flash开发中如何实现界面代码分离

package 
{

	import flash.display.Sprite;
	import flash.display.DisplayObject;
	import flash.display.SimpleButton;
	import flash.events.MouseEvent;
	import flash.display.MovieClip;
	import flash.display.BitmapData;
	import flash.display.Bitmap;


	public class Demo extends MovieClip
	{
		[Embed(source = "skin.swf",symbol = "ButtonPause")]
		private var ButtonPause:Class;

		[Embed(source = "skin.swf",symbol = "ButtonPlay")]
		private var ButtonPlay:Class;

		[Embed(source = "skin.swf",symbol = "LogoImage")]
		private var LogoImage:Class;

		[Embed(source = "skin.swf",symbol = "TestMovie")]
		private var TestMovie:Class;


		public function Demo()
		{
			init();
		}

		private function init():void
		{
			var btnTest:SimpleButton = new ButtonPause() as SimpleButton;
			trace(btnTest,btnTest is SimpleButton);//Demo_ButtonPause0,true
			addChild(btnTest);
			btnTest.x = btnTest.y = 50;
			btnTest.addEventListener(MouseEvent.CLICK,btnTestClick);

			var btnTest2:SimpleButton = new ButtonPlay() as SimpleButton;
			trace(btnTest2);//Demo_ButtonPlay1
			addChild(btnTest2);
			btnTest2.y = 50;
			btnTest2.x = 100;
			btnTest2.addEventListener(MouseEvent.CLICK,btnTest2Click);


			var bmd:Bitmap = new LogoImage() as Bitmap;
			trace(bmd);//Demo_LogoImage2
			addChild(bmd);
			bmd.x = bmd.y = 200;

			var testMovie:MovieClip = new TestMovie() as MovieClip;
			addChild(testMovie);
			testMovie.x = testMovie.y = 180;
			trace(testMovie);//Demo_TestMovie3

		}

		private function btnTestClick(e:MouseEvent):void
		{
			trace("btnTest 被点击了!");
		}

		private function btnTest2Click(e:MouseEvent):void
		{
			trace("btnTest2 被点击了!");
		}
	}

}