A*寻路算法 (cocos2d-js详细代码)

看了几天的A*算法，感觉要成为一个游戏开发者，有必要把这个著名的算法拿到手。

网上有此算法的代码片段，但主要还是些模板类的伪代码，所以想分享一段完整的A*算法代码供大家更好的理解！（这里使用的是js语言和cocos2d游戏引擎）

对于A*算法概念性的描述，请看这里，本篇主要以代码为主。

下面是我的学习成果，有晦涩和需改进的地方欢迎吐槽！

var A_STAR_DISTANCE = 7;                    //像素大小，越小越精确，同时越耗时
var A_STAR_G_EXPEND_MIN = 10;               //上下左右G值消耗数
var A_STAR_G_EXPEND_MAX = 14;               //斜角G值消耗数

var HelloWorldLayer = cc.Layer.extend({
    sprite:null,                            //角色
    aStarPathArray:[],                      //最终角色要行走的路径
    aStarBarrierArray:[],                   //地图障碍物
    testNumber:1,
    ctor:function () {
        //////////////////////////////
        // 1. super init first
        this._super();
        /////////////////////////////
        // 2. add a menu item with "X" image, which is clicked to quit the program
        //    you may modify it.
        // ask director the window size
        var size = cc.director.getWinSize();

        this.sprite = cc.Sprite.create(res.Plane_png);   //角色初始化
        this.sprite.attr({
            x: 150,
            y: 50,
            rotation: 90
        });
        this.addChild(this.sprite, 0);

        var barrier1 = cc.rect(200,50,50,350);       //绘制障碍物
        var barrier2 = cc.rect(250,50,350,50);
        var barrier3 = cc.rect(250,350,350,50);
        this.aStarBarrierArray.push(barrier1);
        this.aStarBarrierArray.push(barrier2);
        this.aStarBarrierArray.push(barrier3);

        var drawBarrier = cc.DrawNode.create();             //在屏幕上显示障碍物
        this.addChild(drawBarrier, 10);
        var vertices = [cc.p(200,50),cc.p(600,50),cc.p(600,100),cc.p(250,100),cc.p(250,350),cc.p(600,350),cc.p(600,400),cc.p(200,400)];
        drawBarrier.drawPoly(vertices,null,2,cc.color(255,0,0,255));

        if ('mouse' in cc.sys.capabilities)
            cc.eventManager.addListener({
                event: cc.EventListener.MOUSE,
                onMouseUp:function(event){
                    if(event.getButton() != undefined)
                    {
                        var t = new Date().getTime();
                        event.getCurrentTarget().getStartAndEndPoint(event);      //A*算法开始
                        cc.log("算法耗时:"+(new Date().getTime() - t)+"ms");          //计算起点到终点的算法耗时
                    }
                }
            }, this);


        return true;
    },
    getStartAndEndPoint:function (event) {                                         //得到起始点和终点坐标
        var sp = {coordX:parseInt(this.sprite.x,10),coordY:parseInt(this.sprite.y,10)};
        var ep = {coordX:parseInt(event.getLocation().x,10),coordY:parseInt(event.getLocation().y,10)};
        var endPointIsObstacle = false;                                            //判断终点是否在障碍物上，是的话就提示路径走不了
        for (var theBarrierIndex=0; theBarrierIndex<this.aStarBarrierArray.length; theBarrierIndex++){
            if(cc.rectContainsPoint(this.aStarBarrierArray[theBarrierIndex],cc.p(ep.coordX,ep.coordY)))
            {
                endPointIsObstacle = true;
                cc.log("你要去的位置有障碍物，请换条路线");
                break;
            }
        }
        if(!endPointIsObstacle)
            this.findingPath(sp,ep);
    },
    findingPath:function(startPoint,endPoint){     //A*算法
        var openList  = [];                      //初始化开启列表
        var closeList = [];                      //初始化关闭列表
        startPoint.ag = 0;
        startPoint.ah = 0;
        startPoint.af = startPoint.ag + startPoint.ah;   //起点的G,H,F值为0
        openList.push(startPoint);               //起点加入开启列表
        var findTheWay = false;
        do{
            var centerNode = this.findMinNode(openList);  //寻找F值最低的节点
            openList.remove(centerNode);         //将此节点从开启列表中删除，为了下次遍历开启列表的时候不再出现此节点
            closeList.push(centerNode);          //并将此节点加入到关闭列表
            for(var i=0;i<8;i++)                 //遍历此节点周围的节点，并给这些节点加入坐标属性和G值
            {
                var aroundNode = {};
                switch (i){
                    case 0:
                        aroundNode.coordX = centerNode.coordX+A_STAR_DISTANCE;                //坐标属性
                        aroundNode.coordY = centerNode.coordY+A_STAR_DISTANCE;
                        break;
                    case 1:
                        aroundNode.coordX = centerNode.coordX+A_STAR_DISTANCE;
                        aroundNode.coordY = centerNode.coordY;
                        break;
                    case 2:
                        aroundNode.coordX = centerNode.coordX+A_STAR_DISTANCE;
                        aroundNode.coordY = centerNode.coordY-A_STAR_DISTANCE;
                        break;
                    case 3:
                        aroundNode.coordX = centerNode.coordX;
                        aroundNode.coordY = centerNode.coordY-A_STAR_DISTANCE;
                        break;
                    case 4:
                        aroundNode.coordX = centerNode.coordX-A_STAR_DISTANCE;
                        aroundNode.coordY = centerNode.coordY-A_STAR_DISTANCE;
                        break;
                    case 5:
                        aroundNode.coordX = centerNode.coordX-A_STAR_DISTANCE;
                        aroundNode.coordY = centerNode.coordY;
                        break;
                    case 6:
                        aroundNode.coordX = centerNode.coordX-A_STAR_DISTANCE;
                        aroundNode.coordY = centerNode.coordY+A_STAR_DISTANCE;
                        break;
                    case 7:
                        aroundNode.coordX = centerNode.coordX;
                        aroundNode.coordY = centerNode.coordY+A_STAR_DISTANCE;
                        break;
                }
                for (var barrierIndex=0; barrierIndex<this.aStarBarrierArray.length; barrierIndex++){
                    aroundNode.isOb = cc.rectContainsPoint(this.aStarBarrierArray[barrierIndex],cc.p(aroundNode.coordX,aroundNode.coordY));   //判断当前节点是否在障碍物形成的方框里
                    if(aroundNode.isOb)
                        break;
                }
                if (aroundNode.isOb){                                       //如果是障碍物，跳过

