Google OAuth 2 - How to get refresh token using Xamarin.Auth?

Question

I'm using Xamarin.Auth to authenticate the user and have access to the Google Calendar API. I'm able to get an access token and do whatever I need. The problem is the access_token I receive expires after one hour. I looked for examples and information about this in several posts but I'm still not able to ask for new tokens. Here is the code I'm using in my Xamarin.Droid Project:

public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsApplicationActivity
{
    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        global::Xamarin.Forms.Forms.Init(this, bundle);
        LoadApplication(new App());

        #region [GoogleAuthentication]

        if (App.auth == null)
        {
            App.auth = new GoogleAuthenticator(App.WebApplicationClientID,
            new Uri("https://www.googleapis.com/plus/v1/people/me"),
            CalendarService.Scope.Calendar);
        }

        // We don't want to have to login every time, so we'll use the Xamarin.Auth AccountStore
        AccountStore store = AccountStore.Create(this);
        Account savedAccount = store.FindAccountsForService("google").FirstOrDefault();
        if (savedAccount != null)
        {
            App.auth.Account = savedAccount;
        }
        else
        {
            App.auth.Completed += (sender, args) =>
            {
                if (args.IsAuthenticated)
                {
                    // Save the account for the future
                    store.Save(args.Account, "google");
                }
            };

            Intent loginIntent = App.auth.GetUI(this);
            StartActivity(loginIntent);
        }

        #endregion [GoogleAuthentication]
    }

The GoogleAuthenticator class implements OAuth2Authenticator as seen below:

public class GoogleAuthenticator
    : OAuth2Authenticator
{
    public GoogleAuthenticator(string clientId, Uri callbackUri, params string[] scopes)
        : base(
            clientId,
            (scopes ?? Enumerable.Empty<string>()).Aggregate(string.Empty, (o, s) => o + " " + s),
            new Uri("https://accounts.google.com/o/oauth2/auth"),
            callbackUri,
            null)
    {
        Completed += (sender, args) =>
        {
            Account = args.Account;
        };
    }

    public Account Account
    {
        get;
        set;
    }

    public void ApplyAuthenticationToRequest(HttpWebRequest request)
    {
        if (Account == null)
            throw new InvalidOperationException("You must be authenticated to make requests");

        string token = Account.Properties["access_token"];
        string type = Account.Properties["token_type"];
        request.Headers[HttpRequestHeader.Authorization] = String.Format("{0} {1}", type, token);
    }
}

I tried changing the authorizationUrl adding the parameters approval_prompt=force and access_type=offline but it didn't work too.

How can I get the refresh_token using Xamarin.Auth?

Thanks.

I have no experience with it, but I think this link provides a great explanation about it: https://lostechies.com/jimmybogard/2014/11/13/mobile-authentication-with-xamarin-auth-and-refresh-tokens/ basically, the GetInitialUrlAsync method is overriden, a RequestRefreshTokenAsync method is created and called. Check if it works for you. — Luis Beltran, Apr 30 '16 at 08:59
Hi Luis, thanks. I saw this link but it didn't help me understanding the problem. — Daniel Kern, May 02 '16 at 04:24

score 1 · Answer 1 · edited May 23 '17 at 12:23

1

Have you seen this sample code here it looks like you can get the refresh Token from the account object you get back:

CurrentUser.Properties["refresh_token"]

current user is set here

so in you code it would just be:

Account.Properties["refresh_token"];

Also this question is similiar Xamarin.Auth with Google APIs: Renew credentials?

edited May 23 '17 at 12:23

Community

1
1

answered Apr 30 '16 at 09:40

Iain Smith

9,230
4
50
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Hi Iain. Thanks for your response and help. The problem is I never get a **refresh_token**. All answers and posts I saw about this issue assume I get a refresh_token. – Daniel Kern May 02 '16 at 04:22

score 0 · Answer 2 · answered Aug 24 '17 at 08:34

The documentation can be found here: https://developers.google.com/identity/protocols/OAuth2InstalledApp In the constructor of OAuth2Authenticator you pass in null as a accessTokenUrl. Therefore I guess your library cannot get past Step 5, the exchange of the authorization code for refresh and access tokens.

Google OAuth 2 - How to get refresh token using Xamarin.Auth?

2 Answers2