from kivy.app import App

from kivy.uix.boxlayout import BoxLayout

from kivy.lang.builder import Builder

"""Bubble本身不能触发事件，可以嵌套Button"""

Builder.load_string("""

<BubbleWidget>:

    size_hint:.5,.2

    pos_hint:{'center_x':.5,'center_y':.5}

    Bubble:

        arrow_pos:'bottom_left'

    Bubble:

        Button:

            text:'Bubble'

            on_release:root.pr()

""")

class BubbleWidget(BoxLayout):

    def __init__(self, **kwargs):

        super().__init__(**kwargs)

    def pr(self):

        print("123")

class MyApp(App):

    def build(self):

        return BubbleWidget()

if __name__ == '__main__':

    MyApp().run()