For our new friends:

Every app needs authentication and authorization. Logto is an Auth0 alternative designed for modern apps and SaaS products.

In this article, we will go through the steps to quickly build the Hugging Face sign-in experience (user authentication) with Android and  Logto.

Prerequisites

• A running Logto instance. Check out the introduction page to get started.
• Basic knowledge of Android.
• A usable Hugging Face account.

Create an application in Logto

In you browser, open a new tab and enter the link of Logto Admin Console.

Once the page is loaded, in the "Get Started" section click the View all link to open the application framework list page.

Choose your application type

In the opening modal, scroll to the "Native app" section or filter all the available " Native app" frameworks using the quick filter checkboxes on the left.

Click the "Android (Kotlin)" / "Android (Java)" framework card to start creating your application.

Enter application name

Enter the application name, e.g., "Bookstore," and click "Create application."

🎉 Ta-da! You just created your first application in Logto. You'll see a congrats page which includes a detailed integration guide. Follow the guide to see what the experience will be in your application.

Integrate Logto SDK

tip:

• The example is based on View system and View Model, but the concepts are the same when using Jetpack Compose.
• The example is written in Kotlin, but the concepts are the same for Java.
• Both Kotlin and Java sample projects are available on our SDK repository.
• The tutorial video is available on our YouTube channel.

Installation

note:

The minimum supported Android API level of Logto Android SDK is level 24.

Before you install Logto Android SDK, ensure mavenCentral() is added to your repository configuration in the Gradle project build file:

settings.gradle.kts

dependencyResolutionManagement {
  repositories {
    mavenCentral()
  }
}

Add Logto Android SDK to your dependencies:

Kotlin

build.gradle.kts

dependencies {
  implementation("io.logto.sdk:android:1.1.3")
}

Groovy

build.gradle

dependencies {
  implementation 'io.logto.sdk:android:1.1.3'
}

Since the SDK needs internet access, you need to add the following permission to your AndroidManifest.xml file:

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools">

  <!-- add internet permission -->
  <uses-permission android:name="android.permission.INTERNET" />

  <!-- other configurations... -->
</manifest>

Init LogtoClient

Create a LogtoViewModel.kt and init LogtoClient in this view model:

LogtoViewModel.kt

//...with other imports
import io.logto.sdk.android.LogtoClient
import io.logto.sdk.android.type.LogtoConfig

class LogtoViewModel(application: Application) : AndroidViewModel(application) {
    private val logtoConfig = LogtoConfig(
          endpoint = "<your-logto-endpoint>",
          appId = "<your-app-id>",
          scopes = null,
          resources = null,
          usingPersistStorage = true,
    )

    private val logtoClient = LogtoClient(logtoConfig, application)

    companion object {
        val Factory: ViewModelProvider.Factory = object : ViewModelProvider.Factory {
            @Suppress("UNCHECKED_CAST")
            override fun <T : ViewModel> create(
                modelClass: Class<T>,
                extras: CreationExtras
            ): T {
                // Get the Application object from extras
                val application = checkNotNull(extras[APPLICATION_KEY])
                return LogtoViewModel(application) as T
            }
        }
    }
}

then, create a LogtoViewModel for your MainActivity.kt:

MainActivity.kt

//...with other imports
class MainActivity : AppCompatActivity() {
    private val logtoViewModel: LogtoViewModel by viewModels { LogtoViewModel.Factory }
    //...other codes
}

Implement sign-in

Before starting, you need to add a redirect URI in the Admin Console for your application.

In Android, the redirect URI follows the pattern: $(LOGTO_REDIRECT_SCHEME)://$(YOUR_APP_PACKAGE)/callback:

• The LOGTO_REDIRECT_SCHEME should be a custom scheme in the reverse domain format.
• The YOUR_APP_PACKAGE is your app package name.

Assuming you treat io.logto.android as the custom LOGTO_REDIRECT_SCHEME, and io.logto.sample is your app package name, the Redirect URI should be io.logto.android://io.logto.sample/callback.

Let's switch to the Application details page of Logto Console. Add a Redirect URI io.logto.android://io.logto.sample/callback and click "Save changes".

After the redirect URI is configured, we add a signIn method to your LogtoViewModel.kt, which will call logtoClient.signIn API to invoke the Logto sign-in page:

//...with other imports
class LogtoViewModel(application: Application) : AndroidViewModel(application) {
    // ...other codes
    fun signIn(context: Activity) {
        logtoClient.signIn(context, "io.logto.android://io.logto.sample/callback") { logtoException ->
            logtoException?.let { println(it) }
        }
    }
}

Now setup on-click listener for the sign-in button in your MainActivity.kt to call the signIn method:

//...with other imports
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        //...other codes

        // Assume you have a button with id `sign_in_button` in your layout
        val signInButton = findViewById<Button>(R.id.sign_in_button)
        signInButton.setOnClickListener {
            logtoViewModel.signIn(this)
        }
    }
}

When you click the button, the Logto SDK will navigate to the Logto sign-in page.

Implement sign-out

Similar to sign-in, we add a signOut method to LogtoViewModel.kt to call logtoClient.signOut API:

//...with other imports
class LogtoViewModel(application: Application) : AndroidViewModel(application) {
    // ...other codes
    fun signOut() {
        logtoClient.signOut { logtoException ->
            logtoException?.let { println(it) }
        }
    }
}

After you signed out, the Logto SDK will clear all local credentials even though Logto exceptions occurred when calling logtoClient.signOut API.

