User Guide

ManualsBrandsMacromedia ManualsOtherFLASH MX 2004-USING ACTIONSCRIPT IN FLASH

100

94 Chapter 3: Using Best Practices

Using listener syntax

There are several ways to write listeners for events in Flash MX 2004. Some popular techniques

are shown in the following code examples. The first example shows a properly formatted listener

syntax, which uses a Loader component to load content into a SWF file. The

progress event

starts when content loads, and the

complete event indicates when loading finishes.

var box_ldr:mx.controls.Loader;

var ldrListener:Object = new Object();

ldrListener.progress = function(evt:Object) {

trace("loader loading:"+Math.round(evt.target.percentLoaded)+"%");

};

ldrListener.complete = function(evt:Object) {

trace("loader complete:"+evt.target._name);

};

box_ldr.addEventListener("progress", ldrListener);

box_ldr.addEventListener("complete", ldrListener);

box_ldr.load("http://www.macromedia.com/images/shared/product_boxes/159x120/15

9x120_box_flashpro.jpg");

The following example shows another recommended way of using a listener. In this example, you

define a function that is called when the user presses a Button component instance on the Stage:

var submit_button:mx.controls.Button;

submit_button.clickHandler = function(evt:Object) {

trace(evt.target._name);

}

By appending Handler to the event name (in this case, click), the event is caught, and you trace

an instance name when a user clicks the button.

A slight variation on the first example in this section is to use the

handleEvent method, but this

technique is slightly more cumbersome. It is not recommended, because you must use a series of

if..else statements or a switch statement to detect what event is caught.

var box_ldr:mx.controls.Loader;

var ldrListener:Object = new Object();

ldrListener.handleEvent = function(evt:Object) {

switch (evt.type) {

case 'progress' :