如何保留 Firebase Auth 并在以后使用它登录？

Question

I want the feature in my app, that a user can login with multiple accounts and switch between these accounts without having to enter the email and password again.

One obvious approach that works is to persist the email-password-pairs. But that is highly insecure.

So instead I would prefer to persist the session / token of that account. And when switching the account, we logout from that account, get the session / token from the other account and use that to login. Unfortunately I just cannot find where to get that session / token. AFAIK Firebase does what I described above internally (they persist the session / token to the SharedPreferences, and use that to authenticate the user on app start).

So how can I do that myself? (My platform is Android)

Answer 1

From the documentation on Authenticate with Firebase Using a Custom Authentication System

You can integrate Firebase Authentication with a custom authentication system by modifying your authentication server to produce custom signed tokens when a user successfully signs in. Your app receives this token and uses it to authenticate with Firebase.

When users sign in to your app, send their sign-in credentials (for example, their username and password) to your authentication server. Your server checks the credentials and returns a custom token if they are valid.Refer this document on create custom tokens

After you receive the custom token from your authentication server, pass it to signInWithCustomToken to sign in the user:

 import { getAuth, signInWithCustomToken } from "firebase/auth"; const auth = getAuth(); signInWithCustomToken(auth, token).then((userCredential) => { // Signed in const user = userCredential.user; //... }).catch((error) => { const errorCode = error.code; const errorMessage = error.message; //... });

You can also check this stackoverflow thread