This page will introduce a technique with which you can handle an action which was performed on the given item stack. This is called an ActionHandler. Action handlers are functions that get called when a click on an ItemStackWrapper occurs.

Action handlers need to be registered at the construction of a menu object instance. For example:

public ExampleMenu(PlayerWrapper player, MenuConfiguration configuration) {  
  super(player, configuration, Locale.ENGLISH);  
  
  registerActionHandler("tnt", click -> {  
    topContainer().itemMap().remove(click.slot());  
    title("Hello, {viewer}");  
    build();  
    player().sendMessage("It simply works :)");  
    return CallResult.DENY_GRABBING;  
  });
}

This example removes the clicked item, changes the inventory title to "Hello, {viewer}" and sends a message to the player, that the click logic simply works.

The registerActionHandler method requires an unique identifier string and, of course, an ActionHandler instance. The string that was provided as the first argument is used in ItemStackWrappers to determine which action handler should be called when a click on an item occurs.

The action handler itself has only one method: the handle method. This method will be called if a click on any item was performed which has the name of the action handler configured to be called. The handle method's return type is an instance of CallResult.

CallResult is an enumeration which allows two different instances: DENY_GRABBING and ALLOW_GRABBING. However which one was returned, the player will be able to pick up the clicked item to hold it on the cursor. In common practice, only DENY_GRABBING is used.

The passed Click instance contains information about the click that was performed on the item stack. It contains the following information:

• clickType(): ClickType The type of click (Protocolize, click here for more information)
• clickedMenu(): Menu The clicked menu instance
• arguments(): List<String> A list of strings that have been passed by the item stack wrapper
• <T extends ItemStackWrapper> clickedItem(): T The instance of the clicked item stack wrapper
• slot(): int The clicked slot id