/// <summary> /// If you use the Google Play Billing Library version 2.0 or newer, you must acknowledge all purchases within three days. /// </summary> /// <param name="purchase"></param> /// <returns></returns> private async Task <bool> NotifyFullFillmentAsync(Purchase purchase) { if (!purchase.IsAcknowledged) { if (BillingClient == null || !BillingClient.IsReady) { await ConnectAsync(); } _tcsAcknowledge = new TaskCompletionSource <bool>(); AcknowledgePurchaseParams acknowledgePurchaseParams = AcknowledgePurchaseParams.NewBuilder() .SetPurchaseToken(purchase.PurchaseToken) .Build(); BillingClient.AcknowledgePurchase(acknowledgePurchaseParams, this); return(await _tcsAcknowledge?.Task); } return(true); }