[Python] Kivy: RecycleView calls __init__ before data is set, and seems to reset size to...

I have a RecycleView. Its viewclass is a class that extends Button. An initial basic example I made is working, except 1. some initializiation data is not displayed and 2. the buttons are resized (to (100, 100) — I’m guessing that’s a Button size default).

class InventoryIngredientButton(Button):
count = NumericProperty(None)
display_count = StringProperty(None)

def __init__(self, inventory_ingredient: InventoryIngredient = ing1, **kwargs):
print("init is being called")
super().__init__(
background_normal=inventory_ingredient.ingredient.icon_img,
text=inventory_ingredient.ingredient.display_name,
size_hint=(None, None),
size=(200, 200),
**kwargs)

def use(self):
self.count -= 1
self.display_count = str(self.count)

def on_count(self, instance, value):
# print size for debugging
print("count is %s and size is %s" % (value, self.size))
if value == 0:
self.disabled = True

# for debugging
def on_size(self, instance, value):
print("Size changed to value %s for button %s" % (value, self.count))




class RV(RecycleView):
def __init__(self):
super().__init__()

# 1. count is respected, inventory_ingredient is not:
# 2. If you add “’size’: (200, 200)” to the dictionaries then buttons aren’t resized:
self.data = [{'inventory_ingredient': ing2, 'count': 6}, {'count': 3, 'inventory_ingredient': ing1}]


.tutorial_listview.kv file:

<InventoryIngredientButton>
pos: self.x, self.y
pos_hint: None, None
count: 1
on_press: root.use()

Label:
text: str(root.count)
pos: root.x-10,root.y-10
pos_hint: None, None

<RV>:
viewclass: 'InventoryIngredientButton'
RecycleBoxLayout:
rows: 2
cols: 5
size_hint: 1, 1
pos_hint: 0, 0


Runner included for completeness:

class RecycleTutorialApp(App):
def build(self):
return RV()


if __name__ == "__main__":
Builder.load_file('tutorial_listview.kv')
RecycleTutorialApp().run()


The print logs indicate that the buttons are initialized with default values. Then, when self.data is set, count is overwritten to the displayed value. However, unless I explicitly set size, size=(100,100) seems to reset next and resizes the button. inventory_ingredient is also ignored because __init__ has already been called.

Logs show init is called, then count is changed, then size:

init is being called and type is Lemon (Lemon is the default)
Size changed to value [200, 200] for button None
count is 1 and size is [200, 200]
count is 0 and size is [200, 200]
Size changed to value [100, 100] for button 0
init is being called and type is Lemon
Size changed to value [200, 200] for button None
count is 1 and size is [200, 200]
Size changed to value [100, 100] for button 1


I suspect that changing inventory_ingredient to an ObjectProperty would allow it to get updated on-the-fly, but I didn’t want all of the automatically generated event listeners that would come with that because it shouldn't change post-initialization. And obviously I can also force size=(200,200) every time I change data. But both those solutions feel like a shallow workaround because I’m brand new to Kivy and lack a fuller understanding of the behavior that’s happening.

PS In RV.__init__, I tried 1. setting self.data before calling super().__init__() and 2. passing super().__init__(data=data, **kwargs) but neither worked.

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