验证购买的逻辑特定于你的应用。你应在验证之前检查内容是否已交付给用户。这是一种故障保护措施，可确保用户不会因因未知（可能是特定于设计的）问题而未交付的购买请求退款。
例如，如果您有一个产品可以删除广告，那么在验证之前，您应该检查该广告是否已被删除。
侦听器的示例代码：

void __updatePurchases(List<PurchaseDetails> data) async {

if (data.isNotEmpty) {
  // Add purchase data
  _purchases.addAll(data);

  // Handle any new purchases
  for (PurchaseDetails purchaseDetails in data) {
    if (purchaseDetails.status == PurchaseStatus.purchased ||
        purchaseDetails.status == PurchaseStatus.restored) {
      // Success, check delivery and complete purchase if purchase is not complete.
      if (purchaseDetails.pendingCompletePurchase && *your content delivery check here*) {
        _log.d("Completing purchase '${purchaseDetails.productID}'.");
        _iap.completePurchase(purchaseDetails);
      }
    } else if (purchaseDetails.status == PurchaseStatus.error) {
      // Failed, log error.
      _log.i("Purchase of '${purchaseDetails.productID}' failed.");
    }
  }

  // Query all products to get the details.
  ProductDetailsResponse response =
  await _iap.queryProductDetails(_availableProducts);

  _products = response.productDetails;

  // Notify listeners.
  notifyListeners();
}

} }