You can keep track of whether each key is down or not by listening for all KEY_DOWN and KEY_UP events, and storing each key state in an array. I wrote a class a while ago to do just that (included at the end of my answer).
Then you are no longer tied to the event model to know if a certain key is down or not; you can periodically check every frame (or every timer interval). So you could have a function like:
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;
}
which would take into account all possible combinations of arrow key presses. If you want the net displacement to be constant (e.g. when going right and down at same time, the object moves X pixels diagonally, as opposed to X pixels in both horizontal and vertical directions), the code becomes:
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;
}
Here is the Input class I wrote (don't forget to call init from the document class). Note that it also keeps track of mouse stuff; you can delete that if you don't need it:
/*******************************************************************************
* 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;
}
}
}