How to properly use SharedPreferences after ClientStorage removal in Flet 0.80.0?

[gt-diego-pizarro]

Question

Hi everyone 👋

I’m looking for some guidance after upgrading my project to Flet v0.80.0.

I have a Flet app that uses Auth0 for authentication and stores the user token persistently using SharedPreferences. Before the upgrade, I was using ClientStorage, but after updating Flet I had to migrate everything to SharedPreferences, and that’s where my logic started to break.

Now I’m getting errors like this when trying to save the token:

RuntimeError: SharedPreferences(26) Control must be added to the page first

From what I understand, SharedPreferences is now treated as a control that must be attached to the page, but I’m not fully sure what the correct or recommended pattern is to manage it across my app.

My questions are:

• How should SharedPreferences be properly initialized and attached to the page?
• Is it meant to be created once (for example in main(page)) and then passed around?
• What’s the cleanest way to access it from services or async functions like my auth_service without tightly coupling everything to the page?

If anyone has a working example or can point me to the right pattern after the ClientStorage → SharedPreferences migration, I’d really appreciate it 🙏

Thanks in advance!

Code sample

main.py

import flet as ft
import logging

from utils.settings import settings
from services.auth_service import AuthService
from layout.layout import load_main_app_layout
from screens.login_screen import LoginScreen
from utils.logger import setup_logging, get_logger


setup_logging(level=logging.INFO)
logger = get_logger('main')


async def main(page: ft.Page):
    page.theme_mode = settings.theme_mode
    # page.adaptive = True
    auth = AuthService(page)

    def on_login_success():
        page.controls.clear()
        load_main_app_layout(page, auth)

    def on_logout_success():
        page.controls.clear()
        page.appbar = None
        page.navigation_bar = None
        login_screen = LoginScreen(auth)
        page.add(login_screen)
        page.update()

    auth.set_login_handler(on_login_success)
    auth.set_logout_handler(on_logout_success)

    if not await auth.user_is_authenticated():
        page.appbar = None
        page.navigation_bar = None
        login_screen = LoginScreen(auth)
        page.add(login_screen)
    else:
        load_main_app_layout(page, auth)


ft.run(main, port=8550, view=ft.AppView.WEB_BROWSER)
# ft.app(main, view=ft.AppView.WEB_BROWSER)

---

auth_service.py

import os
import base64
import hashlib
import secrets
import flet as ft

from dotenv import load_dotenv
from flet.auth import OAuthProvider
from flet.security import decrypt, encrypt
from utils.logger import get_logger

logger = get_logger('services.auth')
load_dotenv()

MY_APP_SECRET_KEY = os.getenv("MY_APP_SECRET_KEY")
AUTH0_CLIENT_ID = os.getenv("AUTH0_CLIENT_ID")
AUTH0_DOMAIN = os.getenv("AUTH0_DOMAIN")
APP_ENV = os.getenv("APP_ENV", "development")



class AuthService:
    def __init__(self, page):
        self.page = page
        self.secret_key = MY_APP_SECRET_KEY
        self.token_key = "auth0_token"
        self.provider, self.logout_url = self._setup_provider()

    def _generate_pkce_pair(self):
        code_verifier = base64.urlsafe_b64encode(secrets.token_bytes(32)).rstrip(b"=").decode("utf-8")
        code_challenge = base64.urlsafe_b64encode(
            hashlib.sha256(code_verifier.encode()).digest()
        ).rstrip(b"=").decode("utf-8")
        return code_verifier, code_challenge

    def _setup_provider(self):
        if APP_ENV == "local":
            sufix = ""
            is_mobile = self.page.platform in (
                ft.PagePlatform.IOS,
                ft.PagePlatform.ANDROID
            )
            sufix = "_TEST_IOS" if is_mobile else "_DESKTOP"
            redirect_url = os.getenv(f"AUTH0_CALLBACK_URL{sufix}")
            return_to_url = os.getenv(f"RETURN_TO_URL{sufix}")
        else:
            # redirect_url = os.getenv("AUTH0_CALLBACK_URL")
            # return_to_url = os.getenv("RETURN_TO_URL")
            redirect_url = "myapp://oauth_callback"
            return_to_url = "myapp://oauth_callback"

        logout_url = (
            f"https://{AUTH0_DOMAIN}/v2/logout"
            f"?client_id={AUTH0_CLIENT_ID}"
            f"&returnTo={return_to_url}"
        )

        provider = OAuthProvider(
            client_id=AUTH0_CLIENT_ID,
            client_secret="",
            redirect_url=redirect_url,
            authorization_endpoint=f"https://{AUTH0_DOMAIN}/authorize",
            token_endpoint=f"https://{AUTH0_DOMAIN}/oauth/token",
            user_endpoint=f"https://{AUTH0_DOMAIN}/userinfo",
            user_id_fn=lambda u: u.get("sub"),
            scopes=["openid", "profile", "email"],
        )
        return provider, logout_url

