A*尋路算法代碼實現

A*尋路的原理，網上很多，可以看這里

var A_STAR_DISTANCE = 7; //像素大小，越小越精確，同時越耗時
var A_STAR_G_EXPEND_MIN = 10; //上下左右G值消耗數
var A_STAR_G_EXPEND_MAX = 14; //斜角G值消耗數

var HelloWorldLayer = cc.Layer.extend({
sprite:null, //角色
aStarPathArray:[], //最終角色要行走的路徑
aStarBarrierArray:[], //地圖障礙物
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); //繪制障礙物
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(); //在屏幕上顯示障礙物
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*算法開始
cc.log("算法耗時:"+(new Date().getTime() - t)+"ms"); //計算起點到終點的算法耗時
}
}
}, this);


return true;
},
getStartAndEndPoint:function (event) { //得到起始點和終點坐標
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; //判斷終點是否在障礙物上，是的話就提示路徑走不了
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("你要去的位置有障礙物，請換條路線");
break;
}
}
if(!endPointIsObstacle)
this.findingPath(sp,ep);
},
findingPath:function(startPoint,endPoint){ //A*算法
var openList = []; //初始化開啟列表
var closeList = []; //初始化關閉列表
startPoint.ag = 0;
startPoint.ah = 0;
startPoint.af = startPoint.ag + startPoint.ah; //起點的G,H,F值為0
openList.push(startPoint); //起點加入開啟列表
var findTheWay = false;
do{
var centerNode = this.findMinNode(openList); //尋找F值最低的節點
openList.remove(centerNode); //將此節點從開啟列表中刪除，為了下次遍歷開啟列表的時候不再出現此節點
closeList.push(centerNode); //並將此節點加入到關閉列表
for(var i=0;i<8;i++) //遍歷此節點周圍的節點，並給這些節點加入坐標屬性和G值
{
var aroundNode = {};
switch (i){
case 0:
aroundNode.coordX = centerNode.coordX+A_STAR_DISTANCE; //坐標屬性
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)); //判斷當前節點是否在障礙物形成的方框里
if(aroundNode.isOb)
break;
}
if (aroundNode.isOb){ //如果是障礙物，跳過

}
else if(closeList.hasObject(aroundNode)){ //如果在關閉列表里，跳過

}
else if(!openList.hasObject(aroundNode)){ //如果不在開啟列表里，加入到開啟列表
aroundNode.parentPath = centerNode;
if (Math.abs(aroundNode.coordX-endPoint.coordX)<=A_STAR_DISTANCE/2 && Math.abs(aroundNode.coordY-endPoint.coordY)<=A_STAR_DISTANCE/2) //如果節點和終點的值相近，那么A*算法結束，得到路徑
{
findTheWay = true;
var pathArry = [];
this.gettingAStarPath(aroundNode,pathArry); //尋找路徑
pathArry.splice(0,0,{starX:endPoint.coordX,starY:endPoint.coordY}); //加終點到數組頭部
pathArry.splice(pathArry.length-1,1); //刪一項數組底部的起點數據，此時的數組是最終的路徑數組

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

this.unschedule(this.thePathSelector);
this.schedule(this.thePathSelector,null,pathArry.length-1);
break; //找到最短路徑並跳出循環
}
if (aroundNode.coordX!=centerNode.coordX && aroundNode.coordY!=centerNode.coordY) //確定中心節點和周圍節點形成的角度，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)){ //如果在開啟列表里
var newExpend = A_STAR_G_EXPEND_MIN*A_STAR_DISTANCE;
if (aroundNode.coordX!=centerNode.coordX && aroundNode.coordY!=centerNode.coordY) //確定中心節點和周圍節點形成的角度，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值小於周圍節點本身的g值，那么周圍節點的父節點改為當前中心節點，並重新計算其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);
}
});

//這里給Array數組添加3個實例方法
Array.prototype.aStarIndexOf = function(val) { //通過對象尋找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) { //刪除相應的對象
var index = this.aStarIndexOf(val);
if (index > -1) {
this.splice(index, 1);
}
};

Array.prototype.hasObject = function(val){ //判斷是否是同一個對象
for (var i = 0; i < this.length; i++){
if (this[i].coordX==val.coordX && this[i].coordY==val.coordY)
return true;
}
return false;
};