1.0.0 (May 12, 2017)
May 9, 2017
Oct 4, 2019 (Retired)
Stephen Vinouze (StephenVinouze)
Stephen Vinouze (StephenVinouze)
Source code


Gradle Dependency

Add this in your root build.gradle file:

allprojects {
 repositories {
  // ... other repositories
  maven { url "" }

Then add the following dependency in your project.

dependencies {
  compile "com.github.StephenVinouze:KinApp:{latest_version}"

⚠️ Do not forget to enable coroutines in your project as this library needs them

Configuring your InApp Purchase

Before integrating this library to manage your IAP, you probably must have already configured your application to integrate some products that you want your end users to buy. Understanding how this is done is rather well documented, but can be quite confusing as to how it really works. In addition to this library, I redacted an article on Medium that describes a complete workflow to properly configure your IAP step by step.

Getting started

In your AndroidManifest.xml file, add the following line if your manifest merger is disabled :

 <uses-permission android:name="" />

You will need a developer payload that can be found in your Google Developer Console from your already set up application. This id is uniquely attached to this application and will refer to your InApp products that you will declare.

In your calling Activity, instanciate the KinAppManager by adding the following lines :

private val billingManager = KinAppManager(this, "<YOUR_DEVELOPER_PAYLOAD_HERE>")

override fun onCreate(savedInstanceState: Bundle?) {

override fun onDestroy() {

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    if (!billingManager.verifyPurchase(requestCode, resultCode, data)) {
        super.onActivityResult(requestCode, resultCode, data)

Then implement the KinAppListener interface :

override fun onBillingReady() {
    // From this point you can use the Manager to fetch/purchase/consume/restore items

override fun onPurchaseFinished(purchaseResult: KinAppPurchaseResult, purchase: KinAppPurchase?) {
    // Handle your purchase result here
    when (purchaseResult) {
        KinAppPurchaseResult.SUCCESS -> {
            // Purchase successful with a non-null KinAppPurchase object.
            // You may choose to consume this item right now if you want to be able to re-buy it
        KinAppPurchaseResult.ALREADY_OWNED -> {
            // You already own this item. If you need to buy it again, consider consuming it first (you may need to restore your purchases before that)
        KinAppPurchaseResult.INVALID_PURCHASE -> {
            // Purchase invalid and cannot be processed
        KinAppPurchaseResult.INVALID_SIGNATURE -> {
            // Marked as success from the Google Store but signature detected as invalid and should not be processed
        KinAppPurchaseResult.CANCEL -> {
            // Manual cancel from the user

Basic usage

Once your KinAppManager is configured, you can use the various features offered by this library. Be advised that the library uses the experimental Kotlin coroutines to elegantly handle asynchronous requests in order to avoid blocking the main thread. You can refer to the sample application if you need some help.

Fetching products

As soon as you have configured your application on the Developer console and added some InApp products, you can retrieve them in your application ( ⚠️ Suspend call) :

launch(UI) {
 val products = billingManager.fetchProductsAsync(<your_products_id_here>, KinAppProductType.INAPP).await()

You can specify the nature of the product you want to fetch. It can be either of type INAPP or SUBSCRIPTION. This call is marked as suspend as it needs to be run asynchronously without blocking the main thread.

Purchase product

Purchasing a product can be done using a product_id and by specifying the calling activity. This is mandatory in order to be called back in the onActivityResult method. Finally, same as fetching product, just specify the nature oy your product :

billingManager.purchase(this, <your_products_id_here>, KinAppProductType.INAPP)

Consuming product

This part is only relevant to INAPP product types. A InApp product can be either consumable or one-time-purchase type. When you purchase an item, you own it. Unless you decide to consume it, you won't be able to re-purchase this item. This is important to understand this and distinguish between the two types of InApp products. You can consume an item by using these lines ( ⚠️ Suspend call) :

launch(UI) {
 val success = billingManager.consumePurchaseAsync(<your_purchase_object>).await()

Restoring purchases

Finally, you must be able to handle purchase restoration in your application. This can be easily done using these lines :

val purchases = billingManager.restorePurchases(KinAppProductType.INAPP)

Note that this will only bring you all the purchases you own.


This library should be able to manage subscription and was designed that way. However, no subscription were made while developing this library hence cannot be marked as fully supported. Any test/review/PR is welcomed to fully support this ;)

Testing InApp purchase

You can use the static responses provided by Google to test the basic cases and ensure your application is correctly responding even before adding any products to your Developer Console. Just use this :

billingManager.purchase(this, KinAppManager.TEST_PURCHASE_SUCCESS, KinAppProductType.INAPP)

This will present to you a test product dialog that always succeed. You can try the other static responses :


Pull requests

I welcome and encourage all pull requests. I might not be able to respond as fast as I would want to but I endeavor to be as responsive as possible.

All PR must:

  1. Be written in Kotlin
  2. Maintain code style
  3. Indicate whether it is a enhancement, bug fix or anything else
  4. Provide a clear description of what your PR brings
  5. Enjoy coding in Kotlin :)