Xamarin SDK

How to integrate with a Xamarin app

This guide provides instructions on integrating Authgear with a Xamarin app. Supported packages include:

• Xamarin.Essentials 1.7.2 or higher

• Xamarin.Forms 5.0.0.2401 or higher

Setup Application in Authgear

Signup for an Authgear Portal account in https://portal.authgear.com/. Or you can use your self-deployed Authgear.

From the Project listing, create a new Project or select an existing Project. After that, we will need to create an application in the project.

Portal

Step 1: Create an application in the Portal

1. Go to Applications on the left menu bar.

2. Click ⊕Add Application in the top tool bar.

3. Input the name of your application and select Native App as the application type. Click "Save".

4. You will see a list of guides that can help you for setting up, then click "Next".

Create an application

Step 2: Configure the application

1. In your IDE (e.g. Visual Studio), define a custom URI scheme that the users will be redirected back to your app after they have authenticated with Authgear, e.g. com.myapp.example://host/path.[^1]

2. Head back to Authgear Portal, fill in the Redirect URI that you have defined in the previous steps.

3. Click "Save" in the top tool bar and keep the Client ID. You can also obtain it again from the Applications list later.

Edit an application

If you wish to validate JSON Web Token (JWT) in your own application server, turn on "Issue JWT as access token".[^2] If you wish to forward authentication requests to Authgear Resolver Endpoint, leave this unchecked. See comparisons in Backend Integration.

authgear.yaml (self-deployed)

oauth:
  clients:
    - name: your_app_name
      client_id: a_random_generated_string
      redirect_uris:
        - "com.myapp.example://host/path"
      grant_types:
        - authorization_code
        - refresh_token
      response_types:
        - code
        - none

Create a Xamarin app

• Open Visual Studio

• Create a new project

• Choose the Xamarin.Forms template

Install the SDK

• Search for "Authgear.Xamarin" on nuget.org and add it to your base project. https://www.nuget.org/packages/Authgear.Xamarin/

• Authgear.Xamarin targets MonoAndroid 12.0 on Android, and Xamarin.iOS10 on iOS. Update the target framework of the Android and iOS projects to match Authgear.Xamarin's target frameworks.

• Update Android and iOS project's Xamarin.Essentials to 1.7.2.

Platform Integration

To finish the integration, setup the app to handle the redirectURI specified in the application. This part requires platform specific integration.

Android

Define your own callback activity

using System;

using Android.App;
using Android.Content.PM;
using Android.Runtime;
using Android.OS;
using Authgear.Xamarin;
using Xamarin.Forms;

namespace MyApp.Droid
{
    [Activity(NoHistory = true, LaunchMode = LaunchMode.SingleTop, Exported = true)]
    [IntentFilter(new[] { Android.Content.Intent.ActionView },
        Categories = new[] { Android.Content.Intent.CategoryDefault, Android.Content.Intent.CategoryBrowsable },
        DataScheme = "com.myapp.example")]
    public class WebAuthenticationCallbackActivity : Xamarin.Essentials.WebAuthenticatorCallbackActivity
    {
    }
}

Targeting API level 30 or above (Android 11 or above)

If your Android app is targeting API level 30 or above (Android 11 or above), you need to add a queries section to AndroidManifest.xml.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
  <!-- Other elements such <application> -->
  <queries>
    <intent>
      <action android:name="android.support.customtabs.action.CustomTabsService" />
    </intent>
  </queries>
</manifest>

Initialize a global AuthgearSdk instance

In your MainActivity.cs

using System;

using Android.App;
using Android.Content.PM;
using Android.Runtime;
using Android.OS;

using Xamarin.Forms;
using Authgear.Xamarin;

namespace MyApp.Droid
{
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            // ...

            var authgear = new AuthgearSdk(this, new AuthgearOptions
            {
                ClientId = CLIENT_ID,
                AuthgearEndpoint = ENDPOINT
            });
            DependencyService.RegisterSingleton<AuthgearSdk>(authgear);
            LoadApplication(new App());

            // ...
        }

        // other methods are omitted for brevity.
    }
}

iOS

Add the following key-value pair in your iOS project Info.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <!-- other entries ... -->
        <key>CFBundleURLTypes</key>
        <array>
          <dict>
            <key>CFBundleURLName</key>
            <string>com.myapp.example://host/path</string>

            <key>CFBundleURLSchemes</key>
            <array>
              <string>com.myapp.example</string>
            </array>

            <key>CFBundleTypeRole</key>
            <string>Editor</string>
          </dict>
        </array>
</dict>
</plist>

