问只有当按下左边的按钮时，玩家才会向左移动而不停止。

EN

    package  
{
import flash.display.MovieClip;
import flash.events.Event;
import flash.events.KeyboardEvent;
import flash.events.MouseEvent;
/**
 * ...
 * @author Moynul Hussain
 */
public class main extends MovieClip
{
    //MainMenu

    //background
    public var back:MovieClip;

    public var leftPressed:Boolean = false;
    public var rightPressed:Boolean = false;
    public var upPressed:Boolean = false;
    public var downPressed:Boolean = false;

    public var xScrollSpeed:int = 10;
    public var yScrollSpeed:int = 10;



    public var mcPlayButton:MovieClip;

    public function main() 
    {


    stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownHandler);
    stage.addEventListener(KeyboardEvent.KEY_UP, keyUpHandler);
    stage.addEventListener(Event.ENTER_FRAME, loop);


    }

    private function loop(e:Event):void 
    {
        if (leftPressed)
        {
            back.x += xScrollSpeed;
        } 
        else if (rightPressed)
        {
            back.x -= xScrollSpeed;
        }

        if (upPressed) 
        {   
        back.y += yScrollSpeed;

        } 
        else if (downPressed)
        {
            back.y -= yScrollSpeed;
        }   
    }



    function keyDownHandler(e:KeyboardEvent):void{
        if (e.keyCode == 37)
        {
        trace("left pressed");
        leftPressed = true;

        } 
        else if (e.keyCode == 39 )
        {
        trace("right pressed");
        rightPressed = true;

        } else if(e.keyCode == 38){
        trace("up pressed");
        upPressed = true;

        } else if(e.keyCode == 40){
        trace("down pressed");
        downPressed = true;
        }
        }

    function keyUpHandler(e:KeyboardEvent):void{
        if(e.keyCode == 37){
        trace("left released");
        upPressed = false;

        } else if(e.keyCode == 39){
        trace("right released");
        rightPressed = false;

        } else if(e.keyCode == 38){
        trace("up released");
        upPressed = false;

        } else if(e.keyCode ==40){
        trace("down released");
        downPressed = false;
        }
        }


   }

 }