How to load a SWF compiled by Flex into a SWF compiled by Flash CS4

I compiled a simple AS3 project 开发者_开发百科using Flex 3.5 (also tried Flex 4.1) to create a small swf which draws a simple red square on screen. Nothing too complex that requires special flashplayer support (see code below)

package  
{
    import flash.display.Sprite;

    /**
     * @author John Lindquist
     */
    [SWF(width="1024", height="768", frameRate="24")]
    public class EasingATimeline extends Sprite 
    {
        private var square:Sprite;
        private static const STEP_DURATION:Number = 1;

        public function EasingATimeline()
        {
            square = new Sprite();  
            square.graphics.beginFill(0xcc0000);
            square.graphics.drawRect(0, 0, 50, 50);
            square.graphics.endFill();

            square.x = 100;
            square.y = 50;

            addChild(square);
        }
    }
}

and tried to load it into a AS2 swf I have compiled using Flash CS4. But that just didn't work. I don't get any errors when loading and the AS2 swf can load any swf, either compiled in AS2 or AS3 by Flash.

Any ideas?

Flex/Flash builder is only for as3. So you can't load it into an as2 swf. You can however create a new as3 file in flash and load both your as2 swf and your flex swf and position them accordingly. Loading swfs is easy in as3:

var as2:Loader = new Loader();
as2.load(new URLRequest("myAS2Thing.swf"));
as2.addEventListener(Event.COMPLETE, onDoneLoadingAS2);
function onDoneLoadingAS2(e:Event):void{
 as2.x = 100;
 as2.y = 100;
  addChild(as2);
}