CODE:
package index.base.game{

import flash.events.EventDispatcher;
import flash.events.KeyboardEvent;
import flash.events.Event;
import flash.display.InteractiveObject;

import index.base.events.DirectionEvent;

public class Direction extends EventDispatcher{

//方向表示
public static const UP:uint = 0;
public static const DOWN:uint = 1;
public static const LEFT:uint = 2;
public static const RIGHT:uint = 3;

//作用区域
public var area:InteractiveObject;
//是否单向
public var sole:Boolean;

//上下左右键值
private const directionAr:Array = new Array(4);

//是否上下左右
private var _up:Boolean = false;
private var _down:Boolean = false;
private var _left:Boolean = false;
private var _right:Boolean = false;

public function Direction(_area:InteractiveObject,isSole:Boolean = false,_up:uint = 38,_down:uint = 40,_left:uint = 37,_right:uint = 39){
area = _area;
sole = isSole;
directionAr[UP] = _up;
directionAr[DOWN] = _down;
directionAr[LEFT] = _left;
directionAr[RIGHT] = _right;
start();
}

//开始获取事件
public function start():void{
area.addEventListener(KeyboardEvent.KEY_DOWN,onKeyDown);
area.addEventListener(KeyboardEvent.KEY_UP,onKeyUp);
area.addEventListener(Event.ENTER_FRAME,onEnterFrame);
}

//事件帧频繁触发
private function onEnterFrame(e:Event):void{
var num:uint = Number(_up) Number(_down) Number(_left) Number(_right);
if(num == 0){
return;
}

var eve:DirectionEvent = new DirectionEvent(DirectionEvent.DO);
eve.up = _up;
eve.down = _down;
eve.left = _left;
eve.right = _right;
dispatchEvent(eve);
}

//停止获取事件
public function stop():void{
area.removeEventListener(KeyboardEvent.KEY_DOWN,onKeyDown);
area.removeEventListener(KeyboardEvent.KEY_UP,onKeyUp);
area.removeEventListener(Event.ENTER_FRAME,onEnterFrame);
}

//鼠标按下去事件
private function onKeyDown(e:KeyboardEvent):void{
key(e.keyCode,true)
}

//鼠标弹上来事件
private function onKeyUp(e:KeyboardEvent):void{
key(e.keyCode,false)
}

//变化状态
private function key(num:uint,isDown:Boolean):void{
switch(num){
case directionAr[UP]:
if(sole) clear();
_up = isDown;
break;
case directionAr[DOWN]:
if(sole) clear();
_down = isDown;
break;
case directionAr[LEFT]:
if(sole) clear();
_left = isDown;
break;
case directionAr[RIGHT]:
if(sole) clear();
_right = isDown;
break;
}
}

//设置按钮
public function setKey(num:uint,vars:uint):void{
directionAr[num] = vars;
}

//清空按键
public function clear():void{
_up = _down = _left = _right = false;
}
}
}Dot类源代码：

CODE:
package index.base.geom{

import flash.events.EventDispatcher;
import flash.display.DisplayObject;

import index.base.events.DotEvent;

public class Dot extends EventDispatcher{

private var _x:Number;
private var _y:Number;
private var _r:Number;
private var dis:DisplayObject;

public var isListen:Boolean;

public function Dot(x_:Number = 0,y_:Number = 0,r_:Number = 0,_isListen:Boolean = false){
_x = x_;
_y = y_;
_r = r_;
isListen = _isListen;
}

//绑定DisplayObject
public function bind(_dis:DisplayObject,isInTime:Boolean = false):void{
dis = _dis;
updata();
if(isInTime) dis.addEventListener("enterFrame",enterFrameFun);
}

//帧频繁事件
private function enterFrameFun(e:Object):void{
if(_x != dis.x) x = dis.x;
if(_y != dis.y) y = dis.y;
if(_r != dis.rotation) r = dis.rotation;
}

