BillingClient Lib：queryPurchaseHistoryAsync不拉测试购买

Question

您好，我正在使用BillingClient库开发应用程序内订阅。我无法在调试中看到成功购买的测试。没有在queryPurchaseHistoryAsync方法中填充productlist。这是正常现象吗？在启动连接方法期间是否必须满足什么条件？

billingClient.startConnection（

new BillingClientStateListener ()
{
     public void onBillingSetupFinished (into code)
     {

          if (code == BillingResponse.OK)
          {
            billingClient.queryPurchaseHistoryAsync (
                  SkuType.SUBS,
                   new PurchaseHistoryResponseListener ()
                   { 
                        public void onPurchaseHistoryReponse
                           (int code, List <Purchase> purchaselist)
                                { 
                                    /// purchaselist is always null
                                }
                   }
            )
          }
      }
 }

）