jMonkeyEngine-wiki/docs/modules/ROOT/pages/jme3/advanced/nifty_gui_popup_menu.adoc

= Nifty GUI: Create a PopUp Menu
:author: 
:revnumber: 
:revdate: 2016/03/17 20:48
:relfileprefix: ../../
:imagesdir: ../..
ifdef::env-github,env-browser[:outfilesuffix: .adoc]


Even though you create and populate the popup menu in Java, you still need a “placeholder in your XML file.
The popup element needs to be placed _outside_ of any screen!

[source,xml]
----

<useControls filename="nifty-default-controls.xml"/>
...
<popup id="niftyPopupMenu" childLayout="absolute-inside"
       controller="ControllerOfYourChoice" width="10%">
  <interact onClick="closePopup()" onSecondaryClick="closePopup()" onTertiaryClick="closePopup()" />
  <control id="#menu" name="niftyMenu" />
</popup>
...
----

A brief explanation of some the attributes above:

*  The popup id is used within your Java code so that nifty knows which popup placeholder to create.
*  The Controller tells Nifty which Java class handles MenuItemActivatedEvent.
*  The on(Secondary/Tertiary)Click tells Nifty to close the popup if the user clicks anywhere except on the menu items (in this example; you have to define the closePopup()-method yourself, in the screen controller)
*  The control id is used by the Java class to define a control type (i.e. Menu)

The Java code within your defined ScreenController implementation:

[source,java]
----

private Element popup;
...
public void createMyPopupMenu(){
  popup = nifty.createPopup("niftyPopupMenu");
  Menu myMenu = popup.findNiftyControl("#menu", Menu.class);
  myMenu.setWidth(new SizeValue("100px")); // must be set
  myMenu.addMenuItem("Click me!", "menuItemIcon.png", 
    new menuItem("menuItemid", "blah blah")); // menuItem is a custom class
  nifty.subscribe(
    nifty.getCurrentScreen(), 
    myMenu.getId(), 
    MenuItemActivatedEvent.class, 
    new MenuItemActivatedEventSubscriber());
}

public void showMenu() { // the method to trigger the menu
  // If this is a menu that is going to be used many times, then
  // call this in your constructor rather than here   
  createMyPopupMenu() 
  // call the popup to screen of your choice:
  nifty.showPopup(nifty.getCurrentScreen(), popup.getId(), null); 
}

private class menuItem {
  public String id;
  public String name;
  public menuItem(String id, String name){
    this.id= id;
    this.name = name;
  }
}

----

*  The createMyPopupMenu() method creates the menu with set width so that you can populate it.
*  The showMenu() method is called by something to trigger the menu (i.e. could be a Key or some other method).
*  Note: if you want to be able to access the popup via your id, use createPopupWithId(id, id) instead.

To handle menu item events (i.e. calling a method when you click on a menu item), you register (subscribe) a EventTopicSubscriber&lt;MenuItemActivatedEvent&gt; class implementation to a nifty screen and element.

[source,java]
----

  private class MenuItemActivatedEventSubscriber 
    implements EventTopicSubscriber<MenuItemActivatedEvent> {
    
    @Override
    public void onEvent(final String id, final MenuItemActivatedEvent event) {
    	menuItem item = (menuItem) event.getItem();
       if ("menuItemid".equals(item.id)) {
		//do something !!!
       }
    }
  };

----