from kivy.uix.dropdown import DropDown
from kivy.uix.button import Button
from kivy.base import runTouchApp
# create a dropdown with 10 buttons
dropdown = DropDown()
for index in range(10):
# When adding widgets, we need to specify the height manually
# (disabling the size_hint_y) so the dropdown can calculate
# the area it needs.
btn = Button(text='Value %d' % index, size_hint_y=None, height=44)
# for each button, attach a callback that will call the select() method
# on the dropdown. We'll pass the text of the button as the data of the
# selection.
btn.bind(on_release=lambda btn: dropdown.select(btn.text))
# then add the button inside the dropdown
dropdown.add_widget(btn)
# create a big main button
mainbutton = Button(text='Hello', size_hint=(None, None))
# show the dropdown menu when the main button is released
# note: all the bind() calls pass the instance of the caller (here, the
# mainbutton instance) as the first argument of the callback (here,
# dropdown.open.).
mainbutton.bind(on_release=dropdown.open)
# one last thing, listen for the selection in the dropdown list and
# assign the data to the button text.
dropdown.bind(on_select=lambda instance, x: setattr(mainbutton, 'text', x))
runTouchApp(mainbutton)