Kivy: cant get scroll_to in Scrollview working

Question

Trying code like this I get the Scrollview to work nicely but the scroll_to() function doesn't do anything. The view still starts at the top position.

pixperhour = 60
tagHL = []

dayview = ScrollView(size_hint=(1,1))
test = BoxLayout(size_hint=(1,None), height=24*pixperhour, orientation='vertical')
dayview.add_widget(test)

for i in range(24):
    tagHL.append(Label())
    test.add_widget(tagHL[i])
    tagHL[i].text = "Label "+str(i)
    tagHL[i].color = (1, 1, 1)
    tagHL[i].font_size = 30

dayview.scroll_to(tagHL[12])

I would expect the viewport of the scrollview to change so that the label tagHL[12] becomes visible. Am I doing it wrong or is the function bugged?

Answer 1

In order to make it happen as soon as the widget creation is done you can schedule it after (or, before) some (or, no) time as, Clock.schedule_once(lambda *args : dayview.scroll_to(tagHL[12]),dt) where dt can be -1, 0 or any positive value.

As a side note, if you are using tagHL just as a widget container then it will better to use the children attribute of the BoxLayout, test. So, that will be like,

    for i in range(24):
        self.lbl = Label(
            text=f"Label {i}",
            color = [1, 1, 1],
            font_size = 30,
        )
        test.add_widget(self.lbl)
    Clock.schedule_once(lambda *x : dayview.scroll_to(test.children[::-1][12]))