问在app购买中颤动，检查购买是否成功

EN

const List<String> _kProductIds = <String>[
  'subscription_gold',
];

class paymentScreen extends StatefulWidget {
  @override
  _paymentScreenState createState() => _paymentScreenState();
}

class _paymentScreenState extends State<paymentScreen> {
  final _formKey = GlobalKey<FormState>();
  final TextEditingController userLink = new TextEditingController();
  String accestoken = accessTokenGlobal;

  final InAppPurchase _inAppPurchase = InAppPurchase.instance;
  late StreamSubscription<List<PurchaseDetails>> _subscription;
  List<String> _notFoundIds = [];
  List<ProductDetails> _products = [];
  List<PurchaseDetails> _purchases = [];
  List<String> _consumables = [];
  bool _isAvailable = false;
  bool _purchasePending = false;
  bool _loading = true;
  String? _queryProductError;

  @override
  void initState() {
    final Stream<List<PurchaseDetails>> purchaseUpdated =
        _inAppPurchase.purchaseStream;
    _subscription = purchaseUpdated.listen((purchaseDetailsList) {
      _listenToPurchaseUpdated(purchaseDetailsList);
    }, onDone: () {
      _subscription.cancel();
    }, onError: (error) {
      // handle error here.
    });
    initStoreInfo();
    super.initState();
  }

  Future<void> initStoreInfo() async {
    final bool isAvailable = await _inAppPurchase.isAvailable();
    if (!isAvailable) {
      setState(() {
        _isAvailable = isAvailable;
        _products = [];
        _purchases = [];
        _notFoundIds = [];
        _consumables = [];
        _purchasePending = false;
        _loading = false;
      });
      return;
    }

    if (Platform.isIOS) {
      var iosPlatformAddition = _inAppPurchase
          .getPlatformAddition<InAppPurchaseIosPlatformAddition>();
      await iosPlatformAddition.setDelegate(ExamplePaymentQueueDelegate());
    }

    ProductDetailsResponse productDetailResponse =
        await _inAppPurchase.queryProductDetails(_kProductIds.toSet());
    if (productDetailResponse.error != null) {
      setState(() {
        _queryProductError = productDetailResponse.error!.message;
        _isAvailable = isAvailable;
        _products = productDetailResponse.productDetails;
        _purchases = [];
        _notFoundIds = productDetailResponse.notFoundIDs;
        _consumables = [];
        _purchasePending = false;
        _loading = false;
      });
      return;
    }

    if (productDetailResponse.productDetails.isEmpty) {
      setState(() {
        _queryProductError = null;
        _isAvailable = isAvailable;
        _products = productDetailResponse.productDetails;
        _purchases = [];
        _notFoundIds = productDetailResponse.notFoundIDs;
        _consumables = [];
        _purchasePending = false;
        _loading = false;
      });
      return;
    }

    List<String> consumables = await ConsumableStore.load();
    setState(() {
      _isAvailable = isAvailable;
      _products = productDetailResponse.productDetails;
      _notFoundIds = productDetailResponse.notFoundIDs;
      _consumables = consumables;
      _purchasePending = false;
      _loading = false;
    });
  }

  @override
  void dispose() {
    if (Platform.isIOS) {
      var iosPlatformAddition = _inAppPurchase
          .getPlatformAddition<InAppPurchaseIosPlatformAddition>();
      iosPlatformAddition.setDelegate(null);
    }
    _subscription.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    double Width = MediaQuery.of(context).size.width;
    double Height = MediaQuery.of(context).size.height;
    double Status = MediaQuery.of(context).padding.top;

    return Scaffold(
      bottomNavigationBar: Padding(
        padding: const EdgeInsets.all(8.0),
        child: GestureDetector(
          onTap: () {
            print(_products);

            showModalBottomSheet(
                context: context,
                builder: (context) {
                  return StatefulBuilder(builder: (BuildContext context,
                      StateSetter setState /*You can rename this!*/) {
                    return Container(
                        height: 200,
                        child: ListView(
                          children: [
                            _buildProductList(),
                          ],
                        ));
                  });
                });
          },
          child: Container(
            width: Width * 0.9,
            height: Height * 0.06,
            decoration: BoxDecoration(
                color: kPrimaryColor, borderRadius: BorderRadius.circular(5)),
            child: Center(
              child: Text(
                'Subscribe Now',
                style: TextStyle(
                    color: Colors.white, fontSize: 16, fontFamily: 'SegoeUI'),
              ),
            ),
          ),
        ),
      ),
    );
  }

