Flutter，in_app_purchase:显示订阅到期日期或状态的方法

dependencies:
  in_app_purchase: ^0.5.2

import 'package:in_app_purchase/in_app_purchase.dart';

final InAppPurchaseConnection _iap = InAppPurchaseConnection.instance;
final ProductDetailsResponse response = await _iap.queryProductDetails({'your_subscription_id'});
final ProductDetails product = response.productDetails.first;

final PurchaseDetails purchase = await _iap.queryPastPurchases();
if (purchase != null && purchase.status == PurchaseStatus.purchased) {
  final DateTime expirationDate = DateTime.fromMillisecondsSinceEpoch(purchase.transactionDate + product.subscriptionPeriod.numberOfUnits * 1000);
  final bool isExpired = expirationDate.isBefore(DateTime.now());
  
  if (isExpired) {
    print('订阅已过期');
  } else {
    print('订阅有效，到期日期：$expirationDate');
  }
} else {
  print('未购买订阅');
}