Mod fatal error

Your code is beautiful.

I found fatal error. 

[ Integer.valueOf(json.getInt(BillingManager.RESPONSE_CODE) ]

Not value JSON


 public Pair<Integer, List<Order>> queryPurchasedProducts() throws IllegalStateException, RemoteException {
    return this.queryPurchased(BillingManager.PURCHASE_TYPE_SUBSCRIPTION, null);
 }

Not subscription