User Guide

194 Chapter 6: Components Dictionary

The second usage example uses a dispatcher/listener event model. A component instance

(

comboBoxInstance) dispatches an event (in this case, enter) and the event is handled by a

function, also called a handler, on a listener object (

listenerObject) that you create. You define

a method with the same name as the event on the listener object; the method is called when the

event is triggered. When the event is triggered, it automatically passes an event object

(

eventObject) to the listener object method. Each event object has properties that contain

information about the event. You can use these properties to write code that handles the event.

Finally, you call the

addEventListener() method on the component instance that broadcasts

the event to register the listener with the instance. When the instance dispatches the event, the

listener is called.

For more information, see “EventDispatcher class” on page 415.

Example

The following example sends a message to the Output panel when the drop-down list begins

to close:

form.enter = function(){

trace("The combo box enter event was triggered");

}

myCombo.addEventListener("enter", form);