Перенести код в другой класс.

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На коленке:

// интерфейс
package  
{
	public interface IMoveObject {
 
		function xMove(i:int):void;
		function yMove(i:int):void;
 
		function set speed (value:Number):void ;
		function get speed ( ):Number ;
	}
}
 
// Hero
package  
{
	import flash.display.Sprite;
 
	public class Hero extends Sprite implements IMoveObject
	{
		private var _speed:int;
 
		public function Hero ( ) {
			graphics.beginFill(0xFF8040);
			graphics.drawCircle(0, 0, 20);
			graphics.endFill( );
		}
 
		/* INTERFACE IMoveObject */
 
		public function xMove(i:int):void { x += i; }
		public function yMove(i:int):void { y += i; }
 
		public function set speed(value:Number):void { _speed = value; }
		public function get speed( ):Number { return _speed; }
	}
}
 
// controller
package  
{
	import flash.display.Stage;
	import flash.events.KeyboardEvent;
	import flash.events.TimerEvent;
	import flash.utils.Timer;
 
	public class Controller
	{
		private var object:IMoveObject;
		private var timer:Timer;
		private var stage:Stage;
 
		private const LEFT:int = 37;
		private const TOP:int = 38;
		private const RIGHT:int = 39;
		private const BOTTOM:int = 40;
 
		private var moveLeft:Boolean;
		private var moveTop:Boolean;
		private var moveRight:Boolean;
		private var moveBottom:Boolean;
 
 
 
		public function Controller (stage:Stage, object:IMoveObject) {
			this.object = object;
			this.stage = stage;
			timer = new Timer(10);
		}
 
 
 
		private function onTimerEvent(e:TimerEvent):void {
			if (moveLeft) object.xMove(-object.speed);
			if (moveRight) object.xMove(object.speed);
			if (moveTop) object.yMove(-object.speed);
			if (moveBottom) object.yMove(object.speed);
		}
 
 
 
		private function onKeyUp(e:KeyboardEvent):void {
			switch(e.keyCode) {
				case LEFT: moveLeft = false; break;
				case TOP: moveTop = false; break;
				case RIGHT: moveRight = false; break;
				case BOTTOM: moveBottom = false; break;
				default : return;
			}
		}
 
 
 
		private function onKeyDown(e:KeyboardEvent):void {
			switch(e.keyCode) {
				case LEFT: moveLeft = true; break;
				case TOP: moveTop = true; break;
				case RIGHT: moveRight = true; break;
				case BOTTOM: moveBottom = true; break;
				default : return;
			}
		}
 
 
 
		public function set interactiv (value:Boolean):void { 
			if (value) {
				timer.addEventListener(TimerEvent.TIMER, onTimerEvent);
				stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyDown);
				stage.addEventListener(KeyboardEvent.KEY_UP, onKeyUp);
				timer.start( );
			} else {
				timer.stop( );
				timer.removeEventListener(TimerEvent.TIMER, onTimerEvent);
				stage.removeEventListener(KeyboardEvent.KEY_DOWN, onKeyDown);
				stage.removeEventListener(KeyboardEvent.KEY_UP, onKeyUp);
			}
		}
	}
}
 
// Main
package  
{
	import flash.display.Sprite;
 
	public class Test2D extends Sprite 
	{
 
		public function Test2D ( ) {
 
			var hero:Hero = new Hero( );
				hero.speed = 10;
				hero.x = 100;
				hero.y = 100;
			addChild(hero);
 
			var control:Controller = new Controller(stage, hero);
				control.interactiv = true;
		}
	}
}