Android

Overview

SDK Updates
New versions of the SDK are released frequently, not only to add new features and address issues in the SDK, but also to continuously improve the conversion of merchant login flows. As a result, it is strongly recommended that you frequently update your SDK version across any platforms where you invoke the SDK.

The Knot Link SDK provides a seamless way for end users to link their merchant accounts to your Android app, serving as the foundation for Knot’s merchant connectivity platform. It is a client-side integration, consisting of initializing & configuring the SDK and handling events.

Installation

Add Maven Central

Follow the best-practice installation approach outlined below, which works seamlessly for both Java and Kotlin projects. Adding Maven Central to your root-level build.gradle file ensures that the Android Gradle plugin (and all other dependencies) are properly resolved and kept up-to-date.

allprojects {
    repositories {
        mavenCentral()
    }
}

Add the Knot SDK to your app

In your module-level Gradle file (typically app/build.gradle), configure your Android settings-such as the minimum SDK version and Java 8 support-to ensure compatibility with the SDK. The Knot SDK Requires Android API level 21 or greater.

android {
  defaultConfig {
      minSdkVersion 21 // or greater
  }

  // Enable Java 8 support for KnotAPI SDK
  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }
}

Include the Knot SDK dependency

Include the Knot SDK dependency so that Gradle can fetch the SDK from Maven Central.

implementation group: 'com.knotapi.knot', name: 'knotapi-android-sdk', version: '<latest-version>'

implementation 'com.knotapi.knot:knotapi-android-sdk:<latest-version>'

Replace <latest-version> with the current version provided by Knot.

Import Knot SDK

import com.knotapi.knot.*;

import com.knotapi.knot.*

Initialization

Your backend will create a session by calling Create Session and provide it to your frontend. To initialize the Knot SDK, you must first configure the session with a KnotConfiguration class. The configuration allows you to set the environment, entry point, and other user experience configurations.

It’s expected that your integration with Knot will retrieve and pass a new session into the SDK on each initialization.

Configure the session

The KnotConfiguration and CustomerConfiguration classes are used to initialize the SDK with specific parameters.

`KnotConfiguration`

Name	Type	Description
sessionId	String	The session created by calling `/session/create` in your backend.
clientId	String	Your organization’s client ID. Note that this varies between `development` and `production` environments.
environment	Environment	The desired environment (`development` or `production`).
entryPoint	String	Optional. The specific entry point from within your app where you are initializing the Knot SDK (e.g. `onboarding`). Only alphanumeric characters (a-z, A-Z, 0-9), spaces, ampersands (&), periods (.), and hyphens (-) are allowed.
merchantIds	int[]	Optional. A list of merchant ID(s) to display. It is recommended to provide 0 or 1 merchant IDs depending on your desired user experience.
useCategories	Bool	Optional. Whether to display merchant categories and therefore group merchants into categories for discoverability. Default: `true`.
useSearch	Bool	Optional. Whether to display the search bar, enabling users to search for merchants. Default: `true`.
domainUrls	String[]	Optional. Deprecated in version 3.0.0+. A set of domains for which Knot should explicitly not clear cookies.
metadata	Map<String, String>	Optional. Custom key-value pairs to include in webhook payloads. Maximum 10 keys with string values up to 500 characters each.
locale	String	Optional. A BCP-47 language tag to set the locale for the SDK. Currently supported: `en-US`, `es-US`, `en-CA`, and `fr-CA`. If not provided, defaults to `en-US`.
product	Product	Optional. Ignored in version 2.0.12+. The Knot product the session will inherit — the same as the type of session created (e.g. `card_switcher`, `transaction_link`).

`CustomerConfiguration`

This class is entirely optional and infrequently used, typically only when you offer Knot for multiple, differently-named card programs in the same app. The Knot team will set pre-defined values of your choosing for each parameter that you can then subsequently pass into the SDK. Passing a value that is not pre-defined will result in an onError callback. To take advantage of this functionality, please contact the Knot team who will be happy to assist you.

Name	Type	Description
cardName	String	Optional. The differentiated display name for the card product, used inside the Knot SDK (e.g. `Debit Card`, `Credit Card`). This value will override the default value `card`.
customerName	String	Optional. The differentiated display name for the company, used both as a standalone and prepended to the `cardName` (e.g. `Smart Bank`, `Payment Corp`). This value will override your default customer name value. Only recommended if you issue cards under multiple brands.
logoId	String	Optional. The differentiated logo for the company. This value will override your default logo.

