交换小部件/用on_touch_down()替换Kivy中的布局

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

class SwapWidget(BoxLayout):
    def on_touch_down(self, touch):
        if self.collide_point(*touch.pos):
            for child in self.children:
                if child.collide_point(*touch.pos):
                    self.remove_widget(child)
                    self.add_widget(child, index=0)  # 将被点击的小部件移动到布局的第一个位置
                    break
        return super().on_touch_down(touch)

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

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