why userControl not update argument

[bobwatcherx]

Question

i make cuprttinoappbar and change page for render userControl . i change page and print i see number selected_index change and why my content not change

Code sample

from flet import *

class RenderPage(UserControl):
    def __init__(self, mycontent):
        super().__init__()
        self.mycontent = mycontent
    def build(self):
        return Column([
            Text(self.mycontent, size=30),
        ])


def main(page: Page):
    render_page = RenderPage(1)

    def change_page(e):
        if e.control.selected_index == 0 :
            render_page.mycontent = "home"
        if e.control.selected_index == 1 :
            render_page.mycontent = "2"
        else :
            render_page.mycontent = "3"
        page.update()

    page.navigation_bar = CupertinoNavigationBar(
        bgcolor="red",
        inactive_color="white",
        active_color="black",
        on_change=change_page,
        destinations=[
            NavigationDestination(icon=icons.HOME, label="Home"),
            NavigationDestination(icon=icons.SHOPPING_CART, label="Commute"),
            NavigationDestination(
                icon=icons.PERSON_2_ROUNDED,
                label="Settings",
            ),
        ]
    )
    page.add(
        Column([
            render_page
        ])
    )


app(target=main, view=AppView.WEB_BROWSER, port=5050)

Error message

No response

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• I have searched for answers to my question both in the issues and in previous discussions.