BillingHelper

Simplify the use of Google Play Billing Library (v7.0.0). Handles client connection, querying product details, owned purchases, different purchase types, acknowledging purchases, verify purchase signatures etc.

How does it work?

Make sure your Activity/Fragment implements BillingListener and initializes BillingHelper

class MainActivity: AppCompatActivity(), BillingListener {

    lateinit var billing: BillingHelper

    override fun onCreate(savedInstanceState: Bundle?, persistentState: PersistableBundle?) {
        super.onCreate(savedInstanceState, persistentState)

        // Construct helper - by default, connection will be initialized immediately with product 
        // details and owned purchases queried. All events are reported via billingListener.
        // At least one of productInAppPurchases or productSubscriptions is required.
        // For more configuration options, check BillingHelper constructor parameters.
        billing = BillingHelper(
            context = this, 
            productInAppPurchases = listOf("inAppPurchaseSkuName1", "inAppPurchaseSkuName2"),
            productSubscriptions = listOf("subscriptionSkuName"),
            billingListener = this
        )
    }

    override fun onDestroy() {
        super.onDestroy()
        // make sure to clean it up when you're done
        billing.endClientConnection()
    }

    override fun onBillingEvent(event: BillingEvent, message: String?) {
        // receive an event based on calls to billing
    }
}

Use any of its public methods or attributes, BillingHelper will do all the heavy lifting and always report changes via BillingListener

fun consumePurchase(purchase: Purchase)
fun endClientConnection()
fun getPurchaseForProductName(productName: String): Purchase?
fun getProductDetails(productName: String): ProductDetails?
fun isPurchased(productName: String): Boolean
fun launchPurchaseFlow(activity: Activity, productName: String)
fun initClientConnection(queryForProductDetailsOnConnected: Boolean, queryForOwnedPurchasesOnConected: Boolean)
fun initQueryOwnedPurchases()
fun initQueryProductDetails()
fun acknowledgePurchases(purchases: List<Purchase>)
fun isFeatureSupported(feature: String)
fun addBillingListener(listener: BillingListener)
fun removeBillingListener(listener: BillingListener)

var querySkuDetailsOnConnected: Boolean
var queryOwnedPurchasesOnConnected: Boolean
var autoAcknowledgePurchases: Boolean
var enableLogging: Boolean

var billingClient: BillingClient
    private set
val billingReady: Boolean
val connectionState: Int
var purchasesQueried: Boolean
    private set
var productDetailsQueried: Boolean
    private set
var isConnectionFailure: Boolean
    private set
val purchasesPresentable: Boolean

BillingEvent includes all of the things you might be interested in, served via BillingListener

enum class BillingEvent {
    BILLING_CONNECTED,
    BILLING_CONNECTION_FAILED,
    BILLING_DISCONNECTED,
    QUERY_PRODUCT_DETAILS_COMPLETE,
    QUERY_PRODUCT_DETAILS_FAILED,
    QUERY_OWNED_PURCHASES_COMPLETE,
    QUERY_OWNED_PURCHASES_FAILED,
    PURCHASE_COMPLETE,
    PURCHASE_FAILED,
    PURCHASE_CANCELLED,
    PURCHASE_ACKNOWLEDGE_SUCCESS,
    PURCHASE_ACKNOWLEDGE_FAILED,
    CONSUME_PURCHASE_SUCCESS,
    CONSUME_PURCHASE_FAILED
}

Best practices

Since library caches latest state of products and purchases as they are known to an instance based on the data requested, it's suggested to rely on a single instance of BillingHelper in your app.
Otherwise you may need to check for the latest information before using the purchased items or item details (manually handle the Optimistic Concurrency Control).

Great! How do I get started?

Make sure root build.gradle repositories include JitPack

allprojects {
    repositories {
        maven { url 'https://jitpack.io' }
    }
}

And BillingHelper dependency is added to app build.gradle

dependencies {
    implementation "com.github.mvojtkovszky:BillingHelper:$latest_version"
}