Enhancing Android Checkout with Dynamic Callbacks in Google Pay

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<PaymentDataRequestUpdate>
    ) {

        // 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<PaymentAuthorizationResult>
    ) {
        // 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)
    }
}

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()
    }
}

<service
    android:name=".service.MerchantPaymentDataCallbacksService"
    android:permission="com.google.android.gms.permission.BIND_PAYMENTS_CALLBACK_SERVICE"
    android:exported="true">
    <intent-filter>
        <action android:name="com.google.android.gms.wallet.callback.PAYMENT_DATA_CALLBACKS" />
    </intent-filter>
</service>

{
  "apiVersion": 2,
  "apiVersionMinor": 0,
  ...
  "callbackIntents": [
    "PAYMENT_AUTHORIZATION",
    "SHIPPING_ADDRESS",
    "SHIPPING_OPTION"
  ]
}