Java游戏服务器开发之A星算法
学习这个主要是用于寻路算法。
代码也是大部分参考里面，原本是C#的，用Java实现了一遍。
一般看视频的话，基本一知半解，自己敲一遍，基本就能了解了
我先直接放代码，先跑成功后，再说明下整个实现
首先，需要将我们的地图虚拟化，我们用Point表示。
其次，创建整个地图，按照长宽来初始化。initMap
接着，写出计算FGH的值(先不用管是什么)的函数。calcF
再者，就是书写查找路径的方法。 findPath
1.循环"开启列表"，while (openList.size() > 0)
2.找到列表中F值最小的点M。findMinFOfPoint
3.找到M点周边可以到达的点数组L。getSurroundPoints
4.使用相关条件过滤掉一部分L中的点。pointsFilter
5.循环L，判断里面的G值是否比原来的更小(更优)for (Point surroundPoint : surroundPoints)
最后，就是输出结果showLoad
看具体的代码
Point类
package com.lizhao.astar.siki;
public class Point implements Comparable<Point> {
private Point parent;
private int x;
private int y;
private float F;
private float G;
private float H;
private boolean isWall = false;
private boolean isLoad = false;
public Point(int x, int y) {
this(x, y, null);
}
public Point(int x, int y, Point parent) {
this.x = x;
this.y = y;
this.parent = parent;
}
public void UpdateParent(Point parent, float g) {
this.parent = parent;
this.G = g;
F = G + H;
}
public void updateFGH(float f, float g, float h) {
this.F = f;
this.G = g;
this.H = h;
}
public Point getParent() {
return parent;
}
public void setParent(Point parent) {
this.parent = parent;
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
public float getF() {
return F;
}
public void setF(float f) {
F = f;
}
public float getG() {
return G;
}
public void setG(float g) {
G = g;
}
public float getH() {
return H;
}
public void setH(float h) {
H = h;
}
public boolean isWall() {
return isWall;
}
public void setWall(boolean wall) {
isWall = wall;
}
public boolean isLoad() {
return isLoad;
}
public void setLoad(boolean load) {
isLoad = load;
}
@Override
public int compareTo(Point point) {
return Float.compare(F, point.getF());
}
@Override
public String toString() {
return "Point " + (getX() + 1) + "," + (getY() + 1);
}
}
initMap方法
public void initMap() {
for (int x = 0; x < mapWith; x++) {
for (int y = 0; y < mapHeight; y++) {
map[x][y] = new Point(x, y);
}
}
// map[6][3].setWall(true);
map[6][4].setWall(true);
map[6][5].setWall(true);
map[6][6].setWall(true);
// map[4][5].setWall(true);
// map[4][6].setWall(true);
}calcF方法
/*************************************************************
*第一步，写出计算FGH的值
**********************************************************/
/**
* 计算F值
*
* @param now 当前点
* @param end 终点
*/
private void calcF(Point now, Point end) {
//F = G + H
// H 表示从指定的方格移动到终点 B 的预计耗费 (H 有很多计算方法, 这里我们设定只可以
//上下左右移动).
//G 表示从起点 A 移动到网格上指定方格的移动耗费 (可沿斜方向移动).
float h = calcH(now, end);
float g = calcG(now, now.getParent());
float f = g + h;
now.updateFGH(f, g, h);
}
/**
* 获取H值
* H 表示从指定的方格移动到终点 B 的预计耗费
* (H 有很多计算方法, 这里我们设定只可以上下左右移动).
*
* @param start
* @param end
* @return
*/
private float calcH(@NotNull Point start, @NotNull Point end) {
return Math.abs(end.getX() - start.getX()) + Math.abs(end.getY() - start.getY());
}
/**
* 获取G值
* G 表示从起点 A 移动到网格上指定方格的移动耗费 (可沿斜方向移动).
