Updated gist to use default back button

routes.py

import flet
from flet import AppBar
from flet import ElevatedButton
from flet import Page
from flet import Text
from flet import View


class FirstPage(View):
    def __init__(self, page):
        super().__init__(
            '/',
            [
                AppBar(title=Text("Flet app")),
                ElevatedButton("Go to settings", on_click=self.open_settings),
            ]
        )

        self.page = page

    def open_settings(self, e):
        self.page.views.append(
            View(
                "/settings",
                [
                    AppBar(title=Text("Settings")),
                    Text("Settings"),
                ],
            )
        )
        self.page.update()


def default_view_pop(view):
    page = view.page
    page.views.pop()
    page.update()


def main(page: Page):
    page.title = "Routes Example"
    page.views.clear()
    page.views.append(FirstPage(page))
    page.on_view_pop = default_view_pop
    page.update()


flet.app(target=main)