A callback URL is a URL in your application where Auth0 redirects the user after they have authenticated.

You need to whitelist the callback URL for your app in the Allowed Callback URLs field in your Application Settings. If you do not set any callback URL, your users will see a mismatch error when they log in.

Add the Auth0 Android SDK into your project. The library makes requests to the Auth0's Authentication and Management APIs.

In your app's build.gradle dependencies section, add the following:

apply plugin: 'com.android.application'
android {
  //..
}
dependencies {
  //---> Add the next line
  implementation 'com.auth0.android:auth0:1.+'
  //<---
}

Add manifest placeholders required by the SDK. The placeholders are used internally to define an intent-filter that captures the authentication callback URL.

To add the manifest placeholders, add the next line:

apply plugin: 'com.android.application'
android {
    compileSdkVersion 25
    buildToolsVersion "25.0.3"
    defaultConfig {
        applicationId "com.auth0.samples"
        minSdkVersion 15
        targetSdkVersion 25
        //...

        //---> Add the next line
        manifestPlaceholders = [auth0Domain: "@string/com_auth0_domain", auth0Scheme: "demo"]
        //<---
    }
}

Run Sync Project with Gradle Files inside Android Studio or execute ./gradlew clean assembleDebug from the command line.

Universal Login is the easiest way to set up authentication in your application. We recommend using it for the best experience, best security and the fullest array of features.

In the login method, create a new instance of the Auth0 class to hold user credentials.

You can use a constructor that receives an Android Context if you have added the following String resources:

• R.string.com_auth0_client_id
• R.string.com_auth0_domain

If you prefer to hardcode the resources, use the constructor that receives both strings. Then, use the WebAuthProvider class to authenticate with any connection you enabled on your application in the Auth0 dashboard.

After you call the WebAuthProvider#start function, the browser launches and shows the Lock widget. Once the user authenticates, the callback URL is called. The callback URL contains the final result of the authentication process.

// app/src/main/java/com/auth0/samples/MainActivity.java

private void login() {
    WebAuthProvider.init(auth0)
        .withScheme("demo")
        .withAudience(String.format("https://%s/userinfo", getString(R.string.com_auth0_domain)))
        .start(MainActivity.this, new AuthCallback() {
            @Override
            public void onFailure(@NonNull Dialog dialog) {
               // Show error Dialog to user
            }

            @Override
            public void onFailure(AuthenticationException exception) {
               // Show error to user
            }

            @Override
            public void onSuccess(@NonNull Credentials credentials) {
               // Store credentials
               // Navigate to your main activity
            }
    });
}

Whitelist the callback URL for your app in the Allowed Callback URLs section in Application settings. In that section, enter the following URL:

demo://YOUR_AUTH0_DOMAIN/android/YOUR_APP_PACKAGE_NAME/callback

After authentication, the browser redirects the user to your application with the authentication result. The SDK captures the result and parses it.

The AndroidManifest.xml file should look like this:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.auth0.samples">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">

        <activity android:name="com.auth0.samples.MainActivity">
          <intent-filter>
              <action android:name="android.intent.action.MAIN" />
              <category android:name="android.intent.category.LAUNCHER" />
          </intent-filter>
        </activity>

    </application>

</manifest>

There are many options to customize the authentication with the WebAuthProvider builder. You can read about them in the Auth0 SDK for Android documentation.