Add Callback when purchase 

  fun setBillingListener(listener: IKNewBillingHandlerListener)
Example 
  ikBilling.setBillingListener(
    listener = object : IKNewBillingHandlerListener {
        override fun onBillingError(error: IKBillingError) {

        }

        override fun onBillingInitialized() {

        }

        override fun onProductPurchased(
            productId: String,
            orderId: String?,
            purchaseToken: String?
        ) {

        }

        override fun onPurchaseHistoryRestored() {

        }
    }
)
  
  ikBilling.setBillingListener(new IKNewBillingHandlerListener() {
    @Override
    public void onProductPurchased(@NonNull String s, @Nullable String s1, @Nullable String s2) {
        
    }

    @Override
    public void onPurchaseHistoryRestored() {

    }

    @Override
    public void onBillingError(@NonNull IKBillingError ikBillingError) {

    }

    @Override
    public void onBillingInitialized() {

    }

    @Override
    public void onBillingDataSave(boolean b) {

    }
});

Best practice

Because onBillingDataSave delay about 5s, so when you need to check immediately it will not work now. You can pre save an variable cho check realtime.

  var isPurchaseNow = false
ikBilling.setBillingListener(
    listener = object : IKNewBillingHandlerListener {
        override fun onBillingError(error: IKBillingError) {

        }

        override fun onBillingInitialized() {

        }

        override fun onProductPurchased(
            productId: String,
            orderId: String?,
            purchaseToken: String?
        ) {
            isPurchaseNow = true
        }

        override fun onPurchaseHistoryRestored() {

        }
    }
)

val checkIAP = isPurchaseNow || ikBilling.isIabServiceAvailable(this)

One-time Purchase Package (Lifetime Purchase) 

  fun purchase(
  activity: Activity?,
  productId: String,
  listener: IKBillingPurchaseListener? = null
)

Parameters:

  • activity: The activity context used to initiate the purchase flow. This is necessary for displaying the purchase dialog to the user.

  • productId: String: The ID of the product you want to retrieve details for. This is typically defined in the Google Play Console as part of your in-app products or subscriptions.

  • callback: IKBillingPurchaseListener - Handles callbacks related to the purchase process, including successful purchases, failed transactions, and products already purchased.

Example 
  ikBilling.purchase(
    activity = this,
    productId = "android.test.purchased",
    listener = object : IKBillingPurchaseListener {
        override fun onBillingFail(productId: String, error: IKBillingError) {

        }

        override fun onBillingSuccess(productId: String) {

        }

        override fun onProductAlreadyPurchased(productId: String) {

        }

    }
)
  
  ikBilling.purchase(
        this,
        "android.test.purchased",
        new IKBillingPurchaseListener() {
            @Override
            public void onProductAlreadyPurchased(@NonNull String s) {
                
            }

            @Override
            public void onBillingSuccess(@NonNull String s) {

            }

            @Override
            public void onBillingFail(@NonNull String s, @NonNull IKBillingError ikBillingError) {

            }
        }
);

Multi-purchase Package (Buy multiple times, recharge, etc.) 

  fun purchase(
  activity: Activity?,
  productId: String,
  listener: IKBillingPurchaseListener? = null,
  hasBuyMultipleTime: Boolean
)

Parameters:

  • activity: The activity context used to initiate the purchase flow. This is necessary for displaying the purchase dialog to the user.

  • productId: String: The ID of the product you want to retrieve details for. This is typically defined in the Google Play Console as part of your in-app products or subscriptions.

  • callback: IKBillingPurchaseListener - Handles callbacks related to the purchase process, including successful purchases, failed transactions, and products already purchased.

  • hasBuyMultipleTime: Indicates whether the user is allowed to purchase the same product multiple times.

Example 
  if (!ikBilling.isIabServiceAvailable(this)) {
    // Google Play Services is not available
    return
}
ikBilling.purchase(
    activity = this,
    productId = "android.test.purchased",
    listener = object :
        IKBillingPurchaseListener {
        override fun onProductAlreadyPurchased(productId: String) {

        }

        override fun onBillingFail(productId: String, error: IKBillingError) {

        }

        override fun onBillingSuccess(productId: String) {

        }
    }, true
)
  
   if (!ikBilling.isIabServiceAvailable(this)) {
    // Google Play Services is not available
    return;
}
ikBilling.purchase(this, "android.test.purchased", new IKBillingPurchaseListener() {
    @Override
    public void onProductAlreadyPurchased(@NonNull String s) {

    }

    @Override
    public void onBillingSuccess(@NonNull String s) {

    }

    @Override
    public void onBillingFail(@NonNull String s, @NonNull IKBillingError ikBillingError) {

    }
}, true);

Subscription 

  fun subscribe(
  activity: Activity?,
  productId: String,
  listener: IKBillingPurchaseListener? = null
)

Parameters:

  • activity: The activity context used to initiate the purchase flow. This is necessary for displaying the purchase dialog to the user.

  • productId: String: The ID of the product you want to retrieve details for. This is typically defined in the Google Play Console as part of your in-app products or subscriptions.

  • callback: IKBillingPurchaseListener - Handles callbacks related to the purchase process, including successful purchases, failed transactions, and products already purchased.

Example 
  if (!ikBilling.isIabServiceAvailable(this)) {
    // Google Play Services is not available
    return
}
ikBilling.subscribe(this, "android.test.purchased", object :
    IKBillingPurchaseListener {
    override fun onProductAlreadyPurchased(productId: String) {

    }

    override fun onBillingFail(productId: String, error: IKBillingError) {

    }

    override fun onBillingSuccess(productId: String) {

    }
})
  
   if (!ikBilling.isIabServiceAvailable(this)) {
    // Google Play Services is not available
    return;
}
ikBilling.subscribe(this, "android.test.purchased", new IKBillingPurchaseListener() {
    @Override
    public void onProductAlreadyPurchased(@NonNull String s) {

    }

    @Override
    public void onBillingSuccess(@NonNull String s) {

    }

    @Override
    public void onBillingFail(@NonNull String s, @NonNull IKBillingError ikBillingError) {

    }
});

Update an existing subscription with a new package

This function facilitates updating an existing subscription by allowing users to switch from their current subscription (oldProductId) to a new subscription (productId). This is particularly useful for handling subscription upgrades or downgrades.

  fun updateSubscription(
  activity: Activity?,
  oldProductId: String,
  productId: String,
  listener: IKBillingPurchaseListener? = null
)

Parameters:

  • activity: The activity context used to initiate the purchase flow. This is necessary for displaying the purchase dialog to the user.

  • oldProductId: The product ID of the current subscription that the user is upgrading from or downgrading from.

  • productId: The product ID of the new subscription that the user is switching to.

  • callback: IKBillingPurchaseListener - Handles callbacks related to the purchase process, including successful purchases, failed transactions, and products already purchased.