1. 简介
a星寻路作为启发式搜索，在游戏开发中经常使用，性能比dps要好，也比较简单好实现，通用原理网上很多这里就不多做详解了，还不熟悉的可以参考：简书链接;
2. 实现
伪码如下
把当前点加入openList
while(openList不为空){
取出f值最小的点作为当前点curGrid
if(curGrid == endGrid) 查找结束，生成路径
查找curGrid周围的点，如果不在openList则加入openList并重新排序, 这里要注意如果8方向查找要注意相邻的是不是障碍物
把curGrid从openList移除并加入closeList
if (openList为空) 则查找失败，没有路径
}
代码实现
let Grid = cc.Class({
ctor(){
this.x = 0;
this.y = 0;
this.f = 0;
this.g = 0;
this.h = 0;
this.parent = null;
this.type = 0; // -1障碍物， 0正常， 1目标点， 2起点
}
});
let AStar = cc.Class({
extends: cc.Component,
properties:{
map: cc.Graphics,
},
onLoad(){
this._gridW = 50; // 单元格子宽度
this._gridH = 50; // 单元格子高度
this.mapH = 13; // 纵向格子数量
this.mapW = 24; // 横向格子数量
this.is8dir = true; // 是否8方向寻路
this.node.on(cc.Node.EventType.TOUCH_MOVE, this.onTouchMove, this);
this.node.on(cc.Node.EventType.TOUCH_END, this.onTouchEnd, this);
this.initMap();
},
onTouchMove(event){
let pos = event.getLocation();
let x = Math.floor(pos.x / (this._gridW + 2));
let y = Math.floor(pos.y / (this._gridH + 2));
if (this.gridsList[x][y].type == 0){
this.gridsList[x][y].type = -1;
this.draw(x, y, cc.Color.RED);
}
cc.log(x + "," + y);
},
onTouchEnd(){
// 开始寻路
this.findPath(cc.v2(3, 8), cc.v2(19, 5));
},
initMap(){
this.openList = [];
this.closeList = [];
this.path = [];
// 初始化格子二维数组
this.gridsList = new Array(this.mapW + 1);
for (let col=0;col<this.gridsList.length; col++){
this.gridsList[col] = new Array(this.mapH + 1);
}
this.map.clear();
for (let col=0; col<= this.mapW; col++){
for (let row=0; row<=this.mapH; row++){
this.draw(col, row);
this.addGrid(col, row, 0);
}
}
// 设置起点和终点
let startX = 3;
let startY = 8;
let endX = 19;
let endY = 5;
this.gridsList[startX][startY].type = 1;
this.draw(startX, startY, cc.Color.YELLOW);
this.gridsList[endX][endY].type = 2;
this.draw(endX, endY, cc.Color.BLUE);
},
addGrid(x, y, type){
let grid = new Grid();
grid.x = x;
grid.y = y;
grid.type = type;
this.gridsList[x][y] = grid;
},
_sortFunc(x, y){
return x.f - y.f;
},
generatePath(grid){
this.path.push(grid);
while (grid.parent){
grid = grid.parent;
this.path.push(grid);
}
cc.log("path.length: " + this.path.length);
for (let i=0; i<this.path.length; i++){
// 起点终点不覆盖，方便看效果
if (i!=0 && i!= this.path.length-1){
let grid = this.path[i];
this.draw(grid.x, grid.y, cc.Color.GREEN);
}
}
},
findPath(startPos, endPos){
let startGrid = this.gridsList[startPos.x][startPos.y];
let endGrid = this.gridsList[endPos.x][endPos.y];
this.openList.push(startGrid);
let curGrid = this.openList[0];
while (this.openList.length > 0 && curGrid.type != 2){
// 每次都取出f值最小的节点进行查找
curGrid = this.openList[0];
if (curGrid.type == 2){
cc.log("find path success.");
this.generatePath(curGrid);
return;
}
for(let i=-1; i<=1; i++){
for(let j=-1; j<=1; j++){
if (i !=0 || j != 0){
let col = curGrid.x + i;
let row = curGrid.y + j;
if (col >= 0 && row >= 0 && col <= this.mapW && row <= this.mapH
&& this.gridsList[col][row].type != -1
&& this.closeList.indexOf(this.gridsList[col][row]) < 0){
if (this.is8dir){
// 8方向 斜向走动时要考虑相邻的是不是障碍物
if (this.gridsList[col-i][row].type == -1 || this.gridsList[col][row-j].type == -1){
continue;
}
} else {
// 四方形行走
if (Math.abs(i) == Math.abs(j)){
continue;
}
}
// 计算g值
let g = curGrid.g + parseInt(Math.sqrt(Math.pow(i*10,2) + Math.pow(j*10,2)));
if (this.gridsList[col][row].g == 0 || this.gridsList[col][row].g > g){
this.gridsList[col][row].g = g;
// 更新父节点
this.gridsList[col][row].parent = curGrid;
}
// 计算h值 manhattan估算法
this.gridsList[col][row].h = Math.abs(endPos.x - col) + Math.abs(endPos.y - row);
// 更新f值
this.gridsList[col][row].f = this.gridsList[col][row].g + this.gridsList[col][row].h;
// 如果不在开放列表里则添加到开放列表里
if (this.openList.indexOf(this.gridsList[col][row]) < 0){
this.openList.push(this.gridsList[col][row]);
}
// 重新按照f值排序（升序排列)
this.openList.sort(this._sortFunc);
}
}
}
}
// 遍历完四周节点后把当前节点加入关闭列表
this.closeList.push(curGrid);
// 从开发列表把当前节点移除
this.openList.splice(this.openList.indexOf(curGrid), 1);
if (this.openList.length <= 0){
cc.log("find path failed.");
}
}
},
draw(col, row, color){
color = color != undefined ? color : cc.Color.GRAY;
this.map.fillColor = color;
let posX = 2 + col * (this._gridW + 2);
let posY = 2 + row * (this._gridH + 2);
this.map.fillRect(posX,posY,this._gridW,this._gridH);
}
});
3. 效果图及链接