Then, we can add a button to call the signOut method in MainActivity.kt:

//...with other imports
class MainActivity : AppCompatActivity() {
    //...other codes
    override fun onCreate(savedInstanceState: Bundle?) {
        //...other codes
        //...sign-in button codes

        // Assume you have a button with id `sign_out_button` in your layout
        val signOutButton = findViewById<Button>(R.id.sign_out_button)
        signOutButton.setOnClickListener {
            logtoViewModel.signOut()
        }
    }
}

Handle authentication status

In Logto SDK, we can use logtoClient.isAuthenticated to check the authentication status, if the user is signed in, the value will be true, otherwise, the value will be false.

Now, let's add a live data to LogtoViewModel.kt to observe the authentication status, and update the status when the user signed in or signed out:

//...with other imports
class LogtoViewModel(application: Application) : AndroidViewModel(application) {
    // ...other codes

    // Add a live data to observe the authentication status
    private val _authenticated = MutableLiveData(logtoClient.isAuthenticated)
    val authenticated: LiveData<Boolean>
        get() = _authenticated

    fun signIn(context: Activity) {
        logtoClient.signIn(context, "io.logto.android://io.logto.sample/callback") { logtoException ->
            logtoException?.let { println(it) }
            // Update the live data
            _authenticated.postValue(logtoClient.isAuthenticated)
        }
    }

    fun signOut() {
        logtoClient.signOut { logtoException ->
            logtoException?.let { println(it) }
            // Update the live data
            _authenticated.postValue(logtoClient.isAuthenticated)
        }
    }
}

Then, we observe the authenticated live data in MainActivity.kt, when the user is signed in, we hide the sign-in button and show the sign-out button and vice versa:

//...with other imports
class MainActivity : AppCompatActivity() {
    //...other codes
    override fun onCreate(savedInstanceState: Bundle?) {
        //...other codes
        val signInButton = findViewById<Button>(R.id.sign_in_button)
        val signOutButton = findViewById<Button>(R.id.sign_out_button)
        // ...handle button click codes

        // Observe the authentication status
        logtoViewModel.authenticated.observe(this) { authenticated ->
            if (authenticated) {
                // The user is authenticated
                signInButton.visibility = View.GONE
                signOutButton.visibility = View.VISIBLE
            } else {
                // The user is not authenticated
                signInButton.visibility = View.VISIBLE
                signOutButton.visibility = View.GONE
            }
        }
    }
}

Test your integration:

Open your Android app to test if the integration works. When you click the "Sign In" button, the page should be redirected to a Logto sign-in page, and you should be able to create a new account by entering username and password and complete the sign-in process.

Add Hugging Face connector

To add a social connector, go to the "Connector" tab in the Admin Console, then click on "Social connectors". From there, click "Add social connector".

In the openning modal, select "Hugging Face" and click "Next".

On the next page, you will see a two-column layout with the README content on the left and configuration on the right.

Feel free to follow the README file in place or read the following section to complete the configuration process. If you follow the in-place guide, you can skip the next section.

Set up Hugging Face OAuth app

Sign in with Hugging Face account

Go to the Hugging Face website and sign in with your Hugging Face account. You may register a new account if you don't have one.

Create an OAuth app in the Hugging Face

Follow the Creating an oauth app guide, and register a new application.

In the creation process, you will need to provide the following information:

• Application Name: The name of your application.
• Homepage URL: The URL of your application's homepage or landing page.
• Logo URL: The URL of your application's logo.
• Scopes: The scopes allowed for the OAuth app. For Hugging Face connector, usually use profile to get the user's profile information and email to get the user's email address. Ensure these scopes are allowed in your Hugging Face OAuth app if you want to use them.
• Redirect URI: The URL to redirect the user to after they have authenticated. You can find the redirect URI in the Logto Admin Console when you're creating a Hugging Face connector or in the created Hugging Face connector details page.

Managing Hugging Face OAuth apps

Go to the Connected Applications page, you can add, edit or delete existing OAuth apps. You can also find Client ID and generate App secrets in corresponding OAuth app settings pages.

Configure your connector

Go back to Logto Admin Console And Fill out the clientId and clientSecret field with Client ID and App Secret you've got from OAuth app detail pages mentioned in the previous section.

scope is a space-delimited list of Hugging Face supported scopes. If not provided, scope defaults to be profile. For Hugging Face connector, the scope you may want to use is profile and email. profile scope is required to get the user's profile information, and email scope is required to get the user's email address. Ensure you have allowed these scopes in your Hugging Face OAuth app (configured in Create an OAuth app in the Hugging Face section).

Config types

Name	Type
clientId	string
clientSecret	string
scope	string

Save your configuration

Double check you have filled out necessary values in the Logto connector configuration area. Click "Save and Done" (or "Save changes") and the Hugging Face connector should be available now.

Enable Hugging Face connector in Sign-in Experience

Switch to the "Sign-in experience" tab, then click the "Sign-up and sign-in" tab.

note:

If it's the first time you enter the tab, you will see a quick introduction about Sign-in Experience and its basic configuration.

Select "None" for the "Sign-up identifier" to provide minimum sign-up effort for Hugging Face sign-in, which may increase your conversion rate.

In the "Social sign-in" section, add "Add Social Connector" and choose "Hugging Face". Then you should be able to see a button with text "Continue with Hugging Face" in the preview section.

Finally, click "Save changes" on the bottom right corner.

Testing and Validation

Return to your Android app. You should now be able to sign in with Hugging Face. Enjoy!

Further readings

Protect your API For native and single page apps, you'll need to call one or more API endpoints to retrieve and update data.
Learn more about identifying who's who and keeping your API secure.

User management We know you care about user management and activities, as we also do.
Learn more about how to know your users and see the figures like DAU and MAU graphically.

Localization From one regional business to a global corporate, the willingness to offer the best user experience won't change.
You can change current language phrases or add a new language without friction.

Customer IAM series Our serial blog posts about Customer (or Consumer) Identity and Access Management, from 101 to advanced topics and beyond.