🛠️ OnePref + InAppEngine

This package is endorsed, which means you can simply use shared_preferences and in_app_purchase normally.
This package will be automatically included in your app when you do — no need to add it manually to your pubspec.yaml.

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✨ Features

OnePref provides the same functionality as shared_preferences, but in a simpler, developer-friendly API.
Additionally, it includes an InAppEngine utility that helps you integrate in-app purchases quickly and safely — saving you hours of setup time.

Key Highlights

• 🚀 Simplified preference storage using OnePref.
• 💰 Streamlined in-app purchase management for Android & iOS.
• 🧾 Support for both consumable and non-consumable products.
• 🔁 Built-in subscription upgrade/downgrade support (Android).
• 🧩 Easy product query and restore logic.
• 🧠 Debug-friendly logs and structured PurchaseResult.

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🚀 Getting Started

1️⃣ Install

flutter pub add onepref

import 'package:onepref/onepref.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await OnePref.init();
  runApp(const MyApp());
}

Write a value

await OnePref.setString("key", "value here");
await OnePref.setBool("darkMode", true);
await OnePref.setInt("launchCount", 5);

Read a value

final value = OnePref.getString("key");
final isDark = OnePref.getBool("darkMode");
final count  = OnePref.getInt("launchCount");

Premium & Remove Ads helpers

// Write
await OnePref.setPremium(true);
await OnePref.setRemoveAds(true);

// Read
final isPremium   = OnePref.getPremium();
final noAds       = OnePref.getRemoveAds();

Other Utilities

// Check whether a key exists
final exists = OnePref.containsKey("key");

// String list support
await OnePref.setStringList("items", ["a", "b", "c"]);
final items = OnePref.getStringList("items");

// Remove a single key or everything
await OnePref.removeKey("key");
await OnePref.removeAllSavedPrefs();

---

🛒 Usage (In-App Purchases)

⚠️ ATTENTION!

Before using InAppEngine, make sure you have correctly configured in-app purchases
in the Play Console (Android) or App Store Connect (iOS).

Setup variables

late final List<String> _notFoundIds = <String>[];
late final List<ProductDetails> _products = <ProductDetails>[];
late final List<PurchaseDetails> _purchases = <PurchaseDetails>[];
late bool _isAvailable = false;
late bool _purchasePending = false;

final InAppEngine inAppEngine = InAppEngine.instance;

Define your products

const storeProductIds = [
  InAppEngineProductId(id: "premium_monthly", isConsumable: false, isSubscription: true),
  InAppEngineProductId(id: "remove_ads",      isConsumable: false, isOneTimePurchase: true),
  InAppEngineProductId(id: "coins_100",       isConsumable: true,  reward: 100),
];

Initialize and Query Products

@override
void initState() {
  super.initState();

  // Listen to purchase updates
  inAppEngine.inAppPurchase.purchaseStream.listen(
    (List<PurchaseDetails> purchaseDetailsList) {
      listenToPurchaseUpdated(purchaseDetailsList);
    },
    onDone: () {},
    onError: (Object error) {
      debugPrint("Purchase Stream Error: $error");
    },
  );

  getProducts(); // Fetch product details
}

Future<void> getProducts() async {
  final isAvailable = await inAppEngine.getIsAvailable();

  if (isAvailable) {
    final response = await inAppEngine.queryProducts(storeProductIds);

    setState(() {
      _isAvailable = isAvailable;
      _products.addAll(response.productDetails);
      _notFoundIds.addAll(response.notFoundIDs);
      _purchasePending = false;
    });
  } else {
    debugPrint("Store not available.");
  }
}

Handle a Purchase

TextButton(
  onPressed: () async {
    final selected = _products[selectedProduct ?? 0];
    final initiated = await inAppEngine.handlePurchase(selected, storeProductIds);
    if (!initiated) {
      debugPrint("Could not initiate purchase.");
    }
  },
  child: Text(
    "Buy $reward",
    textAlign: TextAlign.center,
    style: const TextStyle(
      color: Colors.white,
      fontSize: 14,
      fontWeight: FontWeight.normal,
    ),
  ),
),

Handle Purchase Results

Future<void> listenToPurchaseUpdated(
    List<PurchaseDetails> purchaseDetailsList) async {
  final results = await inAppEngine.purchaseListener(
    purchaseDetailsList: purchaseDetailsList,
    productsIds: storeProductIds,
  );

  for (final result in results) {
    if (result.purchaseComplete == true) {
      debugPrint("Purchase completed: ${result.productId}");
      await OnePref.setPremium(true);
    } else if (result.purchaseRestore == true) {
      debugPrint("Purchase restored: ${result.productId}");
      await OnePref.setPremium(true);
    } else if (result.purchaseConsumed == true) {
      debugPrint("Consumable consumed: ${result.productId}");
    } else if (result.message != null) {
      debugPrint("Purchase message: ${result.message}");
    }
  }
}

🧩 Restoring Purchases

ElevatedButton(
  onPressed: () async {
    await inAppEngine.restorePurchases();
    // Results arrive via the purchaseStream listener above
  },
  child: const Text("Restore Purchases"),
),

🔄 Subscription Upgrade / Downgrade (Android only)

final success = await inAppEngine.upgradeOrDowngradeSubscription(
  currentSubPurchaseDetails, // existing GooglePlayPurchaseDetails
  newSubProductDetails,      // new ProductDetails
);

Feature	Description
🔹 Shared Preferences	Simple key/value storage with OnePref
🔹 Product Query	Fetch Play/App Store products easily
🔹 Purchase Handling	Buy consumables & non-consumables
🔹 Subscription	Manage upgrades/downgrades on Android
🔹 Restore	Restore past purchases with one line
🔹 Debug Logging	Built-in safe logging for dev mode