A storefront-independent API for purchases in Flutter apps.

This plugin supports in-app purchases (IAP) through an underlying store, which can be the App Store (on iOS) or Google Play (on Android).

This plugin is in beta. Use it with caution and file any potential issues you see.

Features

Use this plugin in your Flutter app to:

• Show in-app products that are available for sale from the underlying store. Products can include consumables, permanent upgrades, and subscriptions.
• Load in-app products that the user owns.
• Send the user to the underlying store to purchase products.
• Present a UI for redeeming subscription offer codes. (iOS 14 only)

Getting started

This plugin relies on the App Store and Google Play for making in-app purchases. It exposes a unified surface, but you still need to understand and configure your app with each store. Both stores have extensive guides:

• App Store documentation
• Google Play documentation

For a list of steps for configuring in-app purchases in both stores, see the example app README.

Once you've configured your in-app purchases in their respective stores, you can start using the plugin. Two basic options are available:

1. A generic, idiomatic Flutter API: in_app_purchase. This API supports most use cases for loading and making purchases.

2. Platform-specific Dart APIs: store_kit_wrappers and billing_client_wrappers. These APIs expose platform-specific behavior and allow for more fine-tuned control when needed. However, if you use one of these APIs, your purchase-handling logic is significantly different for the different storefronts.

Usage

This section has examples of code for the following tasks:

• Initializing the plugin
• Listening to purchase updates
• Connecting to the underlying store
• Loading products for sale
• Loading previous purchases
• Making a purchase
• Completing a purchase
• Upgrading or downgrading an existing in-app subscription
• Presenting a code redemption sheet (iOS 14)

Initializing the plugin

The following initialization code is required for Google Play:

void main() {
  // Inform the plugin that this app supports pending purchases on Android.
  // An error will occur on Android if you access the plugin `instance`
  // without this call.
  //
  // On iOS this is a no-op.
  InAppPurchaseConnection.enablePendingPurchases();
  runApp(MyApp());
}

Listening to purchase updates

In your app's initState method, subscribe to any incoming purchases. These can propagate from either underlying store. You should always start listening to purchase update as early as possible to be able to catch all purchase updates, including the ones from the previous app session. To listen to the update:

class _MyAppState extends State<MyApp> {
  StreamSubscription<List<PurchaseDetails>> _subscription;

  @override
  void initState() {
    final Stream purchaseUpdated =
        InAppPurchaseConnection.instance.purchaseUpdatedStream;
    _subscription = purchaseUpdated.listen((purchaseDetailsList) {
      _listenToPurchaseUpdated(purchaseDetailsList);
    }, onDone: () {
      _subscription.cancel();
    }, onError: (error) {
      // handle error here.
    });
    super.initState();
  }

  @override
  void dispose() {
    _subscription.cancel();
    super.dispose();
  }

Here is an example of how to handle purchase updates:

void _listenToPurchaseUpdated(List<PurchaseDetails> purchaseDetailsList) {
  purchaseDetailsList.forEach((PurchaseDetails purchaseDetails) async {
    if (purchaseDetails.status == PurchaseStatus.pending) {
      _showPendingUI();
    } else {
      if (purchaseDetails.status == PurchaseStatus.error) {
        _handleError(purchaseDetails.error!);
      } else if (purchaseDetails.status == PurchaseStatus.purchased) {
        bool valid = await _verifyPurchase(purchaseDetails);
        if (valid) {
          _deliverProduct(purchaseDetails);
        } else {
          _handleInvalidPurchase(purchaseDetails);
          return;
        }
      }
      if (purchaseDetails.pendingCompletePurchase) {
        await InAppPurchaseConnection.instance
            .completePurchase(purchaseDetails);
      }
    }
  });
}

Connecting to the underlying store

final bool available = await InAppPurchaseConnection.instance.isAvailable();
if (!available) {
  // The store cannot be reached or accessed. Update the UI accordingly.
}

Loading products for sale

// Set literals require Dart 2.2. Alternatively, use
// `Set<String> _kIds = <String>['product1', 'product2'].toSet()`.
const Set<String> _kIds = <String>{'product1', 'product2'};
final ProductDetailsResponse response =
    await InAppPurchaseConnection.instance.queryProductDetails(_kIds);
if (response.notFoundIDs.isNotEmpty) {
  // Handle the error.
}
List<ProductDetails> products = response.productDetails;

