Java A*相邻节点nullpointerexception
尝试做一些A*的事情，我经常在第129行得到一个NullPointerExceptionJava A*相邻节点nullpointerexception,java,arraylist,nullpointerexception,a-star,Java,Arraylist,Nullpointerexception,A Star,尝试做一些A*的事情，我经常在第129行得到一个NullPointerException public class GameMap { int tileW = 64; int tileH = 36; int tiles = 2304; ArrayList<Node> nodes = new ArrayList<Node>(); public GameMap(int width, int height) { int widthtest = 640; i
public class GameMap {
int tileW = 64;
int tileH = 36;
int tiles = 2304;
ArrayList<Node> nodes = new ArrayList<Node>();
public GameMap(int width, int height) {
int widthtest = 640;
int heighttest = 360;
for (int y = 0; y<tileH; y++){
for (int x = 0; x<tileW; x++){
nodes.add(new Node(x,y,false,null,10000));
//System.out.println("node added at x:" + x + " and y:" + y + " w/tilenum: " + nodes.size());
}
}
}
public void blockNode(int x, int y){
int tilenum = tileNum(x,y);
nodes.get(tilenum).blocked = true;
System.out.println("blocked node " + tilenum);
}
public int tileNum(int x, int y){
int tilenum = x+(y*64);
return tilenum;
}
public ArrayList<Node> findPath(int sx, int sy, int tx, int ty){
ArrayList<Node> open = new ArrayList<Node>();
ArrayList<Node> closed = new ArrayList<Node>();
ArrayList<Node> path = new ArrayList<Node>();
ArrayList<Node> adjList = new ArrayList<Node>();
Node startNode = new Node(sx, sy, false, null, getF(sx,sy,tx,ty));
Node endNode = new Node(tx, ty, false, null, 0);
Node currentNode = null;
open.add(startNode);
while(currentNode != endNode && open.size()>0 && endNode.parent == null){
currentNode = findBestNode(open);
adjList = getAdj(currentNode);
if(currentNode.equals(endNode)){
continue;
}
else{
open.remove(currentNode);
closed.add(currentNode);
for(int i = 0 ; i<adjList.size() ; i++){
if(adjList.get(i).blocked || closed.contains(adjList.get(i))){
continue;
}
if(!open.contains(adjList.get(i))){
open.add(adjList.get(i));
adjList.get(i).parent = currentNode;
}
else{
int newDistance = getF(currentNode.x, currentNode.y, tx, ty);
if(newDistance < currentNode.fscore){
adjList.get(i).parent = currentNode;
adjList.get(i).fscore = newDistance;
}
}
}
}
}
if(endNode.parent != null){
path = generatePath(startNode, endNode);
}
return path;
}
private ArrayList<Node> generatePath(Node startNode, Node endNode) {
ArrayList<Node> path = new ArrayList<Node>();
Node currentNode = endNode;
while(currentNode != startNode){
path.add(currentNode);
currentNode = currentNode.parent;
}
return path;
}
private Node findBestNode(ArrayList<Node> open) {
int lowF = 10000;
Node currentNode = null;
for (int i = 0 ; i<open.size() ; i++){
if(open.get(i).fscore < lowF){
lowF = open.get(i).fscore;
currentNode = open.get(i);
}
}
return currentNode;
}
private int getF(int sx, int sy, int tx, int ty){
int dx = Math.abs(tx - sx);
int dy = Math.abs(ty - sy);
int f = dx+dy;
return f;
}
private ArrayList<Node> getAdj(Node node){
ArrayList<Node> adj;
adj = new ArrayList<Node>();
for (int y = -1; y<2; y++){
for (int x = -1; x<2; x++){
if(node.x+x>-1 && node.y+y>-1){
Node theNode = nodes.get(tileNum(node.x+x, node.y+y));
//adj.add(theNode);
System.out.println(theNode);
adj.add(theNode);
}
}
}
return adj;
}
}
public class Game {
public Game() {
GameMap gm = new GameMap(640,360);
gm.blockNode(63, 32);
System.out.println(gm.findPath(0, 0, 4, 2));
}
public static void main(String[] args){
Game game = new Game();
}
}
希望我没有咬得太多。我正在尝试创建节点周围所有相邻节点的数组列表。错误可能是您调用：
currentNode = findBestNode(open);
这导致了一个NullPointerException..我已经尝试重写getAdj的代码4到5次了，我得到了相同的结果。我不明白为什么会发生这种情况。据我所知，node.x没有值，node.y没有值，但如果我不向adj arraylist添加任何内容，代码就会工作。它是nx或y节点为空..提示原语不能抛出空指针检查我不明白的是节点如何可能为空..这不像我改变了节点，代码工作到某一点，这里是我运行时的输出，它显示节点正在工作，但突然被空阻止节点2111 ericm.map。Node@e80317埃里克地图.Node@22e3ac埃里克·梅普。Node@916ab8埃里克·梅普。Node@f55759线程主java.lang.NullPointerException位于ericm.map.GameMap.getAdjGameMap.java:129位于ericm.map.GameMap.findPathGameMap.java:51位于ericm.game.game.game.java:11位于ericm.game.game.mainGame.java:16所以它基本上知道它周围的节点，但不会将它们添加到rraylist一旦退出for循环，如果没有打开的节点会发生什么？谢谢！我不得不调整一些事情，我终于让它工作了！
currentNode = findBestNode(open);