API Overview

Flutter In-App Purchase provides a comprehensive API for managing in-app purchases across iOS and Android platforms.

Core Classes

FlutterInappPurchase

The main class providing all IAP functionality:

class FlutterInappPurchase {
  static FlutterInappPurchase get instance => _instance;

  // Connection management
  Future<String?> initialize();
  Future<String?> endConnection();

  // Product management
  Future<List<IapItem>> requestProducts({
    required List<String> skus,
    PurchaseType type = PurchaseType.inapp,
  });

  // Purchase management
  Future<void> requestPurchase(String sku);
  Future<void> requestSubscription(String sku);
  Future<List<PurchasedItem>?> getAvailablePurchases();

  // Transaction management
  Future<String?> finishTransaction(Purchase purchase, {bool isConsumable = false});
  // Android helpers
  Future<String?> acknowledgePurchaseAndroid({required String purchaseToken});
  Future<String?> consumePurchaseAndroid({required String purchaseToken});

  // Streams (expo-iap compatible)
  Stream<Purchase> get purchaseUpdatedListener;
  Stream<PurchaseError> get purchaseErrorListener;
}

IapItem

Represents a product or subscription:

class IapItem {
  final String? productId;
  final String? price;
  final String? currency;
  final String? localizedPrice;
  final String? title;
  final String? description;

  // iOS specific fields
  final String? introductoryPrice;
  final String? introductoryPricePaymentModeIOS;
  final String? introductoryPriceNumberOfPeriodsIOS;
  final String? introductoryPriceSubscriptionPeriodIOS;
  final String? subscriptionPeriodNumberIOS;
  final String? subscriptionPeriodUnitIOS;

  // Android specific fields
  final String? signatureAndroid;
  final String? originalJsonAndroid;
  final String? developerPayloadAndroid;
  final String? isConsumableAndroid;
}

PurchasedItem

Represents a completed purchase:

class PurchasedItem {
  final String? productId;
  final String? transactionId;
  final DateTime? transactionDate;
  final String? transactionReceipt;
  final String? purchaseToken;

  // iOS specific
  final String? originalTransactionDateIOS;
  final String? originalTransactionIdentifierIOS;

  // Android specific
  final String? purchaseTokenAndroid;  // [DEPRECATED] Use purchaseToken instead
  final String? developerPayloadAndroid;
  final bool? isAcknowledgedAndroid;
  final int? purchaseStateAndroid;
  final String? packageNameAndroid;
}

Key Methods

Connection Management

initialize()

Future<String?> initialize() async

Establishes connection to the store. Must be called before any other methods.

Returns: Connection result message or error

Example:

String? result = await FlutterInappPurchase.instance.initialize();
if (result == 'Billing is unavailable') {
  // Handle unavailable billing
}

Product Management

requestProducts()

Future<List<IapItem>> requestProducts({
  required List<String> skus,
  PurchaseType type = PurchaseType.inapp,
}) async

Fetches product or subscription information for the given SKUs.

Parameters:

• skus: List of product identifiers
• type: Product type - PurchaseType.inapp (regular) or PurchaseType.subs (subscriptions)

Returns: List of available products or subscriptions

Examples:

// Get regular products (consumables and non-consumables)
List<IapItem> products = await FlutterInappPurchase.instance
    .requestProducts(skus: ['coin_pack_100', 'remove_ads'], type: PurchaseType.inapp);

// Get subscriptions
List<IapItem> subscriptions = await FlutterInappPurchase.instance
    .requestProducts(skus: ['premium_monthly', 'premium_yearly'], type: PurchaseType.subs);

Purchase Management

requestPurchase()

Future<void> requestPurchase(String sku) async

Initiates a purchase for the specified product.

Parameters:

• sku: Product identifier to purchase

Throws: PlatformException if purchase fails

Example:

try {
  await FlutterInappPurchase.instance.requestPurchase('remove_ads');
  // Purchase result delivered via purchaseUpdated stream
} catch (e) {
  // Handle purchase error
}

getAvailablePurchases()

Future<List<PurchasedItem>?> getAvailablePurchases() async

Retrieves all available purchases (including pending and non-consumed).

