public void launchPurchaseFlow(Activity act, String sku, String itemType, int requestCode,
                        OnIabPurchaseFinishedListener listener, String extraData) {
        checkNotDisposed();
        checkSetupDone("launchPurchaseFlow");
        flagStartAsync("launchPurchaseFlow");
        IabResult result;

        if (itemType.equals(ITEM_TYPE_SUBS) && !mSubscriptionsSupported) {
            IabResult r = new IabResult(IABHELPER_SUBSCRIPTIONS_NOT_AVAILABLE,
                    "Subscriptions are not available.");
            flagEndAsync();
            if (listener != null) listener.onIabPurchaseFinished(r, null);
            return;
        }

        try {
            logDebug("Constructing buy intent for " + sku + ", item type: " + itemType);
            Bundle buyIntentBundle = mService.getBuyIntent(3, mContext.getPackageName(), sku, itemType, extraData);
            int response = getResponseCodeFromBundle(buyIntentBundle);
            if (response != BILLING_RESPONSE_RESULT_OK) {
                logError("Unable to buy item, Error response: " + getResponseDesc(response));
                flagEndAsync();
                result = new IabResult(response, "Unable to buy item");
                if (listener != null) listener.onIabPurchaseFinished(result, null);
                return;
            }

            PendingIntent pendingIntent = buyIntentBundle.getParcelable(RESPONSE_BUY_INTENT);
            logDebug("Launching buy intent for " + sku + ". Request code: " + requestCode);
            mRequestCode = requestCode;
            mPurchaseListener = listener;
            mPurchasingItemType = itemType;
            act.startIntentSenderForResult(pendingIntent.getIntentSender(),
                                           requestCode, new Intent(),
                                           Integer.valueOf(0), Integer.valueOf(0),
                                           Integer.valueOf(0));
        }
        catch (SendIntentException e) {
            logError("SendIntentException while launching purchase flow for sku " + sku);
            e.printStackTrace();
            flagEndAsync();

            result = new IabResult(IABHELPER_SEND_INTENT_FAILED, "Failed to send intent.");
            if (listener != null) listener.onIabPurchaseFinished(result, null);
        }
        catch (RemoteException e) {
            logError("RemoteException while launching purchase flow for sku " + sku);
            e.printStackTrace();
            flagEndAsync();

            result = new IabResult(IABHELPER_REMOTE_EXCEPTION, "Remote exception while starting purchase flow");
            if (listener != null) listener.onIabPurchaseFinished(result, null);
        }
    }