 
  Card _buildProductList() {
    if (_loading) {
      return Card(
          child: (ListTile(
              leading: CircularProgressIndicator(),
              title: Text('Fetching products...'))));
    }
    if (!_isAvailable) {
      return Card();
    }
    final ListTile productHeader = ListTile(title: Text('Subscriptions'));
    List<ListTile> productList = <ListTile>[];
    if (_notFoundIds.isNotEmpty) {
      productList.add(ListTile(
          title: Text('[${_notFoundIds.join(", ")}] not found',
              style: TextStyle(color: ThemeData.light().errorColor)),
          subtitle: Text(
              'This app needs special configuration to run. Please see example/README.md for instructions.')));
    }

    // This loading previous purchases code is just a demo. Please do not use this as it is.
    // In your app you should always verify the purchase data using the `verificationData` inside the [PurchaseDetails] object before trusting it.
    // We recommend that you use your own server to verify the purchase data.
    Map<String, PurchaseDetails> purchases =
        Map.fromEntries(_purchases.map((PurchaseDetails purchase) {
      if (purchase.pendingCompletePurchase) {
        _inAppPurchase.completePurchase(purchase);
      }
      return MapEntry<String, PurchaseDetails>(purchase.productID, purchase);
    }));
    productList.addAll(_products.map(
      (ProductDetails productDetails) {
        PurchaseDetails? previousPurchase = purchases[productDetails.id];
        var date = DateTime.now().toString();

        var dateParse = DateTime.parse(date);

        var formattedDate =
            "${dateParse.day}-${dateParse.month}-${dateParse.year + 1}";

        return ListTile(
            title: Text(
              'Yearly',
            ),
            subtitle: Text(
              'Your subscription will expire on ${formattedDate}',
            ),
            trailing: previousPurchase != null
                ? IconButton(
                    onPressed: () => confirmPriceChange(context),
                    icon: Icon(Icons.upgrade))
                : TextButton(
                    child: Text(productDetails.price),
                    style: TextButton.styleFrom(
                      backgroundColor: kPrimaryColor,
                      primary: Colors.white,
                    ),
                    onPressed: () {
                      late PurchaseParam purchaseParam;

                      if (Platform.isAndroid) {
                        // NOTE: If you are making a subscription purchase/upgrade/downgrade, we recommend you to
                        // verify the latest status of you your subscription by using server side receipt validation
                        // and update the UI accordingly. The subscription purchase status shown
                        // inside the app may not be accurate.
                        final oldSubscription =
                            _getOldSubscription(productDetails, purchases);

                        purchaseParam = GooglePlayPurchaseParam(
                            productDetails: productDetails,
                            applicationUserName: null,
                            changeSubscriptionParam: (oldSubscription != null)
                                ? ChangeSubscriptionParam(
                                    oldPurchaseDetails: oldSubscription,
                                    prorationMode: ProrationMode
                                        .immediateWithTimeProration,
                                  )
                                : null);
                      } else {
                        purchaseParam = PurchaseParam(
                          productDetails: productDetails,
                          applicationUserName: null,
                        );
                      }

                      if (productDetails.id == _kConsumableId) {
                        _inAppPurchase.buyConsumable(
                            purchaseParam: purchaseParam,
                            autoConsume: _kAutoConsume || Platform.isIOS);
                      } else {
                        _inAppPurchase.buyNonConsumable(
                            purchaseParam: purchaseParam);
                      }
                    },
                  ));
      },
    ));

    return Card(
        child: Column(
            children: <Widget>[
                  Container(
                    color: Color(0xfff5f6fb),
                    child: Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Center(
                          child: Text(
                        'You can cancel subscription from playstore.',
                        style: TextStyle(
                            fontFamily: 'PoppinsRegular',
                            fontSize: 15,
                            color: Color(0xff8f9ba8)),
                      )),
                    ),
                  ),
                  SizedBox(
                    height: MediaQuery.of(context).size.height * 0.01,
                  ),
                ] +
                productList));
  }

  void showPendingUI() {
    setState(() {
      _purchasePending = true;
    });
  }

  void deliverProduct(PurchaseDetails purchaseDetails) async {
    // IMPORTANT!! Always verify purchase details before delivering the product.
    if (purchaseDetails.productID == _kConsumableId) {
      await ConsumableStore.save(purchaseDetails.purchaseID!);
      List<String> consumables = await ConsumableStore.load();
      setState(() {
        _purchasePending = false;
        _consumables = consumables;
      });
    } else {
      setState(() {
        _purchases.add(purchaseDetails);
        _purchasePending = false;
      });
    }
  }

  void handleError(IAPError error) {
    setState(() {
      _purchasePending = false;
    });
  }

  Future<bool> _verifyPurchase(PurchaseDetails purchaseDetails) {
    // IMPORTANT!! Always verify a purchase before delivering the product.
    // For the purpose of an example, we directly return true.
    return Future<bool>.value(true);
  }

  void _handleInvalidPurchase(PurchaseDetails purchaseDetails) {
    // handle invalid purchase here if  _verifyPurchase` failed.
  }

