如何在Flutter中首次购买应用内购买订阅？

dependencies:
  in_app_purchase: ^2.0.0

import 'package:in_app_purchase/in_app_purchase.dart';

class MyApp extends StatelessWidget {
  final InAppPurchaseConnection _iap = InAppPurchaseConnection.instance;

  @override
  Widget build(BuildContext context) {
    // 初始化in_app_purchase
    final bool available = await _iap.isAvailable();
    if (available) {
      // 连接到应用商店
      await _iap.connect();
    }
    // 其他代码...
  }
}

final ProductDetailsResponse response = await _iap.queryProductDetails(<String>[
  'your_product_id',
]);
if (response.notFoundIDs.isNotEmpty) {
  // 处理未找到的产品ID
}
final ProductDetails productDetails = response.productDetails.first;

Column(
  children: [
    Text(productDetails.title),
    Text(productDetails.description),
    Text(productDetails.price),
    RaisedButton(
      child: Text('购买'),
      onPressed: () async {
        final PurchaseParam purchaseParam = PurchaseParam(
          productDetails: productDetails,
          // 验证购买回调URL的方法，可以在购买成功后进行服务器验证
          // 如：urlLauncher.launchURL(purchaseDetails.verificationData.serverUrl);
        );
        if (await _iap.buyNonConsumable(purchaseParam: purchaseParam)) {
          // 处理购买成功的逻辑
        }
      },
    ),
  ],
)

StreamSubscription<List<PurchaseDetails>> _subscription;
_subscription = _iap.purchaseUpdatedStream.listen((List<PurchaseDetails> purchases) {
  for (PurchaseDetails purchase in purchases) {
    if (purchase.status == PurchaseStatus.purchased) {
      // 处理购买成功的逻辑
    } else if (purchase.status == PurchaseStatus.error) {
      // 处理购买失败的逻辑
    }
    // 确认或完成购买
    _iap.completePurchase(purchase);
  }
});

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