyApp(App):
    def build(self):
        sm = ScreenManager()
        sm.add_widget(FirstScreen(name='first'))
        sm.add_widget(SecondScreen(name='second'))
        return sm

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