In-App Billing Plugin for Xamarin and Windows

A simple In-App Purchase plugin for Xamarin and Windows to query item information, purchase items, restore items, and more.

Documentation

Get started by reading through the In-App Billing Plugin documentation.

There are changes in version 4.0 so read below.

Source code reference -> https://github.com/jamesmontemagno/app-ac-islandtracker/blob/freemium/TurnipTracker/ViewModel/ProViewModel.cs

NuGet

• NuGet: Plugin.InAppBilling

Platform Support

Platform	Version
Xamarin.iOS	iOS 8+
tvOS - Apple TV	All
Xamarin.Android	API 14+
Windows 10 UWP	10+

Created By: @JamesMontemagno

• Twitter: @JamesMontemagno
• Blog: Montemagno.com
• Podcasts: Merge Conflict, Coffeehouse Blunders, The Xamarin Podcast
• Video: The Xamarin Show on Channel 9, YouTube Channel

Checkout my podcast on IAP

I co-host a weekly development podcast, Merge Conflict, about technology and recently covered IAP and this library: Merge Conflict 28: Demystifying In-App Purchases

Version 4 Major Update - Android

We now use Xamarin.Essentials for getting access to the current activity. So ensure you initialize Xamarin.Essentials in your Android app.

Also if you get a null exception the linker is being aggressive so write the following code in your MainActivity:

var context = Xamarin.Essentials.Platform.AppContext;
var activity = Xamarin.Essentials.Platform.CurrentActivity;

Version 4.X updates to the new Android billing client. This means there are few important changes:

1. You must acknowledge all purchases within 3 days, by calling AcknowledgePurchaseAsync or the Consume API if it a consumable.
2. You must hanle Pending Transactions from outside of you app. See docs from Google
3. HandleActivityResult is removed from the API as it is not needed

Upgrading from 2/3 to 4

• Remove Plugin.CurrentActivity.CrossCurrentActivity.Current.Activity = this;
• Remove InAppBillingImplementation.HandleActivityResult(requestCode, resultCode, data);
• Change: await CrossInAppBilling.Current.ConnectAsync(ItemType.InAppPurchase); to await CrossInAppBilling.Current.ConnectAsync();
• Change: CrossInAppBilling.Current.PurchaseAsync(productId, ItemType.InAppPurchase, payload); to CrossInAppBilling.Current.PurchaseAsync(productId, ItemType.InAppPurchase);

Pending Transactions:

• If the result of PurchaseAsync is PurchaseState.PaymentPending, store the order details locally and inform the user that they will have access to the product when the payment completes
• When the user starts the app (and/or visits a particular page), if the stored PurchaseState is PaymentPending, call GetPurchasesAsync and query the result for a purchase that matches the stored purchase.
• If the PurchaseState for this purchase is still PaymentPending, show the same no-access message
• If the PurchaseState is Purchased, call ConsumePurchaseAsync or AcknowledgePurchaseAsync, depending on the product type

To respond to pending transactions you can subscribe to a listener in your Android project startup:

// Connect to the service here
await CrossInAppBilling.Current.ConnectAsync();

// Check if there are pending orders, if so then subscribe
var purchases = await CrossInAppBilling.Current.GetPurchasesAsync(ItemType.InAppPurchase);

if (purchases?.Any(p => p.State == PurchaseState.PaymentPending) ?? false)
{
  Plugin.InAppBilling.InAppBillingImplementation.OnAndroidPurchasesUpdated = (billingResult, purchases) =>
  {
       // decide what you are going to do here with purchases
       // probably acknowledge
       // probably disconnect
  };
}
else
{
  await CrossInAppBilling.Current.DisconnectAsync();
}

If you do connect the IsConnected propety will be true and when you make purchases or check purchases again you should check ahead of time and not re-connect or disconnect if there are pending purchases

I highly recommend reading the entire Google Play Billing System docs.

Consumable vs Non-consumables on Android

On Android if you purchase anything you must first Acknowledge a purchase else it will be refunded. See the android documentation.

https://developer.android.com/google/play/billing/integrate#process https://developer.android.com/google/play/billing/integrate#pending

For consumables, the consumeAsync() method fulfills the acknowledgement requirement and indicates that your app has granted entitlement to the user. This method also enables your app to make the one-time product available for purchase again.

So, if you have a consumable... ConsumePurchaseAsync will also acknowledge it, if you have a non-consumable you will need to call AcknowledgePurchaseAsync.

Version 4+ Linker Settings

For linking if you are setting Link All you may need to add:

Android:

Plugin.InAppBilling;Xamarin.Android.Google.BillingClient

iOS:

--linkskip=Plugin.InAppBilling

License

The MIT License (MIT), see LICENSE file.

Want To Support This Project?

All I have ever asked is to be active by submitting bugs, features, and sending those pull requests down! Want to go further? Make sure to subscribe to my weekly development podcast Merge Conflict, where I talk all about awesome Xamarin goodies and you can optionally support the show by becoming a supporter on Patreon.