For our new friends:

Logto is an Auth0 alternative designed for modern apps and SaaS products. It offers both Cloud and Open-source services to help you quickly launch your identity and management (IAM) system. Enjoy authentication, authorization, and multi-tenant management all in one.

We recommend starting with a free development tenant on Logto Cloud. This allows you to explore all the features easily.

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

Prerequisites

• A running Logto instance. Check out the introduction page to get started.
• Basic knowledge of Android (Kotlin / Java).
• A usable Kakao account.

Create an application in Logto

Logto is based on OpenID Connect (OIDC) authentication and OAuth 2.0 authorization. It supports federated identity management across multiple applications, commonly called Single Sign-On (SSO).

To create your Native app application, simply follow these steps:

1. Open the Logto Console. In the "Get started" section, click the "View all" link to open the application frameworks list. Alternatively, you can navigate to Logto Console > Applications, and click the "Create application" button.
2. In the opening modal, click 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.
3. 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 Android (Kotlin) / Android (Java) 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
}

Configure redirect URI

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".

Implement sign-in and sign-out

note:

Before calling logtoClient.signIn, make sure you have correctly configured Redirect URI in Admin Console.

You can use logtoClient.signIn to sign in the user and logtoClient.signOut to sign out the user.

For example, in an Android app:

LogtoModelView.kt

//...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 call the signIn and signOut methods in your activity:

MainActivity.kt

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)
        }

        // Assume you have a button with id "sign_out_button" in your layout
        val signOutButton = findViewById<Button>(R.id.sign_out_button)
        signOutButton.setOnClickListener {
            if (logtoViewModel.authenticated) { // Check if the user is authenticated
                logtoViewModel.signOut()
            }
        }

        // Observe the authentication status to update the UI
        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
            }
        }

    }
}

Checkpoint: Test your application

Now, you can test your application:

1. Run your application, you will see the sign-in button.
2. Click the sign-in button, the SDK will init the sign-in process and redirect you to the Logto sign-in page.
3. After you signed in, you will be redirected back to your application and see the sign-out button.
4. Click the sign-out button to clear token storage and sign out.

Add Kakao connector

To enable quick sign-in and improve user conversion, connect with Android (Kotlin) / Android (Java) as an identity provider. The Logto social connector helps you establish this connection in minutes by allowing several parameter inputs.

To add a social connector, simply follow these steps:

1. Navigate to Console > Connectors > Social Connectors.
2. Click "Add social connector" and select "Kakao".
3. Follow the README guide and complete required fields and customize settings.

note:

If you are following the in-place Connector guide, you can skip the next section.

Set up Kakao login

Set up a project in the Kakao Devlopers Console

• Visit the Kakao Developers Console and sign in with your Kakao account.
• Click the Add an application to create new project or choose exist project.

Configure Kakao Login

Activate Kakao Login

• Click the Product Settings -> Kakao Login from the menu.
• Turn on Kakao Login Activation
• Add below URL into Redirect URI
  • http(s)://YOUR_URL/callback/${connector_id} (The connector_id can be found on the top bar of the Logto Admin Console connector details page.)
  • (Please replace YOUR_URL with your Logto URL, and choose http or https on your situation.)

Privacy Setting

• Click the Product Settings -> Kakao Login -> Consent Item from the menu.
• Change state of Nickname, Profile image, and Email to Required consent (You might not able to change Email to Required consent because of your project setting.)

Security Setting (Optional)

• Click the Product Settings -> Kakao Login -> Security from the menu.
• Click the Client secret code to generate secret code.
• Change Activation state to Enable. (If you enable it, secret code is necessary.)

Configure Logto

Config types

Name	Type
clientId	string
clientSecret	string?

clientId

clientId is REST API key of your project. (You can find it from summary of your project from Kakao developers console.)

clientSeceret

clientSecret is Secret Code of your project. (Please check Security Setting (Optional))

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 Kakao connector should be available now.

Enable Kakao connector in Sign-in Experience

Once you create a social connector successfully, you can enable it as a "Continue with Kakao" button in Sign-in Experience.

1. Navigate to Console > Sign-in experience > Sign-up and sign-in.
2. (Optional) Choose "Not applicable" for sign-up identifier if you need social login only.
3. Add configured Kakao connector to the "Social sign-in" section.

Testing and Validation

Return to your Android (Kotlin / Java) app. You should now be able to sign in with Kakao. Enjoy!

Further readings

End-user flows: Logto provides a out-of-the-box authentication flows including MFA and enterprise SSO, along with powerful APIs for flexible implementation of account settings, security verification, and multi-tenant experience.

Authorization: Authorization defines the actions a user can do or resources they can access after being authenticated. Explore how to protect your API for native and single-page applications and implement Role-based Access Control (RBAC).

Organizations: Particularly effective in multi-tenant SaaS and B2B apps, the organization feature enable tenant creation, member management, organization-level RBAC, and just-in-time-provisioning.

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