@Override void onPurchasesUpdated(@BillingResponse int responseCode,
    List<Purchase> purchases) {
if (responseCode == BillingResponse.OK
        && purchases != null) {
    for (Purchase purchase : purchases) {
        handlePurchase(purchase);
    }
} else if (responseCode == BillingResponse.USER_CANCELED) {
    // Handle an error caused by a user canceling the purchase flow.
} else {
    // Handle any other error codes.
} }