Initialize a global AuthgearSdk instance

In your AppDelegate.cs

using Xamarin.Essentials;
using Xamarin.Forms;
using Authgear.Xamarin;

namespace MyApp.iOS
{
    [Register("AppDelegate")]
    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
    {
        public override bool FinishedLaunching(UIApplication app, NSDictionary options)
        {
            global::Xamarin.Forms.Forms.Init();
            var authgear = new AuthgearSdk(app, new AuthgearOptions
            {
                ClientId = CLIENT_ID,
                AuthgearEndpoint = ENDPOINT
            });
            DependencyService.RegisterSingleton<AuthgearSdk>(authgear);
            LoadApplication(new App());

            return base.FinishedLaunching(app, options);
        }

        public override bool OpenUrl(UIApplication app, NSUrl url, NSDictionary options)
        {
            return Xamarin.Essentials.Platform.OpenUrl(app, url, options);
        }

        public override bool ContinueUserActivity(UIApplication application, NSUserActivity userActivity, UIApplicationRestorationHandler completionHandler)
        {
            if (Xamarin.Essentials.Platform.ContinueUserActivity(application, userActivity, completionHandler))
                return true;
            return base.ContinueUserActivity(application, userActivity, completionHandler);
        }
    }
}

Try authenticate

Edit your MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="testauthgear.MainPage">

    <StackLayout>
        <Frame BackgroundColor="#2196F3" Padding="24" CornerRadius="0">
            <Label Text="Welcome to Xamarin.Forms!" HorizontalTextAlignment="Center" TextColor="White" FontSize="36"/>
        </Frame>
        <Button Text="Configure" Clicked="Configure_Clicked" />
        <Button Text="Authenticate" Clicked="Authenticate_Clicked"/>
    </StackLayout>

</ContentPage>

Edit your MainPage.xaml.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using Authgear.Xamarin;

namespace MyApp
{
    public partial class MainPage : ContentPage
    {
        private AuthgearSdk authgear;


        public MainPage()
        {
            InitializeComponent();
            authgear = DependencyService.Get<AuthgearSdk>();
        }

        async void Configure_Clicked(object sender, EventArgs e)
        {
            // You must configure the instance before use.
            // Typically you should do this once on app launch.
            await authgear.ConfigureAsync();
        }

        async void Authenticate_Clicked(object sender, EventArgs e)
        {
            var userInfo = await authgear.AuthenticateAsync(new AuthenticateOptions
            {
                RedirectUri = REDIRECT_URI
            });
        }
    }
}

Get the Logged In State

When you start launching the application. You may want to know if the user has logged in. (e.g. Show users the login page if they haven't logged in). The SessionState reflects the user logged in state in the SDK locally on the device. That means even the SessionState is Authenticated, the session may be invalid if it is revoked remotely. After initializing the Authgear SDK, call FetchUserInfoAsync to update the SessionState as soon as it is proper to do so.

// value can be NoSession or Authenticated
// After Authgear.ConfigureAsync, it only reflects local state.
var sessionState = authgear.SessionState;

if (sessionState == SessionState.Authenticated)
{
    try
    {
        var userInfo = await authgear.FetchUserInfoAsync();
        // sessionState is now up to date
    }
    catch (Exception ex)
    {
        // sessionState is now up to date
        // it will change to NoSession if the session is invalid
    }
}

The value of SessionState can be Unknown, NoSession or Authenticated. Initially, the SessionState is Unknown. After a call to authgear.configure, the session state would become Authenticated if a previous session was found, or NoSession if such session was not found.

Fetching User Info

In some cases, you may need to obtain current user info through the SDK. (e.g. Display email address in the UI). Use the FetchUserInfoAsync function to obtain the user info, see example.

Logout

To log out the user from the current app session, you need to invoke thelogoutfunction.

await authgear.LogoutAsync();

Calling An API

To include the access token to the HTTP requests to your application server, you set the bearer token manually by using authgear.AccessToken.

Using HttpClient

You can get the access token through authgear.AccessToken. Call RefreshAccessTokenIfNeededAsync every time before using the access token, the function will check and make the network call only if the access token has expired. Then, include the access token into the Authorization header of the http request.

await authgear.RefreshAccessTokenIfNeededAsync();
// Access token is ready to use
// AccessToken can be string or undefined
// It will be empty if user is not logged in or session is invalid
var accessToken = authgear.AccessToken;
var client = GetHttpClient();  // Get the re-used http client of your app, as per recommendation.
var httpRequestMessage = new HttpRequestMessage(myHttpMethod, myUrl);
httpRequestMessage.Headers.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);

Next steps

To protect your application server from unauthorized access. You will need to integrate your backend with Authgear.

pageBackend Integration

Xamarin SDK Reference

For detailed documentation on the Xamarin SDK, visit Xamarin SDK Reference

Footnote

[^1]: For futher instruction on setting up custom URI scheme in Xamarin, see https://www.xamarinhelp.com/uri-scheme/ [^2]: For more explaination on JWT, see https://en.wikipedia.org/wiki/JSON_Web_Token