expanding_list_element.py

from kivy.app import App
from kivy.lang import Builder
from kivy.clock import Clock
from kivy.animation import Animation

# Expands an element in a grid and adds a widget to it/
kv = """
<AnimatedListTile@FloatLayout>:
    canvas.before:
        Color:
            rgb: 1,1,1
        Rectangle:
            size: self.size
            pos: self.pos
            
    animated: False
    Label:
        text: "Hello"
        color: (0,0,0,1)
        size_hint: 1, 1 if not root.animated else .5
        pos_hint: {"top": 1, "right": 1}
    Button:
        text: "A button"
        size_hint: 1, .5
        pos_hint: {"top": .5, "right": 1 if root.animated else 100}

GridLayout:
    cols: 1
    spacing: 10,
    padding: 10,
    AnimatedListTile:
        size_hint: 1, .1
        pos_hint: {"center_x": .5, "center_y": .5}
    AnimatedListTile:
        id: animated_widget
        size_hint: 1, .1
        pos_hint: {"center_x": .5, "center_y": .5}
    AnimatedListTile:
        size_hint: 1, .1
        pos_hint: {"center_x": .5, "center_y": .5}
    AnimatedListTile:
        size_hint: 1, .1
        pos_hint: {"center_x": .5, "center_y": .5}
    AnimatedListTile:
        size_hint: 1, .1
        pos_hint: {"center_x": .5, "center_y": .5}
    
"""

kv = Builder.load_string(kv)

class MainApp(App):
    def build(self):
        return kv

    def on_start(self):
        Clock.schedule_interval(self.animate, 2)

    def animate(self, *args):
        anim = Animation(size_hint_y=.3)
        anim.bind(on_complete=self.reset_anim)
        self.root.ids.animated_widget.animated = True
        anim.start(self.root.ids.animated_widget)

    def reset_anim(self, *args):
        widget = self.root.ids.animated_widget
        widget.size_hint_y = .1
        self.root.ids.animated_widget.animated = False

MainApp().run()