Loading previous purchases

In the following example, implement _verifyPurchase so that it verifies the purchase following the best practices for each underlying store:

• Verifying App Store purchases
• Verifying Google Play purchases

final QueryPurchaseDetailsResponse response =
    await InAppPurchaseConnection.instance.queryPastPurchases();
if (response.error != null) {
  // Handle the error.
}
for (PurchaseDetails purchase in response.pastPurchases) {
  // Verify the purchase following best practices for each underlying store.
  _verifyPurchase(purchase);
  // Deliver the purchase to the user in your app.
  _deliverPurchase(purchase);
  if (purchase.pendingCompletePurchase) {
    // Mark that you've delivered the purchase. This is mandatory.
    InAppPurchaseConnection.instance.completePurchase(purchase);
  }
}

Note that the App Store does not have any APIs for querying consumable products, and Google Play considers consumable products to no longer be owned once they‘re marked as consumed and fails to return them here. For restoring these across devices you’ll need to persist them on your own server and query that as well.

Making a purchase

Both underlying stores handle consumable and non-consumable products differently. If you're using InAppPurchaseConnection, you need to make a distinction here and call the right purchase method for each type.

final ProductDetails productDetails = ... // Saved earlier from queryPastPurchases().
final PurchaseParam purchaseParam = PurchaseParam(productDetails: productDetails);
if (_isConsumable(productDetails)) {
  InAppPurchaseConnection.instance.buyConsumable(purchaseParam: purchaseParam);
} else {
  InAppPurchaseConnection.instance.buyNonConsumable(purchaseParam: purchaseParam);
}
// From here the purchase flow will be handled by the underlying store.
// Updates will be delivered to the `InAppPurchaseConnection.instance.purchaseUpdatedStream`.

Completing a purchase

The InAppPurchaseConnection.purchaseUpdatedStream will send purchase updates after you initiate the purchase flow using InAppPurchaseConnection.buyConsumable or InAppPurchaseConnection.buyNonConsumable. After delivering the content to the user, call InAppPurchaseConnection.completePurchase to tell the App Store and Google Play that the purchase has been finished.

Warning: Failure to call InAppPurchaseConnection.completePurchase and get a successful response within 3 days of the purchase will result a refund.

Upgrading or downgrading an existing in-app subscription

To upgrade/downgrade an existing in-app subscription in Google Play, you need to provide an instance of ChangeSubscriptionParam with the old PurchaseDetails that the user needs to migrate from, and an optional ProrationMode with the PurchaseParam object while calling InAppPurchaseConnection.buyNonConsumable.

The App Store does not require this because it provides a subscription grouping mechanism. Each subscription you offer must be assigned to a subscription group. Grouping related subscriptions together can help prevent users from accidentally purchasing multiple subscriptions. Refer to the Creating a Subscription Group section of Apple's subscription guide.

final PurchaseDetails oldPurchaseDetails = ...;
PurchaseParam purchaseParam = PurchaseParam(
    productDetails: productDetails,
    changeSubscriptionParam: ChangeSubscriptionParam(
        oldPurchaseDetails: oldPurchaseDetails,
        prorationMode: ProrationMode.immediateWithTimeProration));
InAppPurchaseConnection.instance
    .buyNonConsumable(purchaseParam: purchaseParam);

Presenting a code redemption sheet (iOS 14)

The following code brings up a sheet that enables the user to redeem offer codes that you've set up in App Store Connect. For more information on redeeming offer codes, see Implementing Offer Codes in Your App.

InAppPurchaseConnection.instance.presentCodeRedemptionSheet();

Contributing to this plugin

This plugin uses json_serializable for the many data structs passed between the underlying platform layers and Dart. After editing any of the serialized data structs, rebuild the serializers by running flutter packages pub run build_runner build --delete-conflicting-outputs. flutter packages pub run build_runner watch --delete-conflicting-outputs will watch the filesystem for changes.

If you would like to contribute to the plugin, check out our contribution guide.