Returns: List of purchases or null

Transaction Management

finishTransaction()

Future<String?> finishTransaction(Purchase purchase, {bool isConsumable = false}) async

Completes a transaction and removes it from the queue.

Parameters:

• purchase: The purchase to finish

Returns: Result message or null

consumePurchaseAndroid()

Future<String?> consumePurchaseAndroid({required String purchaseToken}) async

Android only: Consumes a purchase, allowing it to be purchased again.

Parameters:

• purchaseToken: The purchase token from the purchase

Returns: Result message or null

acknowledgePurchaseAndroid()

Future<String?> acknowledgePurchaseAndroid({required String purchaseToken}) async

Android only: Acknowledges a non-consumable purchase.

Parameters:

• purchaseToken: The purchase token from the purchase

Returns: Result message or null

Streams

purchaseUpdatedListener

Stream<Purchase> get purchaseUpdatedListener

Stream of successful purchase updates (expo-iap compatible).

Example:

FlutterInappPurchase.instance.purchaseUpdatedListener.listen((purchase) {
  // Handle successful purchase
  print('Purchased: ${purchase.productId}');
});

purchaseErrorListener

Stream<PurchaseError> get purchaseErrorListener

Stream of purchase errors (expo-iap compatible).

Example:

FlutterInappPurchase.instance.purchaseErrorListener.listen((error) {
  // Handle purchase error
  print('Purchase failed: ${error.message}');
});

Platform-Specific Features

iOS Specific

// Get App Store receipt
Future<String?> getReceiptData() async

// Validate receipt locally
Future<Map<String, dynamic>?> validateReceiptIos({
  required String receiptBody,
  bool isTest = true,
}) async

// Get promoted product
Future<String?> getPromotedProduct() async

// Request product info
Future<List<IapItem>> getProductsIOS(List<String> skus) async

Android Specific

// Get purchase history
Future<List<PurchasedItem>?> getPurchaseHistoryAndroid() async

// Enable debug mode
void setDebugMode(bool enabled)

// Check if item is consumed
bool isConsumableAndroid(String productId)

Error Handling

Common error codes:

class IAPError {
  static const String E_UNKNOWN = 'E_UNKNOWN';
  static const String E_USER_CANCELLED = 'E_USER_CANCELLED';
  static const String E_NETWORK = 'E_NETWORK';
  static const String E_ITEM_UNAVAILABLE = 'E_ITEM_UNAVAILABLE';
  static const String E_REMOTE_ERROR = 'E_REMOTE_ERROR';
  static const String E_NOT_PREPARED = 'E_NOT_PREPARED';
  static const String E_ALREADY_OWNED = 'E_ALREADY_OWNED';
}

Usage Patterns

Basic Purchase Flow

// 1. Initialize
await FlutterInappPurchase.instance.initialize();

// 2. Set up listeners
FlutterInappPurchase.instance.purchaseUpdatedListener.listen(handlePurchase);

// 3. Load products
var products = await FlutterInappPurchase.instance.requestProducts(
  skus: productIds,
  type: PurchaseType.inapp
);

// 4. Request purchase
await FlutterInappPurchase.instance.requestPurchase(productId);

// 5. Handle in listener
void handlePurchase(Purchase purchase) {
  // Verify, deliver, and finish
}

Subscription Flow

// 1. Load subscriptions
var subs = await FlutterInappPurchase.instance.requestProducts(
  skus: subIds,
  type: PurchaseType.subs
);

// 2. Request subscription
await FlutterInappPurchase.instance.requestSubscription(subId);

// 3. Check active subscriptions
var purchases = await FlutterInappPurchase.instance.getAvailablePurchases();
var activeSubs = purchases?.where((p) => isSubscriptionActive(p));

Next Steps

• Method Reference - Detailed method documentation
• Type Reference - Type definitions
• Error Codes - Complete error code reference