提供其他結帳系統 (包括使用者自選的其他結帳系統) 的應用程式內整合指南

val purchasesUpdatedListener =
   PurchasesUpdatedListener { billingResult, purchases ->
       // Handle new Google Play purchase.
   }

val userChoiceBillingListener =
   UserChoiceBillingListener { userChoiceDetails ->
       // Handle alternative billing choice.
   }

var billingClient = BillingClient.newBuilder(context)
   .setListener(purchasesUpdatedListener)
   .enablePendingPurchases()
   .enableUserChoiceBilling(userChoiceBillingListener)
   .build()

private PurchasesUpdatedListener purchasesUpdatedListener = new PurchasesUpdatedListener() {
    @Override
    public void onPurchasesUpdated(BillingResult billingResult, List<Purchase> purchases) {
        // Handle new Google Play purchase.
    }
};

private UserChoiceBillingListener userChoiceBillingListener = new UserChoiceBillingListener() {
    @Override
    public void userSelectedAlternativeBilling(
        UserChoiceDetails userChoiceDetails) {
        // Handle new Google Play purchase.
    }
};

private BillingClient billingClient = BillingClient.newBuilder(context)
    .setListener(purchasesUpdatedListener)
    .enablePendingPurchases()
    .enableUserChoiceBilling(userChoiceBillingListener)
    .build();

private val userChoiceBillingListener =
    UserChoiceBillingListener { userChoiceDetails ->
        // Get the products being purchased by the user.
        val products = userChoiceDetails.products

        // Send external transaction token to developer backend server
        // this devBackend object is for demonstration purposes,
        // developers can implement this step however best fits their
        // app to backend communication.
        devBackend.sendExternalTransactionStarted(
            userChoiceDetails.externalTransactionToken,
            user
        )

        // Launch alternative billing
        // ...
        // The developer backend handles reporting the transaction
        // to Google Play's backend once the alternative billing
        // purchase is completed.
    }

private userChoiceBillingListener userChoiceBillingListener = new UserChoiceBillingListener() {
    @Override
    public void userSelectedAlternativeBilling(
           UserChoiceDetails userChoiceDetails) {
       // Get the products being purchased by the user.
       List<Product> products =
              userChoiceDetails.getProducts();

       // Send external transaction token to developer backend server
       // this devBackend object is for demonstration purposes,
       // developers can implement this step however best fits their
       // app to backend communication.
       devBackend.sendExternalTransactionStarted(
              userChoiceDetails.getExternalTransactionToken(),
              user
       );

       // Launch alternative billing
       // ...
       // The developer backend handles reporting the transaction
       // to Google Play's backend once the alternative billing
       // purchase is completed.
    }
};

// The external transaction ID from the current
// alternative billing subscription.
val externalTransactionId = //... ;

val billingFlowParams = BillingFlowParams.newBuilder()
    .setProductDetailsParamsList(
        listOf(
            BillingFlowParams.ProductDetailsParams.newBuilder()
                // Fetched via queryProductDetailsAsync.
                .setProductDetails(productDetailsNewPlan)
                // offerIdToken can be found in
                // ProductDetails=>SubscriptionOfferDetails.
                .setOfferToken(offerTokenNewPlan)
                .build()
        )
    )
    .setSubscriptionUpdateParams(
        BillingFlowParams.SubscriptionUpdateParams.newBuilder()
            .setOriginalExternalTransactionId(externalTransactionId)
            .build()

val billingResult = billingClient.launchBillingFlow(activity, billingFlowParams)

// When the user selects the alternative billing flow,
// the UserChoiceBillingListener is triggered.

// The external transaction ID from the current
// alternative billing subscription.
String externalTransactionId = //... ;

BillingFlowParams billingFlowParams =
        BillingFlowParams.newBuilder()
            .setProductDetailsParamsList(
                ImmutableList.of(
                    ProductDetailsParams.newBuilder()
                        // Fetched via queryProductDetailsAsync.
                        .setProductDetails(productDetailsNewPlan)
                        // offerIdToken can be found in
                        // ProductDetails=>SubscriptionOfferDetails
                        .setOfferToken(offerTokenNewPlan)
                    .build()
                )
            )
            .setSubscriptionUpdateParams(
                SubscriptionUpdateParams.newBuilder()
                    .setOriginalExternalTransactionId(externalTransactionId)
                    .build()
            )
            .build();

BillingResult billingResult = billingClient.launchBillingFlow(activity, billingFlowParams);

// When the user selects the alternative billing flow,
// the UserChoiceBillingListener is triggered.