Google Pay Integration in Mobile App

Integration of Google Pay Payment System into Mobile Application

Google Pay on Android works via Google Pay API — not separate SDK, but part of Google Play Services. Integration technically simpler than Apple Pay: no certificates and separate developer portal, only PaymentDataRequest configuration and token handling. But points where can make mistakes sufficient.

PaymentsClient and ENVIRONMENT_TEST / ENVIRONMENT_PRODUCTION

Google Pay works in two environments. In ENVIRONMENT_TEST can get fake tokens without real card — convenient for development. In ENVIRONMENT_PRODUCTION need pre-pass Google verification (fill form in Google Pay Business Console and get approval).

private fun createPaymentsClient(activity: Activity): PaymentsClient {
    val walletOptions = Wallet.WalletOptions.Builder()
        .setEnvironment(WalletConstants.ENVIRONMENT_PRODUCTION)
        .build()
    return Wallet.getPaymentsClient(activity, walletOptions)
}

PaymentDataRequest configuration

private fun createPaymentDataRequest(price: String): PaymentDataRequest {
    val tokenizationSpec = JSONObject().apply {
        put("type", "PAYMENT_GATEWAY")
        put("parameters", JSONObject().apply {
            put("gateway", "stripe")  // or "cloudpayments", "yookassa" etc
            put("stripe:version", "2023-10-16")
            put("stripe:publishableKey", "pk_live_...")
        })
    }

    val cardPaymentMethod = JSONObject().apply {
        put("type", "CARD")
        put("parameters", JSONObject().apply {
            put("allowedAuthMethods", JSONArray(listOf("PAN_ONLY", "CRYPTOGRAM_3DS")))
            put("allowedCardNetworks", JSONArray(listOf("MASTERCARD", "VISA", "MIR")))
        })
        put("tokenizationSpecification", tokenizationSpec)
    }

    val request = JSONObject().apply {
        put("apiVersion", 2)
        put("apiVersionMinor", 0)
        put("allowedPaymentMethods", JSONArray(listOf(cardPaymentMethod)))
        put("transactionInfo", JSONObject().apply {
            put("totalPrice", price)
            put("totalPriceStatus", "FINAL")
            put("currencyCode", "RUB")
            put("countryCode", "RU")
        })
        put("merchantInfo", JSONObject().apply {
            put("merchantName", "Your Company Name")
            put("merchantId", "YOUR_MERCHANT_ID") // from Business Console
        })
    }

    return PaymentDataRequest.fromJson(request.toString())
}

PAN_ONLY vs CRYPTOGRAM_3DS

Often causes questions. PAN_ONLY — card added to Google Pay via browser or manually, without 3DS token. CRYPTOGRAM_3DS — device with hardware protection (SE or StrongBox), card tokenized in Trusted Execution Environment. For Russian acquirers both methods supported, but clarify with provider — some accept only CRYPTOGRAM_3DS to reduce fraud.

Launch payment interface

private val paymentLauncher = registerForActivityResult(
    ActivityResultContracts.StartIntentSenderForResult()
) { result ->
    when (result.resultCode) {
        Activity.RESULT_OK -> {
            val data = result.data ?: return@registerForActivityResult
            val paymentData = PaymentData.getFromIntent(data)
            val token = paymentData
                ?.paymentMethodToken
                ?.token  // JSON-string with provider token

            // Send token to backend
        }
        Activity.RESULT_CANCELED -> { /* user closed */ }
        AutoResolveHelper.RESULT_ERROR -> {
            val status = AutoResolveHelper.getStatusFromIntent(result.data)
            Log.e("GPay", "Error: ${status?.statusMessage}")
        }
    }
}

// Launch
val task = paymentsClient.loadPaymentData(createPaymentDataRequest("1500.00"))
task.addOnCompleteListener { completedTask ->
    if (completedTask.isSuccessful) {
        paymentLauncher.launch(
            IntentSenderRequest.Builder(
                completedTask.result.resolutionPendingIntent!!.intentSender
            ).build()
        )
    }
}

Google Pay button: design requirements

Google strictly regulates button appearance. Can't change color, font, aspect ratio of Google Pay button. Google checks this during review before ENVIRONMENT_PRODUCTION release.

Correctly use ready widget:

val button = PayButton(context).apply {
    initialize(
        ButtonOptions.newBuilder()
            .setButtonType(ButtonType.BUY)
            .setCornerRadius(8)
            .build()
    )
}

isReadyToPay before showing button

Don't show Google Pay button without check:

val isReadyToPayRequest = IsReadyToPayRequest.fromJson(
    JSONObject().apply {
        put("apiVersion", 2)
        put("apiVersionMinor", 0)
        put("allowedPaymentMethods", JSONArray(listOf(cardPaymentMethod)))
    }.toString()
)

paymentsClient.isReadyToPay(isReadyToPayRequest)
    .addOnSuccessListener { result ->
        googlePayButton.isVisible = result
    }

If card not added to Google Pay or device incompatible — don't show button.

What's included

• PaymentsClient setup with correct environment
• tokenizationSpecification configuration for payment provider
• isReadyToPay implementation and correct button hiding
• PaymentData handling and token passing to backend
• Passing Google Pay Business Console review

Timeline

2–3 days. Cost calculated individually.