//更新xy数据
public function updata():void{
if(dis != null){
_x = dis.x;
_y = dis.y;
_r = dis.rotation;
}
}

//计算该点向R方向前进某距离后的点
public function go(num:Number,isChange:Boolean = false):Dot{
updata();
var yx:Number = Math.tan(_r * Math.PI / 180);
var tmpx:Number = num / Math.sqrt(Math.pow(yx,2) 1);
var tmpy:Number = tmpx * yx;
var n:int = Number(Math.abs(_r) <= 90) * 2 - 1;
var dot:Dot = new Dot(_x tmpx * n,_y tmpy * n,_r);
if(isChange){
x = dot.x;
y = dot.y;
}
return dot;
}

//计算该点与另外一点的距离
public function from(_dot:Dot,isQuadrant:Boolean = false):Number{
updata();
var num:Number = Math.sqrt(Math.pow(_dot.x - _x,2) Math.pow(_dot.y - _y,2));
if(!isQuadrant) num = Math.abs(num);
return num;
}

//计算该点与另外一点所形成的线段与水平线的夹角,按顺时间计算
public function angle(_dot:Dot,isRadian:Boolean = false):Number{
updata();
var numx:Number = _dot.x - _x;
var numy:Number = _dot.y - _y;
var num:Number = Math.atan(numy/numx);
if(!isRadian) num = num * 180 / Math.PI;
return num;
}

//返回当前点处在另外一点的哪个象限中 或 返回另外一点处在当前点的哪个象限中
public function quadrant(_dot:Dot,isMaster:Boolean = true):int{
updata();
if(_x == _dot.x || _y == _dot.y){
return 0;
}

var num:int;
var p1:Boolean = (_x - _dot.x) > 0;
var p2:Boolean = (_y - _dot.y) > 0;
num = isMaster ? (p1 ? (p2 ? 2 : 3) : (p2 ? 1 : 4)) : (p1 ? (p2 ? 4 : 1) : (p2 ? 3 : 2));

return num;
}

//返回该点距0点的距离
public function get length():Number{
updata();
var num:Number = Math.sqrt(Math.pow(_x,2) Math.pow(_y,2));
return num;
}

//清除显示对象
public function clear():void{
dis = null;
}

//改变旋转值
public function set r(num:Number):void{
_r = num;
if(dis != null) dis.rotation = num;
if(isListen) dispatchEvent(new DotEvent(DotEvent.R_CHANGE,true));
}

//改变旋转值
public function get r():Number{
updata();
return _r;
}

//改变X坐标
public function set x(num:Number):void{
_x = num;
if(dis != null) dis.x = num;
if(isListen) dispatchEvent(new DotEvent(DotEvent.X_CHANGE,true));
}

//设置X坐标
public function get x():Number{
updata();
return _x;
}

//改变Y坐标
public function set y(num:Number):void{
_y = num;
if(dis != null) dis.y = num;
if(isListen) dispatchEvent(new DotEvent(DotEvent.Y_CHANGE,true));
}

//设置Y坐标
public function get y():Number{
updata();
return _y;
}
}
}

DirectionEvent类源代码：

CODE:
package index.base.events{

import flash.events.Event;

public class DirectionEvent extends Event{

public var up:Boolean;
public var down:Boolean;
public var left:Boolean;
public var right:Boolean;

public static const DO:String = "do";

public function DirectionEvent(type:String){
super(type);
}
}
}DotEvent类源代码：

CODE:
package index.base.events{

import flash.events.Event;

public class DotEvent extends Event{

public static const X_CHANGE:String = "xChange";
public static const Y_CHANGE:String = "yChange";
public static const R_CHANGE:String = "rChange";

public function DotEvent(type:String, bubbles:Boolean = false, cancelable:Boolean = false){
super(type,bubbles,cancelable);
}
}
}

Flash AS3教程：Direction类和Dot类