See the following examples for how the parameters are used together in text inside the Knot SDK: "Your [customerName] [cardName | card] was added."

CustomerConfiguration customerConfig = new CustomerConfiguration(
	"Card Name",						  // cardName
	"Customer Name",					  // customerName
	"LogoId"							  // logoId
);

Map<String, String> metadata = new HashMap<>();
metadata.put("reference_token", "your-token");
metadata.put("trace_id", "your-trace-id");

KnotConfiguration config = new KnotConfiguration(
    "session_12345",                      // sessionId
    "client_67890",                       // clientId
    Environment.production,               // environment
    new int[]{101},                       // merchantIds
    true,                                 // useCategories
    true,                                 // useSearch
    new String[]{"https://example.com"},  // domainUrls (deprecated in 3.0.0+)
    "onboarding",                         // entryPoint
    metadata,                             // metadata for webhooks
    customerConfig,
    "es-US"                               // locale (optional BCP-47 language tag)
);

val customerConfig = CustomerConfiguration(
	"Card Name",						  // cardName
	"Customer Name",					  // customerName
	"LogoId"							  // logoId
)

val metadata = mapOf(
    "reference_token" to "your-token",
    "trace_id" to "your-trace-id"
)

val config = KnotConfiguration(
    "session_12345",                      // sessionId
    "client_67890",                       // clientId
    Environment.PRODUCTION,               // environment
    Knot.Product.card_switcher,           // product
    intArrayOf(101, 102, 103),            // merchantIds
    true,                                 // useCategories
    true,                                 // useSearch
    arrayOf("https://example.com"),       // domainUrls (deprecated in 3.0.0+)
    "onboarding",                         // entryPoint
    metadata,                             // metadata for webhooks
    customerConfig,
    "es-US"                               // locale (optional BCP-47 language tag)
)

Open the session

To begin the flow, use the open method with a context, a KnotConfiguration instance, and an optional KnotEventDelegate.

Knot.open(context, knotConfiguration, knotEventDelegate);

Knot.open(context, knotConfiguration, knotEventDelegate)

CustomerConfiguration customerConfig = new CustomerConfiguration(
	"Card Name",						  // cardName
	"Customer Name",					  // customerName
	"LogoId"							  // logoId
);

Map<String, String> metadata = new HashMap<>();
metadata.put("reference_token", "your-token");

KnotConfiguration config = new KnotConfiguration(
    "session_12345",                      // sessionId
    "client_67890",                       // clientId
    Environment.production,               // environment
    new int[]{101},                       // merchantIds
    true,                                 // useCategories
    true,                                 // useSearch
    new String[]{"https://example.com"},  // domainUrls (deprecated in 3.0.0+)
    "onboarding",                         // entryPoint
    metadata,                             // metadata for webhooks
    customerConfig,
    "es-US"                               // locale (optional BCP-47 language tag)
);

Knot.open(context, config, knotEventDelegate);

val customerConfig = CustomerConfiguration(
	"Card Name",						  // cardName
	"Customer Name",					  // customerName
	"LogoId"							  // logoId
)

val metadata = mapOf("reference_token" to "your-token")

val config = KnotConfiguration(
    "session_12345",                      // sessionId
    "client_67890",                       // clientId
    Environment.PRODUCTION,               // environment
    Knot.Product.card_switcher,           // product
    intArrayOf(101, 102, 103),            // merchantIds
    true,                                 // useCategories
    true,                                 // useSearch
    arrayOf("https://example.com"),       // domainUrls (deprecated in 3.0.0+)
    "onboarding",                         // entryPoint
    metadata,                             // metadata for webhooks
    customerConfig,
    "es-US"                               // locale (optional BCP-47 language tag)
)

Knot.open(context, config, knotEventDelegate)

To test logging in to a merchant in the SDK, please reference a set of available test credentials for the CardSwitcher product here and the TransactionLink product here.

Single Merchant Flow

If you decide to use List Merchants to retrieve a list of merchants, list them in your app, and then open the SDK with a single merchant, you can do so by passing a merchant ID when configuring the session in the KnotConfiguration.If a single merchant ID is provided, the user will be sent directly to that merchant’s login experience in the SDK. More in Retrieving & Listing Merchants. The merchant ID is the same across all environments.

