您可以通过侦听所有 KEY_DOWN 和 KEY_UP 事件并将每个键状态存储在数组中来跟踪每个键是否已关闭。我不久前写了一个课程来做到这一点（包括在我的答案的末尾）。
然后你就不再依赖于事件模型来知道某个键是否被按下；您可以定期检查每一帧（或每个计时器间隔）。所以你可以有这样的功能：
function enterFrameCallback(e:Event):void
{
var speed:Number = 1.0; // net pixels per frame movement
thing.x += (
-(int)Input.isKeyDown(Keyboard.LEFT)
+(int)Input.isKeyDown(Keyboard.RIGHT)
) * speed;
thing.y += (
-(int)Input.isKeyDown(Keyboard.UP)
+(int)Input.isKeyDown(Keyboard.DOWN)
) * speed;
}
这将考虑到所有可能的箭头按键组合。如果您希望净位移是恒定的（例如，当同时向右和向下移动时，对象沿对角线移动 X 像素，而不是在水平和垂直方向上移动 X 像素），代码变为：
function enterFrameCallback(e:Event):void
{
var speed:Number = 1.0; // net pixels per frame movement
var displacement:Point = new Point();
displacement.x = (
-(int)Input.isKeyDown(Keyboard.LEFT)
+(int)Input.isKeyDown(Keyboard.RIGHT)
);
displacement.y = (
-(int)Input.isKeyDown(Keyboard.UP)
+(int)Input.isKeyDown(Keyboard.DOWN)
);
displacement.normalize(speed);
thing.x += displacement.x;
thing.y += displacement.y;
}
这是我编写的 Input 类（不要忘记从文档类中调用 init）。请注意，它还跟踪鼠标内容；如果你不需要它，你可以删除它：
/*******************************************************************************
* DESCRIPTION: Defines a simple input class that allows the programmer to
* determine at any instant whether a specific key is down or not,
* or if the mouse button is down or not (and where the cursor
* is respective to a certain DisplayObject).
* USAGE: Call init once before using any other methods, and pass a reference to
* the stage. Use the public methods commented below to query input states.
*******************************************************************************/
package
{
import flash.events.KeyboardEvent;
import flash.events.MouseEvent;
import flash.display.Stage;
import flash.geom.Point;
import flash.display.DisplayObject;
public class Input
{
private static var keyState:Array = new Array();
private static var _mouseDown:Boolean = false;
private static var mouseLoc:Point = new Point();
private static var mouseDownLoc:Point = new Point();
// Call before any other functions in this class:
public static function init(stage:Stage):void
{
stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyDown, false, 10);
stage.addEventListener(KeyboardEvent.KEY_UP, onKeyUp, false, 10);
stage.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown, false, 10);
stage.addEventListener(MouseEvent.MOUSE_UP, onMouseUp, false, 10);
stage.addEventListener(MouseEvent.MOUSE_MOVE, onMouseMove, false, 10);
}
// Call to query whether a certain keyboard key is down.
// For a non-printable key: Input.isKeyDown(Keyboard.KEY)
// For a letter (case insensitive): Input.isKeyDown('A')
public static function isKeyDown(key:*):Boolean
{
if (typeof key == "string") {
key = key.toUpperCase().charCodeAt(0);
}
return keyState[key];
}
// Property that is true if the mouse is down, false otherwise:
public static function get mouseDown():Boolean
{
return _mouseDown;
}
// Gets the current coordinates of the mouse with respect to a certain DisplayObject.
// Leaving out the DisplayObject paramter will return the mouse location with respect
// to the stage (global coordinates):
public static function getMouseLoc(respectiveTo:DisplayObject = null):Point
{
if (respectiveTo == null) {
return mouseLoc.clone();
}
return respectiveTo.globalToLocal(mouseLoc);
}
// Gets the coordinates where the mouse was when it was last down or up, with respect
// to a certain DisplayObject. Leaving out the DisplayObject paramter will return the
// location with respect to the stage (global coordinates):
public static function getMouseDownLoc(respectiveTo:DisplayObject = null):Point
{
if (respectiveTo == null) {
return mouseDownLoc.clone();
}
return respectiveTo.globalToLocal(mouseDownLoc);
}
// Resets the state of the keyboard and mouse:
public static function reset():void
{
for (var i:String in keyState) {
keyState[i] = false;
}
_mouseDown = false;
mouseLoc = new Point();
mouseDownLoc = new Point();
}
///// PRIVATE METHODS BEWLOW /////
private static function onMouseDown(e:MouseEvent):void
{
_mouseDown = true;
mouseDownLoc = new Point(e.stageX, e.stageY);
}
private static function onMouseUp(e:MouseEvent):void
{
_mouseDown = false;
mouseDownLoc = new Point(e.stageX, e.stageY);
}
private static function onMouseMove(e:MouseEvent):void
{
mouseLoc = new Point(e.stageX, e.stageY);
}
private static function onKeyDown(e:KeyboardEvent):void
{
keyState[e.keyCode] = true;
}
private static function onKeyUp(e:KeyboardEvent):void
{
keyState[e.keyCode] = false;
}
}
}