Google Play PurchaseService.BuyNative

GooglePlayPurchaseService.cs

protected async override Task<Receipt> BuyNative(Purchase purchase)
{
    var context = (Activity)Xamarin.Forms.Forms.Context;
    string developerPayload = Guid.NewGuid().ToString("N");
    var buyIntent = _connection.Service.GetBuyIntent(BillingConstants.ApiVersion, context.PackageName, purchase.Id, BillingConstants.ItemTypeInApp, developerPayload);

    int response = buyIntent.GetInt(BillingConstants.ResponseCode);
    if (response != BillingConstants.ResultOk)
    {
        //NOTE: see my full example for handling BillingConstants.ResultItemAlreadyOwned
        throw new Exception("GetBuyIntent failed, code: " + response);
    }

    var source =
        _purchaseSource = new TaskCompletionSource<Order>();
    var pendingIntent = (PendingIntent)buyIntent.GetParcelable(BillingConstants.BuyIntent);
    context.StartIntentSenderForResult(pendingIntent.IntentSender, BillingConstants.PurchaseRequestCode, new Intent(), 0, 0, 0);

    var order = await source.Task;
    if (order.DeveloperPayload != developerPayload)
    {
        throw new Exception($"DeveloperPayload did not match {developerPayload} != {order.DeveloperPayload}");
    }

    return await ConsumePurchase(order);
}

//NOTE: this is split out into a separate method for handling BillingConstants.ResultItemAlreadyOwned
private async Task<Receipt> ConsumePurchase(Order order)
{
    if (string.IsNullOrEmpty(order.PurchaseToken))
    {
        throw new Exception("PurchaseToken not found, cannot consume purchase!");
    }
    int response = await Task.Factory.StartNew(() => _connection.Service.ConsumePurchase(BillingConstants.ApiVersion, Application.Context.PackageName, order.PurchaseToken));
    if (response != BillingConstants.ResultOk)
    {
        throw new Exception("ConsumePurchase failed, code: " + response);
    }
    return new GoogleReceipt
    {
        Id = order.ProductId,
        TransactionId = order.OrderId ?? "TEST", //NOTE: if null, it is a test purchase
        PurchaseToken = order.PurchaseToken,
        DeveloperPayload = order.DeveloperPayload,
    };
}