[Question] How to stop a button on_click callback progress?

[alxbz2]

Question

Sorry to bother, i am not an experienced python coder but this question really needs your help....
The question is how to stop a callback function which is in progressing by clicking another button? Because once a tesing progress triggered by one button and it will cost a lot of time to finnish, thus, i want to find out how to stop this progress by clicking another button? This maybe can solved by tricks like threading, async/await or something, but i just not get it..
Thank all of u for helping me to solve this problem.

Code sample

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Error message

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

[alxbz2]

I got some tips in https://flet.dev/docs/guides/python/async-apps/#getting-started-with-async
it worked with 'will_unmount_async' to stop a progress if we set a break flag in a loop; and 'did_mount_async' is not really required if we need a progress which is required to start with a certain event comes. And a modified test code is presented as followed,
However, i am still not understand how async/await works... = =..

import asyncio
import flet as ft


class Countdown(ft.UserControl):

    def __init__(self, seconds):
        super().__init__()
        self.seconds = seconds

    async def start_sync(self, e):
        self.running = True
        asyncio.create_task(self.update_timer())

    async def will_unmount_async(self, e):
        self.running = False

    async def update_timer(self):
        while self.seconds and self.running:
            mins, secs = divmod(self.seconds, 60)
            self.countdown.value = "{:02d}:{:02d}".format(mins, secs)
            await self.update_async()
            await asyncio.sleep(1)
            self.seconds -= 1

    def build(self):
        self.countdown = ft.Text()
        but = ft.ElevatedButton(text='stop', on_click=self.will_unmount_async)
        but2 = ft.ElevatedButton(text='start', on_click=self.start_sync)

        return ft.Row([self.countdown, but, but2])


async def main(page: ft.Page):
    a = Countdown(120)
    b = Countdown(60)
    await page.add_async(a, b)


ft.app(target=main)