* 父节点到走到该节点的消耗
*
* @param start
* @param parent
* @return
*/
private float calcG(@NotNull Point start, @NotNull Point parent) {
float g = 0;
if (start.getParent() == null) {
g = 0;
} else {
g = PointUtil.getDistance(start, parent) + parent.getG();
}
return g;
}
findPath方法
findMinFOfPoint 方法
/**
* 开启列表中F值最小的点
*
* @param openList
* @return
*/
private Point findMinFOfPoint(List<Point> openList) {
float f = Float.MAX_VALUE;
Point temp = null;
for (Point p : openList) {
if (p.getF() < f) {
temp = p;
f = p.getF();
}
}
return temp;
}
getSurroundPoints 方法、
/**
* 周围的点
*
* @param point
* @return
*/
private List<Point> getSurroundPoints(Point point) {
Point up = null, down = null, left = null, right = null;
Point lu = null, ru = null, ld = null, rd = null;
if (point.getY() < mapHeight - 1) {
up = map[point.getX()][point.getY() + 1];
}
if (point.getY() > 0) {
down = map[point.getX()][point.getY() - 1];
}
if (point.getX() > 0) {
left = map[point.getX() - 1][point.getY()];
}
if (point.getX() < mapWith - 1) {
right = map[point.getX() + 1][point.getY()];
}
if (up != null && left != null) {
lu = map[point.getX() - 1][point.getY() + 1];
}
if (up != null && right != null) {
ru = map[point.getX() + 1][point.getY() + 1];
}
if (down != null && left != null) {
ld = map[point.getX() - 1][point.getY() - 1];
}
if (down != null && right != null) {
rd = map[point.getX() + 1][point.getY() - 1];
}
List<Point> list = new ArrayList<Point>();
if (down != null && down.isWall() == false) {
list.add(down);
}
if (up != null && up.isWall() == false) {
list.add(up);
}
if (left != null && left.isWall() == false) {
list.add(left);
}
if (right != null && right.isWall() == false) {
list.add(right);
}
if (lu != null && lu.isWall() == false && left.isWall() == false && up.isWall() == false) {
list.add(lu);
}
if (ld != null && ld.isWall() == false && left.isWall() == false && down.isWall() == false) {
list.add(ld);
}
if (ru != null && ru.isWall() == false && right.isWall() == false && up.isWall() == false) {
list.add(ru);
}
if (rd != null && rd.isWall() == false && right.isWall() == false && down.isWall() == false) {
list.add(rd);
}
return list;
}
pointsFilter 方法
/**
* 过滤掉周围的点
*
* @param src
* @param closeList
*/
private void pointsFilter(List<Point> src, List<Point> closeList) {
for (Point p : closeList) {
if (src.indexOf(p) > -1) {
src.remove(p);
}
}
}
findPath具体
private void findPath(Point start, Point end) {
List<Point> openList = new ArrayList<Point>();
List<Point> closeList = new ArrayList<Point>();
openList.add(start);
while (openList.size() > 0) {
Point point = findMinFOfPoint(openList);
openList.remove(point);
closeList.add(point);
List<Point> surroundPoints = getSurroundPoints(point);
pointsFilter(surroundPoints, closeList);
for (Point surroundPoint : surroundPoints) {
if (openList.indexOf(surroundPoint) > -1) {
float nowG = calcG(surroundPoint, point);
if (nowG < surroundPoint.getG()) {
surroundPoint.UpdateParent(point, nowG);
}
} else {
surroundPoint.setParent(point);
calcF(surroundPoint, end);
openList.add(surroundPoint);
}
}
//判断一下
if (openList.indexOf(end) > -1) {
break;
}
}
}
showLoad方法
private void showLoad() {
for (int i = 0; i < map.length; i++) {
for (int j = 0; j < map[i].length; j++) {
if (map[i][j].isLoad()) {
System.out.print("$");
} else if (map[i][j].isWall()) {
System.out.print(1);
} else if (map[i][j].getParent() != null) {
System.out.print(3);
} else {
System.out.print(0);
}
System.out.print(",");
}
System.out.println();
}
}写个测试方法：
//测试A星算法
public static void testAStar() {
AStar aStar = new AStar();
aStar.initMap();
Point start = aStar.map[4][4];
Point end = aStar.map[8][5];
aStar.findPath(start, end);
aStar.showPath(start, end);
aStar.showLoad();
System.out.println("Hello World! ");
}
最后的输出结果，0是地图，1是墙，3是被探索过的区域，$是具体的路径
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,
0,0,3,3,3,3,1,0,0,0,0,0,0,0,0,
6 0,0,3,3,3,3,1,3,$,3,0,0,0,0,0,
5 0,0,3,3,$,3,1,3,$,3,0,0,0,0,0,
4 0,0,0,3,3,$,$,$,3,3,0,0,0,0,0,
0,0,0,0,3,3,3,3,3,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
5,6
6,4 14+50
6,5 10+40
6,6 14+30
6,7 24+40
nice
上面的代码在码云上 https://gitee.com/lizhaoandroid/BehaviorTree，在com.lizhao.astar.siki包下面
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