                }
                else if(closeList.hasObject(aroundNode)){                         //如果在关闭列表里，跳过

                }
                else if(!openList.hasObject(aroundNode)){                          //如果不在开启列表里，加入到开启列表
                    aroundNode.parentPath = centerNode;
                    if (Math.abs(aroundNode.coordX-endPoint.coordX)<=A_STAR_DISTANCE/2 && Math.abs(aroundNode.coordY-endPoint.coordY)<=A_STAR_DISTANCE/2)  //如果节点和终点的值相近，那么A*算法结束，得到路径
                    {
                        findTheWay = true;
                        var pathArry = [];
                        this.gettingAStarPath(aroundNode,pathArry);                           //寻找路径
                        pathArry.splice(0,0,{starX:endPoint.coordX,starY:endPoint.coordY});   //加终点到数组头部
                        pathArry.splice(pathArry.length-1,1);                                 //删一项数组底部的起点数据，此时的数组是最终的路径数组

                        this.aStarPathArray = [];
                        this.aStarPathArray = pathArry;
                        this.aStarPathArray.theIndex = this.aStarPathArray.length;

                        this.unschedule(this.thePathSelector);
                        this.schedule(this.thePathSelector,null,pathArry.length-1);
                        break;           //找到最短路径并跳出循环
                    }
                    if (aroundNode.coordX!=centerNode.coordX && aroundNode.coordY!=centerNode.coordY)   //确定中心节点和周围节点形成的角度，正交G值消耗10*像素，斜角G值消耗14*像素
                        aroundNode.ag = centerNode.ag + A_STAR_G_EXPEND_MAX*A_STAR_DISTANCE;
                    else
                        aroundNode.ag = centerNode.ag + A_STAR_G_EXPEND_MIN*A_STAR_DISTANCE;
                    aroundNode.af = this.getAF(aroundNode,endPoint);
                    openList.push(aroundNode);
                }
                else if(openList.hasObject(aroundNode)){                           //如果在开启列表里
                    var newExpend = A_STAR_G_EXPEND_MIN*A_STAR_DISTANCE;
                    if (aroundNode.coordX!=centerNode.coordX && aroundNode.coordY!=centerNode.coordY)   //确定中心节点和周围节点形成的角度，正交G值消耗10*像素，斜角G值消耗14*像素
                        newExpend = A_STAR_G_EXPEND_MAX*A_STAR_DISTANCE;
                    if (centerNode.ag + newExpend < aroundNode.ag){                //如果新的g值小于周围节点本身的g值，那么周围节点的父节点改为当前中心节点，并重新计算其F值
                        aroundNode.parentPath = centerNode;
                        aroundNode.ag = centerNode.ag + newExpend;
                        aroundNode.af = this.getAF(aroundNode,endPoint);
                    }
                }
            }
        }while(!findTheWay)

    },
    findMinNode:function(openListArray){
        var minNode = openListArray[0];
        for (var i=0;i<openListArray.length;i++)
        {
            if (minNode.af>openListArray[i].af) minNode=openListArray[i];
        }
        return minNode;
    },
    getAF:function(thisNode,endNode){
        var aHExpend = (Math.abs(thisNode.coordX-endNode.coordX) + Math.abs(thisNode.coordY-endNode.coordY))*A_STAR_G_EXPEND_MIN;
        return aHExpend+thisNode.ag;
    },
    gettingAStarPath:function(laseNode,array){
        if(laseNode.parentPath != null)
        {
            array.push({starX:laseNode.parentPath.coordX,starY:laseNode.parentPath.coordY});
            this.gettingAStarPath(laseNode.parentPath,array);
        }
    },
    thePathSelector:function(){
        this.roleRunThePath(this.aStarPathArray);
    },
    roleRunThePath:function(array){
        this.sprite.x = array[--array.theIndex].starX;
        this.sprite.y = array[array.theIndex].starY;
    }
});

var HelloWorldScene = cc.Scene.extend({
    onEnter:function () {
        this._super();
        var layer = new HelloWorldLayer();
        this.addChild(layer);
    }
});

//这里给Array数组添加3个实例方法
Array.prototype.aStarIndexOf = function(val) {        //通过对象寻找index值
    for (var i = 0; i < this.length; i++) {
        if (this[i].coordX==val.coordX && this[i].coordY==val.coordY) return i;
    }
    return -1;
};
Array.prototype.remove = function(val) {         //删除相应的对象
    var index = this.aStarIndexOf(val);
    if (index > -1) {
        this.splice(index, 1);
    }
};

Array.prototype.hasObject = function(val){       //判断是否是同一个对象
    for (var i = 0; i < this.length; i++){
        if (this[i].coordX==val.coordX && this[i].coordY==val.coordY)
            return true;
    }
    return false;
};

如下图，飞机在寻找路径的时候会避开红色区域。