Although available, it is not recommended that you provide a long list of merchants in order to remove a few, but rather “hide” certain merchants that you desire from your Customer Dashboard.

Entry Points

In your app’s user experience, you may choose to integrate Knot in one or multiple places (e.g. from different tabs or screens). How users behave when interacting with Knot from each of these “entry points” may vary and it will be useful for you to be able to differentiate these groups of users by entry point in order to assess the value of each entry point. You can provide a value for the entry point in KnotConfiguration.entryPoint when configuring the session . This value will be returned in the AUTHENTICATED webhook.

Categories & Search

Users are presented with a list of merchants in the SDK (unless you provide a single merchant as described above). Accompanying the list is a set of categories and a search experience. Each of these components is visible to users by default (as set in Knot’s backend). You can choose to remove either of them by setting useCategories: false and useSearch: false in KnotConfiguration. This is not recommended.

Events

To receive updates from the SDK, implement KnotEventDelegate in your class.

// Initialize your event delegate
KnotEventDelegate eventDelegate = new KnotEventDelegate() {
    @Override
    public void onSuccess(String merchant) {
        // Handle successful operation
    }

    @Override
    public void onError(KnotError knotError) {
        // Handle error operation using knotError
    }

    @Override
    public void onExit() {
        // Handle SDK exit event
    }

    @Override
    public void onEvent(KnotEvent knotEvent) {
        // Extract and process event details from KnotEvent
    }
};

// Initialize Knot SDK and set the event delegate instance (assuming you have a KnotConfiguration object)
Knot.open(context, knotConfiguration, eventDelegate)

// Initialize your event delegate
val eventDelegate = object : KnotEventDelegate {
    override fun onSuccess(merchant: String) {
        // Handle successful operation
    }

    override fun onError(knotError: KnotError) {
        // Handle error operation using knotError
    }

    override fun onExit() {
        // Handle SDK exit event
    }

    override fun onEvent(knotEvent: KnotEvent) {
        // Extract and process event details from KnotEvent
    }
}

// Initialize Knot SDK and set the event delegate instance (assuming you have a KnotConfiguration object)
Knot.open(context, knotConfiguration, eventDelegate)

`onSuccess`

This event is called when a user successfully logged in to the merchant and their card was switched. This event takes a single string argument representing the merchant’s name.

`onError`

This event is called when an error occurs during SDK initialization. It emits a KnotError enum as described below.

Error Case	Description	Debugging Steps
INVALID_SESSION	The session is invalid.	Ensure `KnotConfiguration.environment` matches the environment the `sessionId` was created for (`development` or `production`).
EXPIRED_SESSION	The session has expired.	Sessions are valid for 30 minutes. It is best practice to ensure that you create a new session every time a user invokes the SDK using Create Session.
INVALID_CLIENT_ID	The client ID is invalid.	Verify that the value you are providing for `KnotConfiguration.clientId` is for the environment matching the value you are providing for `KnotConfiguration.environment` (i.e. `development` or `production`). If you provide your production `clientId` but set `environment: development`, you will experience this error.
INTERNAL_ERROR	An internal error occurred.	Simply retry invoking the SDK with a new `sessionId`.
MERCHANT_ID_NOT_FOUND	The merchant ID is required.	The `type` of `sessionId` you are providing on invokation of the SDK requires that you also provide a value in `KnotConfiguration.merchantIds` to ensure the user is directed to a specific merchant’s login flow in the SDK. You can retrieve a list of merchant IDs (the same in all environments) in List Merchants.
INVALID_CARD_NAME	The card name is invalid.	The value you are providing for `customerConfiguration.cardName` must exactly match an allowlisted value for your organization. Please reach out to the Knot team for access to this allowlist.
INVALID_CUSTOMER_NAME	The customer name is invalid.	The value you are providing for `customerConfiguration.customerName` must exactly match an allowlisted value for your organization. Please reach out to the Knot team for access to this allowlist.
INVALID_LOGO_ID	The logo ID is invalid.	The value you are providing for `customerConfiguration.logoId` must exactly match an allowlisted value for your organization. Please reach out to the Knot team for access to this allowlist.
INVALID_LOCALE	The locale is invalid.	The value you are providing for `KnotConfiguration.locale` must be a valid BCP-47 language tag. Currently supported: `en-US`, `es-US`, `en-CA`, and `fr-CA`.