    async def get_saved_token(self):
        # Flet 0.80.0: shared_preferences es asíncrono, usar await
        ejt = await ft.SharedPreferences().get(self.token_key)
        return decrypt(ejt, self.secret_key) if ejt else None

    async def save_token(self, token_json):
        ejt = encrypt(token_json, self.secret_key)
        save = await ft.SharedPreferences().set(self.token_key, ejt)
        if save:
            print("Token saved successfully")

    async def clear_token(self):
        await ft.SharedPreferences().remove(self.token_key)

    async def perform_login(self, complete_page_html):
        saved_token = await self.get_saved_token()
        await self.page.login(
            self.provider,
            saved_token=saved_token,
            complete_page_html=complete_page_html,
        )

    async def perform_logout(self):
        await self.clear_token()
        await self.page.logout_async()
        if APP_ENV == "local":
            self.page.launch_url(self.logout_url)

    async def user_is_authenticated(self):
        ejt = await ft.SharedPreferences().get(self.token_key)
        return ejt is not None

    def get_logged_user_name(self):
        if self.page.auth and self.page.auth.user:
            return self.page.auth.user.get("name", self.page.auth.user.get("email", "User"))
        return "No autenticado"

    def set_login_handler(self, on_login_success):
        async def on_login(e: ft.LoginEvent):
            if e.error:
                raise Exception(e.error)
            token = await self.page.auth.get_token()
            if token:
                await self.save_token(token.to_json())
            print("Login successful")
            on_login_success()
        self.page.on_login = on_login

    def set_logout_handler(self, on_logout_success):
        async def on_logout(e):
            await self.perform_logout()
            on_logout_success()
        self.page.on_logout = on_logout

Error message

Traceback (most recent call last):
  File "/XXXX/auth_service.py", line 118, in on_login
    await self.save_token(token.to_json())
  File "/XXXX/auth_service.py", line 82, in save_token
    save = await ft.SharedPreferences().set(self.token_key, ejt)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/XXXX/Library/Caches/pypoetry/virtualenvs/first-flet-app-9bug_W48-py3.14/lib/python3.14/site-packages/flet/controls/services/shared_preferences.py", line 21, in set
    return await self._invoke_method("set", {"key": key, "value": value})
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/XXXX/Library/Caches/pypoetry/virtualenvs/first-flet-app-9bug_W48-py3.14/lib/python3.14/site-packages/flet/controls/base_control.py", line 266, in _invoke_method
    if not self.page:
           ^^^^^^^^^
  File "/XXXX/Library/Caches/pypoetry/virtualenvs/first-flet-app-9bug_W48-py3.14/lib/python3.14/site-packages/flet/controls/base_control.py", line 201, in page
    raise RuntimeError(
    ...<2 lines>...
    )
RuntimeError: SharedPreferences(26) Control must be added to the page first

------------------------------------------------------

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

[ndonkoHenri]

See docs example: https://docs.flet.dev/services/sharedpreferences/

[ser]

Do you really store OpenID client_secret on your device for everyone to see?

[FeodorFitsner]

For safe OAuth login on device with either need to support device flow or/and add support for "proxy" app with auth flow and "localhost" callback web server on the client.

[FeodorFitsner]

There is indeed an issue with using SharedPreferences in on_login handler. Looking into this.

[FeodorFitsner]

@gt-diego-pizarro subscribe to #5996 with OAuth fix and updated examples

[gt-diego-pizarro]

Hi @FeodorFitsner!

Thanks a lot for the previous help — I managed to fix the SharedPreferences initialization issue following your guidance

I’m now running into a different problem and I’d like to ask for help again in the same thread, since it’s still related to my auth flow.

I’m trying to implement a login flow using a custom OAuthProvider, which internally uses Auth0 with PKCE. When I test this on an iOS emulator using:

flet debug ios

The app crashes during login with the following error:

File "flet/controls/page.py", line 695, in login
  self.session.connection.oauth_authorize(auth_attrs)
File "flet/messaging/connection.py", line 57, in oauth_authorize
  raise NotImplementedError()

From the logs, it looks like page.login() eventually calls oauth_authorize, but this method is not implemented for this platform/runtime.

My questions are:

Is page.login() with a custom OAuthProvider currently supported on iOS?

Is this a known limitation of Flet mobile (Flutter) targets?

Is there a recommended workaround for OAuth + PKCE on iOS?

Or am I missing some required configuration for mobile targets?

Thanks again for all the help! 🙌

[FeodorFitsner]

PKCE is not yet supported in Flet, but let me look into that: #6029