Making a Fake GUI and Restricting Player Use

I'm trying to make a "Shop" with a fake inventory screen, I know how to create the inventory, add an item, and display it to the player. But currently a player can take the items out of the inventory, and reopen the inventory, effectively duping them. I want to restrict the player from moving ANYTHING in their or the shop's inventory while it is open, besides click on it. How do i do this? Here is the code that I tried to do:

Code:java

 @EventHandler
    public void onPlayerInteract(PlayerInteractEvent event) {
        inventory = event.getPlayer().getServer().createInventory(null, 18, "ECShop");
        ItemStack item1 = new ItemStack(57, 1);
        inventory.addItem(item1);
        Player player = event.getPlayer();
        Action action = event.getAction();
        if (action == Action.RIGHT_CLICK_AIR || action == Action.RIGHT_CLICK_BLOCK && player.getItemInHand().getType() == Material.WRITTEN_BOOK) {
 
            BookMeta meta = (BookMeta) player.getItemInHand().getItemMeta();
            if (meta.getTitle().equals(ChatColor.GREEN + "ECShop")) {
 
                player.sendMessage("Coming soon!");
                player.closeInventory();
                player.openInventory(inventory);
 
            }
 
 
        }
    }
 
    @EventHandler
    public void onInventoryClickEvent(InventoryClickEvent event) {
        if (event.getInventory().equals("inventory")) {
            if(event.getCurrentItem().getType() == Material.DIAMOND_BLOCK){
                event.setCancelled(true);
            }
 
        }
 
    }

Any help?

 

Without actually reading your source (I know terrible), I would suggest cancelling the event (InventoryClickEvent).

Be aware, there are ways to get round this which can cause duplication glitches left, centre and right.

EDIT: And I read your source, oh snap I'm a fool.

So what's the problem? Does it not stop you from taking out the diamond block?