kv 20 floatlayout 1

#float.py

from kivy.app import App

from kivy.base import runTouchApp

from kivy.uix.widget import Widget

class Float(Widget):

    pass

class FloatApp(App):

    def build(self):

        return Float()

FloatApp().run()

--------------------

#float.kv

<Button>:

    font_size:40

    color:0.3, 0.6, 0.7, 1

    size_hint: 0.5, 0.5

<Float>:

    FloatLayout:

        size: root.width, root.height

        Button:

            pos_hint: {"x": 0.5, "top": 1}

            text: "Button"

        Button:

            id: btn

            pos_hint: {"y": 0}

            text: "up" if btn.state == "normal" else "down"

            background_color: 0.3, 0.4, 0.5, 1

reference:

https://www.youtube.com/watch?v=lnOTAq4NQfQ