Sessions are valid for 30 minutes. If a session expires while the SDK is open, an expired session error will be emitted via onError and the SDK will automatically close. To provide a seamless experience, handle the REFRESH_SESSION_REQUEST event via the onEvent callback to proactively extend the session using Extend Session before expiration occurs.

public void onError(KnotError error) {
    switch (error) {
        case INVALID_SESSION:
            Log.e("KnotError", "Error: INVALID_SESSION - " + error.getErrorDescription());
            break;
        case EXPIRED_SESSION:
            Log.e("KnotError", "Error: EXPIRED_SESSION - " + error.getErrorDescription());
            break;
        case INVALID_CLIENT_ID:
            Log.e("KnotError", "Error: INVALID_CLIENT_ID - " + error.getErrorDescription());
            break;
        case INTERNAL_ERROR:
            Log.e("KnotError", "Error: INTERNAL_ERROR - " + error.getErrorDescription());
            break;
		case MERCHANT_ID_NOT_FOUND:
            Log.e("KnotError", "Error: MERCHANT_ID_NOT_FOUND - " +error.getErrorDescription());
            break;
		case INVALID_CARD_NAME:
            Log.e("KnotError", "Error: INVALID_CARD_NAME - " +error.getErrorDescription());
            break;
		case INVALID_CUSTOMER_NAME:
            Log.e("KnotError", "Error: INVALID_CUSTOMER_NAME - " +error.getErrorDescription());
            break;
		case INVALID_LOGO_ID:
            Log.e("KnotError", "Error: INVALID_LOGO_ID - " +error.getErrorDescription());
            break;
		case INVALID_LOCALE:
            Log.e("KnotError", "Error: INVALID_LOCALE - " +error.getErrorDescription());
            break;
    }
}

fun onError(error: KnotError) {
    when (error) {
        KnotError.INVALID_SESSION -> Log.e("KnotError", "Error: INVALID_SESSION - ${error.errorDescription}")
        KnotError.EXPIRED_SESSION -> Log.e("KnotError", "Error: EXPIRED_SESSION - ${error.errorDescription}")
        KnotError.INVALID_CLIENT_ID -> Log.e("KnotError", "Error: INVALID_CLIENT_ID - ${error.errorDescription}")
        KnotError.INTERNAL_ERROR -> Log.e("KnotError", "Error: INTERNAL_ERROR - ${error.errorDescription}")
        KnotError.MERCHANT_ID_NOT_FOUND -> Log.e("KnotError", "Error: MERCHANT_ID_NOT_FOUND - ${error.errorDescription}")
        KnotError.INVALID_CARD_NAME -> Log.e("KnotError", "Error: INVALID_CARD_NAME - The card name is invalid.")
        KnotError.INVALID_CUSTOMER_NAME -> Log.e("KnotError", "Error: INVALID_CUSTOMER_NAME - The customer name is invalid.")
        KnotError.INVALID_LOGO_ID -> Log.e("KnotError", "Error: INVALID_LOGO_ID - ${error.errorDescription}")
        KnotError.INVALID_LOCALE -> Log.e("KnotError", "Error: INVALID_LOCALE - ${error.errorDescription}")
    }
}

`onExit`

This event is called when a user closes the SDK.

`onEvent`

This event is called when certain events occur in the SDK. With this callback, you will be able to understand how a user is progressing through their lifecycle of authenticating to a merchant. It emits a KnotEvent class as described below.

public void onEvent(KnotEvent knotEvent) {
  // Extract event details from the KnotEvent object
   
  // The type of event that occurred (e.g., "MERCHANT_CLICKED", "AUTHENTICATED")
  String eventType = knotEvent.getEvent();
  
  // The product the event emitted from
  String product = knotEvent.getProduct();
  
  // The environment the event emitted from
  String environment = knotEvent.getEnvironment();
  
  // The merchant associated with the event (if applicable)
  String merchant = knotEvent.getMerchantName();

  // The merchant Id associated with the event (if applicable)
  String merchantId = knotEvent.getMerchantId();
  
