billingConnector = new BillingConnector(this, "license_key")
                .setConsumableIds(consumableIds)
                .setNonConsumableIds(nonConsumableIds)
                .setSubscriptionIds(subscriptionIds)
                .autoAcknowledge()
                .autoConsume()
                .enableLogging()
                .connect();

billingConnector.setBillingEventListener(new BillingEventListener() {
            @Override
            public void onProductsFetched(@NonNull List<SkuInfo> skuDetails) {
                /*Provides a list with fetched products*/
            }

            @Override
            public void onPurchasedProductsFetched(@NonNull List<PurchaseInfo> purchases) {
                /*Provides a list with fetched purchased products*/
            }

            @Override
            public void onProductsPurchased(@NonNull List<PurchaseInfo> purchases) {
                /*Callback after a product is purchased*/
            }

            @Override
            public void onPurchaseAcknowledged(@NonNull PurchaseInfo purchase) {
                /*Callback after a purchase is acknowledged*/
                
                /*
                 * Grant user entitlement for NON-CONSUMABLE products and SUBSCRIPTIONS here
                 *
                 * Even though onProductsPurchased is triggered when a purchase is successfully made
                 * there might be a problem along the way with the payment and the purchase won't be acknowledged
                 *
                 * Google will refund users purchases that aren't acknowledged in 3 days
                 *
                 * To ensure that all valid purchases are acknowledged the library will automatically
                 * check and acknowledge all unacknowledged products at the startup
                 * */
            }

            @Override
            public void onPurchaseConsumed(@NonNull PurchaseInfo purchase) {
                /*Callback after a purchase is consumed*/
                
                /*
                 * CONSUMABLE products entitlement can be granted either here or in onProductsPurchased
                 * */
            }

            @Override
            public void onBillingError(@NonNull BillingConnector billingConnector, @NonNull BillingResponse response) {
                /*Callback after an error occurs*/
                
                switch (response.getErrorType()) {
                    case CLIENT_NOT_READY:
                        //TODO - client is not ready yet
                        break;
                    case CLIENT_DISCONNECTED:
                        //TODO - client has disconnected
                        break;
                    case SKU_NOT_EXIST:
                        //TODO - sku does not exist
                        break;
                    case CONSUME_ERROR:
                        //TODO - error during consumption
                        break;
                    case ACKNOWLEDGE_ERROR:
                        //TODO - error during acknowledgment
                        break;
                    case ACKNOWLEDGE_WARNING:
                        /*
                         * This will be triggered when a purchase can not be acknowledged because the state is PENDING
                         * A purchase can be acknowledged only when the state is PURCHASED
                         *
                         * PENDING transactions usually occur when users choose cash as their form of payment
                         *
                         * Here users can be informed that it may take a while until the purchase complete
                         * and to come back later to receive their purchase
                         * */
                        //TODO - warning during acknowledgment
                        break;
                    case FETCH_PURCHASED_PRODUCTS_ERROR:
                        //TODO - error occurred while querying purchased products
                        break;
                    case BILLING_ERROR:
                        //TODO - error occurred during initialization / querying sku details
                        break;
                    case USER_CANCELED:
                        //TODO - user pressed back or canceled a dialog
                        break;
                    case SERVICE_UNAVAILABLE:
                        //TODO - network connection is down
                        break;
                    case BILLING_UNAVAILABLE:
                        //TODO - billing API version is not supported for the type requested
                        break;
                    case ITEM_UNAVAILABLE:
                        //TODO - requested product is not available for purchase
                        break;
                    case DEVELOPER_ERROR:
                        //TODO - invalid arguments provided to the API
                        break;
                    case ERROR:
                        //TODO - fatal error during the API action
                        break;
                    case ITEM_ALREADY_OWNED:
                        //TODO - failure to purchase since item is already owned
                        break;
                    case ITEM_NOT_OWNED:
                        //TODO - failure to consume since item is not owned
                        break;
                }
            }
        });

billingConnector.purchase(this, "sku_id");

billingConnector.subscribe(this, "sku_id");

billingConnector.unsubscribe(this, "sku_id");