  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 ||
            purchaseDetails.status == PurchaseStatus.restored) {
          bool valid = await _verifyPurchase(purchaseDetails);
          if (valid) {
            deliverProduct(purchaseDetails);
          } else {
            _handleInvalidPurchase(purchaseDetails);
            return;
          }
        }
        if (Platform.isAndroid) {
          if (!_kAutoConsume && purchaseDetails.productID == _kConsumableId) {
            final InAppPurchaseAndroidPlatformAddition androidAddition =
                _inAppPurchase.getPlatformAddition<
                    InAppPurchaseAndroidPlatformAddition>();
            await androidAddition.consumePurchase(purchaseDetails);
          }
        }
        if (purchaseDetails.pendingCompletePurchase) {
          await _inAppPurchase.completePurchase(purchaseDetails);
        }
      }
    });
  }

  Future<void> confirmPriceChange(BuildContext context) async {
    if (Platform.isAndroid) {
      final InAppPurchaseAndroidPlatformAddition androidAddition =
          _inAppPurchase
              .getPlatformAddition<InAppPurchaseAndroidPlatformAddition>();
      var priceChangeConfirmationResult =
          await androidAddition.launchPriceChangeConfirmationFlow(
        sku: 'purchaseId',
      );
      if (priceChangeConfirmationResult.responseCode == BillingResponse.ok) {
        ScaffoldMessenger.of(context).showSnackBar(SnackBar(
          content: Text('Price change accepted'),
        ));
      } else {
        ScaffoldMessenger.of(context).showSnackBar(SnackBar(
          content: Text(
            priceChangeConfirmationResult.debugMessage ??
                "Price change failed with code ${priceChangeConfirmationResult.responseCode}",
          ),
        ));
      }
    }
    if (Platform.isIOS) {
      var iapIosPlatformAddition = _inAppPurchase
          .getPlatformAddition<InAppPurchaseIosPlatformAddition>();
      await iapIosPlatformAddition.showPriceConsentIfNeeded();
    }
  }

  GooglePlayPurchaseDetails? _getOldSubscription(
      ProductDetails productDetails, Map<String, PurchaseDetails> purchases) {
    GooglePlayPurchaseDetails? oldSubscription;
    if (productDetails.id == _kSilverSubscriptionId &&
        purchases[_kGoldSubscriptionId] != null) {
      oldSubscription =
          purchases[_kGoldSubscriptionId] as GooglePlayPurchaseDetails;
    } else if (productDetails.id == _kGoldSubscriptionId &&
        purchases[_kSilverSubscriptionId] != null) {
      oldSubscription =
          purchases[_kSilverSubscriptionId] as GooglePlayPurchaseDetails;
    }
    return oldSubscription;
  }
}

/// Example implementation of the
/// [`SKPaymentQueueDelegate`](https://developer.apple.com/documentation/storekit/skpaymentqueuedelegate?language=objc).
///
/// The payment queue delegate can be implementated to provide information
/// needed to complete transactions.
class ExamplePaymentQueueDelegate implements SKPaymentQueueDelegateWrapper {
  @override
  bool shouldContinueTransaction(
      SKPaymentTransactionWrapper transaction, SKStorefrontWrapper storefront) {
    return true;
  }

  @override
  bool shouldShowPriceConsent() {
    return false;
  }
}

class ConsumableStore {
  static const String _kPrefKey = 'consumables';
  static Future<void> _writes = Future.value();

  /// Adds a consumable with ID `id` to the store.
  ///
  /// The consumable is only added after the returned Future is complete.
  static Future<void> save(String id) {
    _writes = _writes.then((void _) => _doSave(id));
    return _writes;
  }

  /// Consumes a consumable with ID `id` from the store.
  ///
  /// The consumable was only consumed after the returned Future is complete.
  static Future<void> consume(String id) {
    _writes = _writes.then((void _) => _doConsume(id));
    return _writes;
  }

  /// Returns the list of consumables from the store.
  static Future<List<String>> load() async {
    return (await SharedPreferences.getInstance()).getStringList(_kPrefKey) ??
        [];
  }

  static Future<void> _doSave(String id) async {
    List<String> cached = await load();
    SharedPreferences prefs = await SharedPreferences.getInstance();
    cached.add(id);
    await prefs.setStringList(_kPrefKey, cached);
  }

  static Future<void> _doConsume(String id) async {
    List<String> cached = await load();
    SharedPreferences prefs = await SharedPreferences.getInstance();
    cached.remove(id);
    await prefs.setStringList(_kPrefKey, cached);
  }
}