User Guide

1344 UIComponent class

Description

Event; notifies listeners that the object has received keyboard focus.

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

(

componentInstance) dispatches an event (in this case, focusIn), 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

EventDispatcher.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 499.

The second usage example uses an

on() handler and must be attached directly to a

component instance.

Example

The following code disables a Button component, btn, while a user types the TextInput

component,

txt, and enables the button when the user clicks it:

var txt:mx.controls.TextInput;

var btn:mx.controls.Button;

var txtListener:Object = new Object();

txtListener.focusOut = function() {

_root.btn.enabled = true;

}

txt.addEventListener("focusOut", txtListener);

var txtListener2:Object = new Object();

txtListener2.focusIn = function() {

_root.btn.enabled = false;

}

txt.addEventListener("focusIn", txtListener2);