Obtain a new token by refresh token with google_sign_in Flutter - flutter

Question

I'm writing an application that call google fit rest api from Flutter.
I need to sign with google using (https://pub.dev/packages/google_sign_in).
I can obtain a token without problem (see Did anyone manage to get the id token from google sign in (Flutter)) but how to obtain a new token when it is expired?
I dont' want to ask to the user to login and obtain a new token every hour

Answer 1

You can do this in 2 ways.
You can use the API.
I don't know if this is standard but you can do a silent login every time the user opens the app, the silent log logs into the user account without user interaction and this way you have a new token. Like this:
Future<String> refreshToken() async {
print("Token Refresh");
final GoogleSignInAccount googleSignInAccount =
await googleSignIn.signInSilently();
final GoogleSignInAuthentication googleSignInAuthentication =
await googleSignInAccount.authentication;
final AuthCredential credential = GoogleAuthProvider.getCredential(
accessToken: googleSignInAuthentication.accessToken,
idToken: googleSignInAuthentication.idToken,
);
final AuthResult authResult = await auth.signInWithCredential(credential);
return googleSignInAuthentication.accessToken; // New refreshed token
}

Answer 2

Get refresh token manually
apiKey - your api key from firebase,
idToken - unexpired id token,
provider - 'google.com', 'apple.com' etc
final url = Uri.parse('https://identitytoolkit.googleapis.com/v1/accounts:signInWithIdp?key=$apiKey');
final response = await http.post(
url,
headers: {'Content-type': 'application/json'},
body: jsonEncode({
'postBody': 'id_token=$token&providerId=$provider',
'requestUri': 'http://localhost',
'returnIdpCredential': true,
'returnSecureToken': true
})
);
if (response.statusCode != 200) {
throw 'Refresh token request failed: ${response.statusCode}';
}
final data = Map<String, dynamic>.of(jsonDecode(response.body));
if (data.containsKey('refreshToken')) {
// here is your refresh token, store it in a secure way
} else {
throw 'No refresh token in response';
}

Answer 3

Before calling '.signIn()' method make sure that GoogleSignInAccount variable type has 'forceCodeForRefreshToken' set up with true.
After that take 'serverAuthCode' and make a request to https://accounts.google.com/o/oauth2/token with the next body
'access_type': 'offline', tokenType: <serverAuthCode>, 'grant_type': 'code', 'client_secret': <yourClientSecret>, 'client_id': <yourClientId>, 'redirect_uri': <yourMiddleWare>,.
In response you will get that refresh_token.