  // The unique identifier for this specific event instance
  String taskId = knotEvent.getTaskId();
  
  // Additional metadata a key-value map containing extra details related to the event
  Map<String, Object> metadata = knotEvent.getMetaData();
  
  //Additional processing if applicable
}; 

fun onEvent(knotEvent: KnotEvent) {
    // Extract event details from the KnotEvent object

    // The type of event that occurred (e.g., "MERCHANT_CLICKED", "AUTHENTICATED")
    val eventType: String = knotEvent.event
    
    // The product the event emitted from
    val product = knotEvent.getProduct()
    
    // The environment the event emitted from
    val environment = knotEvent.getEnvironment()

    // The merchant associated with the event
    val merchant: String = knotEvent.merchantName

    // The unique identifier for this specific event instance
    val taskId: String = knotEvent.taskId

    // Additional metadata - a key-value map containing extra details related to the event
    val metadata: Map<String, Any> = knotEvent.metaData

    // Additional processing if applicable
}

Below is a list of all possible events emitted via the KnotEvent.event property.

Name	Description
REFRESH_SESSION_REQUEST	Emitted when the session used to initialize the SDK needs to be refreshed. Use Extend Session to extend the session before expiration occurs.
MERCHANT_CLICKED	Emitted when a user clicks on a merchant from the merchant list.
LOGIN_STARTED	Emitted when a user submits their credentials to login to the merchant.
AUTHENTICATED	Emitted when a user successfully logs in to the merchant.
OTP_REQUIRED	Emitted when a user needs to enter an OTP code to login to the merchant.
SECURITY_QUESTIONS_REQUIRED	Emitted when a user needs to enter answers to security questions to login to the merchant.
APPROVAL_REQUIRED	Emitted when a user needs to approve the login - often via a push notification or directly in the merchant’s mobile app - to login to the merchant.
ZIPCODE_REQUIRED	Emitted when a user needs to enter their zip code to login to the merchant.
LICENSE_REQUIRED	Emitted when a user needs to enter their drivers license to login to the merchant.

Other Options

Get current SDK version

If you need to retrieve the current SDK version for your own use case, implement the following:

String sdkVersion = Knot.getSdkVersion();
Log.d("Knot SDK Version", sdkVersion != null ? sdkVersion : "Unknown");

val sdkVersion = Knot.getSdkVersion()
Log.d("Knot SDK Version", sdkVersion ?: "Unknown")

Close the SDK

If you need to explicitly close the SDK, use the below method, otherwise end users will naturally close the SDK as they interact with the interface.

Knot.close();

Knot.close()

Maintain cookies

domainUrls is deprecated in version 3.0.0+ and will be removed in a future release.

Knot clears cookies for security purposes. If your app relies on cookies, you can allowlist specific domains using the domainUrls configuration in KnotConfiguration. This is uncommon.

// The allowed domains for cookies to add as a parameter in KnotConfiguration
String[] domainUrls = new String[]{
    "https://example.com",
    "https://secure.example.com",
    "https://auth.example.com"
};

// The allowed domains for cookies to add as a parameter in KnotConfiguration
val domainUrls = arrayOf(
    "https://example.com",
    "https://secure.example.com",
    "https://auth.example.com"
)

General

SDK

CardSwitcher

SubscriptionManager

TransactionLink

Detect

Vaulting

Shopping

Merchant Account Linking

Overview

Installation

Initialization

Configure the session

`KnotConfiguration`

`CustomerConfiguration`

Open the session

Single Merchant Flow

Entry Points

Categories & Search

Events

`onSuccess`

`onError`

`onExit`

`onEvent`

Other Options

Get current SDK version

Close the SDK

Maintain cookies

​Overview

​Installation

​Initialization

​Configure the session

​KnotConfiguration

​CustomerConfiguration

​Open the session

​Single Merchant Flow

​Entry Points

​Categories & Search

​Events

​onSuccess

​onError

​onExit

​onEvent

​Other Options

​Get current SDK version

​Close the SDK

​Maintain cookies

Overview

Installation

Initialization

Configure the session

`KnotConfiguration`

`CustomerConfiguration`

Open the session

Single Merchant Flow

Entry Points

Categories & Search

Events

`onSuccess`

`onError`

`onExit`

`onEvent`

Other Options

Get current SDK version

Close the SDK

Maintain cookies