监测Image控件的图片来源发生变化时候的事件。

Image控件的sourceChanged事件。
示例：

代码：

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/06/27/detecting-when-the-source-changes-on-an-image-control-in-flex/ -->
<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>

通过AS实现：

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/06/27/detecting-when-the-source-changes-on-an-image-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white"
        initialize="init();">

    <mx:Script>
        <![CDATA[
            import mx.containers.ApplicationControlBar;
            import mx.controls.Alert;
            import mx.controls.Button;
            import mx.controls.Image;

            private var button1:Button;
            private var button2:Button;
            private var button3:Button;
            private var img:Image;

            private function init():void {
                button1 = new Button();
                button1.label = "Flash";
                button1.addEventListener(MouseEvent.CLICK, function():void {
                    img.source = "assets/fl_appicon.jpg";
                });

                button2 = new Button();
                button2.label = "Flash Player";
                button2.addEventListener(MouseEvent.CLICK, function():void {
                    img.source = "assets/fl_player_appicon.jpg";
                });

                button3 = new Button();
                button3.label = "Flex";
                button3.addEventListener(MouseEvent.CLICK, function():void {
                    img.source = "assets/fx_appicon.jpg";
                });

                var appControlBar:ApplicationControlBar = new ApplicationControlBar();
                appControlBar.dock = true;
                appControlBar.addChild(button1);
                appControlBar.addChild(button2);
                appControlBar.addChild(button3);
                Application.application.addChildAt(appControlBar, 0);

                img = new Image();
                img.source = "assets/fx_appicon.jpg";
                img.width = 100;
                img.height = 100;
                img.addEventListener("sourceChanged", image_sourceChanged);
                addChild(img);
            }

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

</mx:Application>