Flex中利用sourceChanged事件检测图片(image)控件的图片源(source属性)是否改变的例子

让我们先来看一下Demo（

）：

下面是完整代码(或点击这里察看)：
Download: main.mxml

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
layout="vertical"
verticalAlign="middle"
backgroundColor="white">

<mx:Script>
<![CDATA[
import mx.controls.Alert;

private function init():void {
img.addEventListener("sourceChanged", image_sourceChanged);
}

private function image_sourceChanged(evt:Event):void {
Alert.show(evt.toString(), evt.type);
}
]]>
</mx:Script>

<mx:ApplicationControlBar dock="true">
<mx:Button label="Flash"
click="img.source = 'assets/fl_appicon.jpg';" />
<mx:Button label="Flash Player"
click="img.source = 'assets/fl_player_appicon.jpg';" />
<mx:Button label="Flex"
click="img.source = 'assets/fx_appicon.jpg';" />
</mx:ApplicationControlBar>

<mx:Image id="img"
source="assets/fx_appicon.jpg"
initialize="init();"
width="100"
height="100" />

</mx:Application>