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58 lines
1.9 KiB
Markdown
58 lines
1.9 KiB
Markdown
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RouletteScrollEffect
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===================
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This is a subclass of `kivy.effects.ScrollEffect` that simulates the
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motion of a roulette, or a notched wheel (think Wheel of Fortune). It is
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primarily designed for emulating the effect of the iOS and android date pickers.
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Usage
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-----
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Here's an example of using `RouletteScrollEffect` for a `kivy.uix.scrollview.ScrollView`:
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```python
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from kivy.uix.gridlayout import GridLayout
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from kivy.uix.button import Button
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from kivy.uix.scrollview import ScrollView
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# Preparing a `GridLayout` inside a `ScrollView`.
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layout = GridLayout(cols=1, padding=10, size_hint=(None, None), width=500)
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layout.bind(minimum_height=layout.setter('height'))
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for i in range(30):
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btn = Button(text=str(i), size=(480, 40), size_hint=(None, None))
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layout.add_widget(btn)
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root = ScrollView(
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size_hint=(None, None),
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size=(500, 320),
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pos_hint={'center_x': .5, 'center_y': .5},
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do_scroll_x=False,
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)
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root.add_widget(layout)
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# Preparation complete. Now add the new scroll effect.
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root.effect_y = RouletteScrollEffect(anchor=20, interval=40)
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runTouchApp(root)
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```
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Here the `ScrollView` scrolls through a series of buttons with height `40`. We then attached a `RouletteScrollEffect` with interval 40,
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corresponding to the button heights. This allows the scrolling to stop at
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the same offset no matter where it stops. The `RouletteScrollEffect.anchor`
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adjusts this offset.
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Customizations
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--------------
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Other settings that can be played with include:
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- `RouletteScrollEffect.pull_duration`
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- `RouletteScrollEffect.coasting_alpha`
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- `RouletteScrollEffect.pull_back_velocity`
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- `RouletteScrollEffect.terminal_velocity`
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See their module documentations for details.
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`RouletteScrollEffect` has one event ``on_coasted_to_stop`` that
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is fired when the roulette stops, "making a selection". It can be listened to
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for handling or cleaning up choice making.
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