from kivy.app import App
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.animation import Animation
from kivy.core.window import Window
from kivy.metrics import dp
from kivy.clock import Clock, mainthread
from kivy.properties import BooleanProperty, ListProperty

Window.size = 400, 600

kv = r'''
PullDown:
    orientation:"vertical"
    Label:
        id:btn
        text:"Expandable Label"
        size_hint_y: None
        height:0
        opacity:0
    RecycleView:
        id:rv
        data: root.data
        viewclass:"Button"
        effect_cls: 'ScrollEffect'
        RecycleGridLayout:
            id:bl
            cols:3
            default_size_hint: 1, None
            default_height: dp(101)
            size_hint_y: None
            size: self.minimum_size
'''


class PullDown(BoxLayout):
    rv_open = BooleanProperty(False)  # used to create an event
    data = ListProperty([{'text': str(x)} for x in range(18)])

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self._animation_ongoing = False

    def on_touch_down(self, touch):
        if self.collide_point(*touch.pos):
            touch.grab(self)
        if self.rv_open:
            self.collapse(touch)
        return super().on_touch_down(touch)

    def on_touch_move(self, touch):
        if (touch.grab_current is self) and (not self._animation_ongoing):
            if touch.dy < -10:
                self.expand(touch)
                return super().on_touch_up(touch)
        if self._animation_ongoing:
            return True
        return super().on_touch_move(touch)

    def on_touch_up(self, touch):
        if touch.grab_current is self:
            touch.ungrab(self)
        return super().on_touch_up(touch)

    # @mainthread
    def expand(self, touch):
        self._animation_ongoing = True
        # super().on_touch_up(touch)
        anim = Animation(
            height=dp(100),
            opacity=1,
            d=0.3, t="out_cubic"
        )

        def on_animation_complete(*args):
            self._animation_ongoing = False
            self.rv_open = True

        anim.bind(on_complete=on_animation_complete)
        anim.start(self.ids.btn)

    # @mainthread
    def collapse(self, touch):
        self._animation_ongoing = True
        anim = Animation(
            height=0,
            opacity=0,
            d=0.3, t="out_cubic"
        )

        def on_animation_complete(*args):
            self._animation_ongoing = False
            self.rv_open = False
            self.ids.rv.scroll_y = 1  # set scroll_y to None

        anim.bind(on_complete=on_animation_complete)
        anim.start(self.ids.btn)


class Test(App):
    def build(self):
        self.title = 'Pull down touch'
        return Builder.load_string(kv)


Test().run()