Enhancing Android Checkout with Dynamic Callbacks in Google Pay

We are excited to bring Express checkout with Google Pay for Android native apps enabling developers to leverage users stored credentials (payment and address) from Google Wallet to streamline their checkout journeys. You will be able to implement familiar callbacks onPaymentDataChanged

and onPaymentAuthorized

that are already supported on Web now in your Android applications and streamline the checkout funnels. With these callbacks, you can update shipping options, taxes, and total prices dynamically as users interact with the Google Pay sheet, and handle authorization feedback without ever closing the sheet. This is available with play-services-wallet:20.0.0

and onwards.

Why use Dynamic Callbacks?

Dynamic callbacks enable a true "Express Checkout" experience. By moving the Google Pay button upstream to your Product Detail or Cart pages, you can provide the user's shipping address, payment credentials, and contact details all within the Pay sheet.

Getting Started

To get started, update your Google Pay dependency in your build.gradle

file:

com.google.android.gms:play-services-wallet:20.0.0

1. Implement the Callback Logic

Extend BasePaymentDataCallbacks

to handle the specific events triggered during the checkout process.

import com.google.android.gms.wallet.PaymentData

import com.google.android.gms.wallet.callback.BasePaymentDataCallbacks

import com.google.android.gms.wallet.callback.IntermediatePaymentData

import com.google.android.gms.wallet.callback.OnCompleteListener

import com.google.android.gms.wallet.callback.PaymentAuthorizationResult

import com.google.android.gms.wallet.callback.PaymentDataRequestUpdate

import org.json.JSONObject

class MerchantPaymentDataCallbacks : BasePaymentDataCallbacks() {

/**

* Handles payment data changes in the payment sheet such as shipping address and shipping options.

*/

override fun onPaymentDataChanged(

request: IntermediatePaymentData,

onCompleteListener: OnCompleteListener

) {

// Example: Process the request and return updates

// In a real application, you would likely make a network request to your server

// to get updated shipping options and cart details based on the new address.

val shippingAddress = request.shippingAddress

val shippingOptionData = request.shippingOptionData

// Construct the response object

val responseJson = JSONObject().apply {

// Example: Add new shipping options based on the address

put("newShippingOptionParameters", JSONObject().apply {

put("defaultSelectedOptionId", "shipping-001")

put("shippingOptions", JSONObject().apply {

put("id", "shipping-001")

put("label", "$0.00: Free shipping")

put("description", "Free shipping on all orders")

})

})

// Example: Update transaction info

put("newTransactionInfo", JSONObject().apply {

put("totalPriceStatus", "FINAL")

put("totalPrice", "12.34")

put("currencyCode", "USD")

})

}

val response = PaymentDataRequestUpdate.fromJson(responseJson.toString())

onCompleteListener.complete(response)

}

/**

* Called when a payment is authorized in the payment sheet.

*/

override fun onPaymentAuthorized(

request: PaymentData,

onCompleteListener: OnCompleteListener

) {

// Log the payment data for debugging

println("onPaymentAuthorized called with PaymentData: ${request.toJson()}")

// Example: Process the payment authorization

// In a real application, you would send the payment token and other data

// to your server to be processed by your payment service provider.

// Construct the response object

val responseJson = JSONObject().apply {

put("transactionState", "SUCCESS") // Or "ERROR"

// Optionally include an error message

// put("error", JSONObject().apply {

// put("reason", "PAYMENT_DATA_INVALID")

// put("intent", "PAYMENT_AUTHORIZATION")

// put("message", "Invalid payment method.")

// })

}

val response = PaymentAuthorizationResult.fromJson(responseJson.toString())

onCompleteListener.complete(response)

}

}

2. Host the Callback Service

Implement a service that extends BasePaymentDataCallbacksService

to provide an instance of your callbacks.

import androidx.annotation.NonNull

import com.google.android.gms.wallet.callback.BasePaymentDataCallbacks

import com.google.android.gms.wallet.callback.BasePaymentDataCallbacksService

/**

* Service class which hosts the payment data callbacks.

*/

class MerchantPaymentDataCallbacksService : BasePaymentDataCallbacksService() {

@NonNull

override fun createPaymentDataCallbacks(): BasePaymentDataCallbacks {

return MerchantPaymentDataCallbacks()

}

}

3. Update the Android Manifest

You must declare your service and protect it with the BIND_PAYMENTS_CALLBACK_SERVICE

permission.

android:name=".service.MerchantPaymentDataCallbacksService"

android:permission="com.google.android.gms.permission.BIND_PAYMENTS_CALLBACK_SERVICE"

android:exported="true">

4. Configure the Payment Request

Finally, include the callbackIntents

in your PaymentDataRequest

JSON object to tell Google Pay which events you want to listen for.

{

"apiVersion": 2,

"apiVersionMinor": 0,

...

"callbackIntents": [

"PAYMENT_AUTHORIZATION",

"SHIPPING_ADDRESS",

"SHIPPING_OPTION"

]

}

Implementing dynamic callbacks on Android allows you to:

Dynamic callbacks bring the Google Pay developer platform on Android to parity with its capabilities on the web. For a full implementation guide, see the updated developer documentation: goo.gle/pay-android-dpu