animation scroll

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.scrollview import ScrollView
from kivy.uix.button import Button
from kivy.animation import Animation

kv = """
<ScrollButton>:
    size_hint_y: None
    height: dp(48)
    on_release: print(f'{self.text} pressed')

BoxLayout:
    orientation: 'vertical'
    spacing: dp(10)
    Label:
        text: 'Example of ScrollView Animation'
        size_hint_y: None
        height: 30
    AnimScrollView:
        id: sv
        effect_cls: 'ScrollEffect' # Use 'ScrollEffect', 'DampedScrollEffect' or 'OpacityScrollEffect'
        BoxLayout:
            orientation: 'vertical'
            id: box
            size_hint_y: None
            height: self.minimum_height
    ToggleButton:
        size_hint_y: None
        height: dp(48)
        on_state:
            sv.animate_scroll(self.state)
            self.text = {'normal': 'Start', 'down': 'Stop'}[self.state]
        text: 'Start'
"""


class ScrollButton(Button):
    pass

class AnimScrollView(ScrollView):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.anim = Animation(scroll_y=0, duration=15) + Animation(scroll_y=1, duration=5)
        self.anim.repeat = True

    def animate_scroll(self, toggle_state):
        if toggle_state == 'down':
            self.anim.start(self)
        else:
            self.anim.stop(self)


class ScrollViewExampleApp(App):
    def build(self):
        return Builder.load_string(kv)

    def on_start(self):
        # create buttons in the boxlayout that is in the scrollview
        for i in range(20):
            self.root.ids.box.add_widget(ScrollButton(text=f'Button {i}'))




ScrollViewExampleApp().run()