use a proxy widget to animate items of a recycleview without leaking on other widgets.

rv_animate_items.py

from copy import copy

from kivy.app import App
from kivy.clock import triggered
from kivy.lang import Builder
from kivy.animation import Animation
from kivy.factory import Factory as F
from kivy.properties import (
    ObjectProperty, ListProperty
)


KV = '''
<Item>:
    index: None
    animation_proxy: None
    on_release: app.animate_item(self.index)


RecycleView:
    data: app.data
    viewclass: 'Item'
    RecycleBoxLayout:
        orientation: 'vertical'
        size_hint: 1, None
        height: self.minimum_height
        default_size_hint: 1, None
        default_size: 0, dp(40)
'''

class Item(F.Button):
    animation_proxy = ObjectProperty(allownone=True)
    _animation_proxy = None

    def update_opacity(self, proxy, opacity):
        self.opacity = opacity

    def on_animation_proxy(self, *args):
        if self._animation_proxy:
            self._animation_proxy.unbind(opacity=self.update_opacity)

        self._animation_proxy = self.animation_proxy
        if self.animation_proxy:
            self.opacity = self.animation_proxy.opacity
            self.animation_proxy.bind(opacity=self.update_opacity)
        else:
            self.opacity = 1


class Application(App):
    data = ListProperty()

    def build(self):
        self.data = [
            {'index': i, 'text': 'hello {}'.format(i), 'animation_proxy': None}
            for i in range(1000)
        ]
        return Builder.load_string(KV)

    def update_time(self, dt):
        self.time += dt

    @triggered(timeout=0.05)
    def animate_item(self, index):
        proxy = F.Widget(opacity=1)
        item = copy(self.data[index])
        animation = (
            Animation(opacity=0, d=.1, t='out_quad')
            + Animation(opacity=1, d=5, t='out_quad')
        )
        animation.bind(on_complete=lambda *x: self.reset_animation(item))
        item['animation_proxy'] = proxy
        self.data[index] = item
        animation.start(proxy)

    def reset_animation(self, item):
        # animation is complete, widget should be collected
        item['animation_proxy'] = None


if __name__ == "__main__":
    Application().run()