好的，我正在构建一个 Java 游戏 (RPG)，并且我正在使用一个图块集。现在我想让我的角色一个接一个地行走并构建一个代码，只有当我按下行走按钮时它会返回一个 Thread 3 NullPointerException ..
这是它给我的错误：”
Exception in thread "Thread-3" java.lang.NullPointerException
at net.chosensentinel.dvdv.EntityPlayer.canMove(EntityPlayer.java:152)
at net.chosensentinel.dvdv.EntityPlayer.move(EntityPlayer.java:48)
at net.chosensentinel.dvdv.Core.tick(Core.java:70)
at net.chosensentinel.dvdv.Core.run(Core.java:141)
at java.lang.Thread.run(Unknown Source)
每个类和方法（据我所知）都以良好的方式被调用。
代码构建：
核：
package net.chosensentinel.dvdv;
import java.applet.Applet;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
public class Core extends Applet implements Runnable{
private static final long serialVersionUID = 1L;
private static JFrame frame;
public static final int res = 1;
public final int TARGET_FPS = 60;
public final long OPTIMAL_TIME = 1000000000/TARGET_FPS;
public static long lastFpsTime = 0;
public static int fps = 0;
public static int renderFps = 0;
public static double oY = 0, oX = 0;
public static int dir = 0;
public static boolean moving = false;
public static boolean run = false;
private Image screen;
private ArrayList<Entity> entities = new ArrayList<Entity>();
private ArrayList<Entity> removeList = new ArrayList<Entity>();
public static EntityPlayer player;
public static boolean bW, bS, bA, bD, bE, bSpace, bP;
public static boolean inGame = true;
public Level level;
public static Core core;
public static Dimension screenSize = new Dimension(700, 560);
public static Dimension pixel = new Dimension(screenSize.width, screenSize.height);
public static Dimension Size;
public static String name = "Dawn - The Chosen Sentinel";
public Core(){
setPreferredSize(screenSize);
addKeyListener(new InputManager());
initEntities();
}
public void tick(double delta){
frame.pack();
if(inGame){
for(int i = 0; i < entities.size(); i++) {
Entity entity = (Entity)entities.get(i);
entity.move(delta);
}
for(int i = 0; i < entities.size(); i++) {
for(int j = i + 1; j < entities.size(); j++){
Entity me = (Entity)entities.get(i);
Entity him = (Entity)entities.get(j);
if(me.collidesWith(him)){
me.collidedWith(him);
him.collidedWith(me);
}
}
}
entities.remove(removeList);
removeList.clear();
}
}
public void render(){
Graphics g = screen.getGraphics();
g.setColor(Color.black);
g.drawRect(0, 0, 800, 800);
level.render(g, (int)oX, (int)oY, (pixel.width / Tile.size) + 2, (pixel.height / Tile.size) +2);
for(int i = 0; i < entities.size(); i++) {
Entity entity = (Entity)entities.get(i);
entity.render(g);
}
g.setColor(Color.red);
g.drawString("FPS: " + renderFps, 600, 530);
g = this.getGraphics();
g.drawImage(screen, 0, 0, screenSize.width, screenSize.height, 0, 0, pixel.width, pixel.height, null);
g.dispose();
}
public void removeEntity(Entity entity){
removeList.add(entity);
}
public void initEntities(){
player = new EntityPlayer(core, (pixel.width / 2) - (Tile.size / 2) + oX, (pixel.height / 2) - (Tile.size / 2) + oY, 32, 32);
entities.add(player);
}
public void run() {
screen = createVolatileImage(pixel.width, pixel.height);
long lastLoopTime = System.nanoTime();
while(run){
long now = System. nanoTime();
long updateLength = now - lastLoopTime;
lastLoopTime = now;
double delta = updateLength / (double)OPTIMAL_TIME;
lastFpsTime += updateLength;
fps++;
if(lastFpsTime >= 1000000000){
renderFps = fps;
fps = 0;
lastFpsTime = 0;
}
tick(delta);
render();
try{
Thread.sleep((lastLoopTime - System.nanoTime() + OPTIMAL_TIME) / 1000000);
}catch(Exception e){}
}
}
public void start(){
requestFocus();
//define classes
level = new Level(1);
new Tile();
run = true;
new Thread(this).start();
}
public void stop(){
run = false;
}
public static void main(String[] args){
core = new Core();
frame = new JFrame();
frame.add(core);
frame.pack();
Size = new Dimension(frame.getWidth(), frame.getHeight());
frame.setTitle(name);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
core.start();
}
}
实体播放器：
package net.chosensentinel.dvdv;
import java.awt.Graphics;
import java.awt.Rectangle;
public class EntityPlayer extends Entity{
public double moveSpeed = 2;
private static int Rx, Ry;
public static int tX, tY;
public static boolean isMoving = false;
private static int moveDelta = 0;
private Core CS;
public int aniFrame = 0;
public int aniTime = 10;
public int aniDelta = 0;
public EntityPlayer(Core cS, double x, double y, int width, int height){
super(new int[] {0,0}, x, y, width, height);
Rx = (int)(x - CS.oX);
Ry = (int)(y - CS.oY);
CS = cS;
moveSpeed = 32;
health = 110;
}
@Override
public void move(double delta){
aniDelta ++;
if(aniDelta >= aniTime){
aniFrame ++;
aniDelta = 0;
if(aniFrame > 2){
aniFrame = 1;
}
}
//up
if(CS.bW){
if(canMove(tX, tY - 1)&& !isMoving){
isMoving = true;
tY -= 1;
}
if(!isMoving){
CS.bW = false;
}
if(isMoving){
CS.oY += moveSpeed;
moveDelta += moveSpeed;
if(moveDelta >= 32){
isMoving = false;
moveDelta = 0;
aniFrame = 0;
}
}
}
//down
if(CS.bS){
if(canMove(tX, tY + 1)&& !isMoving){
isMoving = true;
tY += 1;
}
if(!isMoving){
CS.bS = false;
}
if(isMoving){
CS.oY -= moveSpeed;
moveDelta += moveSpeed;
if(moveDelta >= 32){
isMoving = false;
moveDelta = 0;
aniFrame = 0;
}
}
}
//left
if(CS.bA){
if(canMove(tX - 1, tY)&& !isMoving){
isMoving = true;
tX -= 1;
}
if(!isMoving){
CS.bA = false;
}
if(isMoving){
CS.oX -= moveSpeed;
moveDelta += moveSpeed;
if(moveDelta >= 32){
isMoving = false;
moveDelta = 0;
aniFrame = 0;
}
}
}
//right
if(CS.bD){
if(canMove(tX + 1, tY)&& !isMoving){
isMoving = true;
tX += 1;
}
if(!isMoving){
CS.bD = false;
}
if(isMoving){
CS.oX += moveSpeed;
moveDelta += moveSpeed;
if(moveDelta >= 32){
isMoving = false;
moveDelta = 0;
aniFrame = 0;
}
}
}
}
@Override
public void render(Graphics g){
super.setImage(new int[]{0,0});
g.drawImage(image, Rx, Ry, null);
}
public boolean canMove(int i, int j){
if(CS.level.solid[i][j].id == Tile.blank){
return true;
}
return false;
}
public void collidedWith(Entity entity) {
}
}
等级：
package net.chosensentinel.dvdv;
import java.awt.Graphics;
import java.awt.Rectangle;
import org.newdawn.slick.SlickException;
import org.newdawn.slick.tiled.TiledMap;
public class Level {
public int width = 100, height = 100;
public Background[][] bg = new Background[width][height];
public Solid[][] solid = new Solid[width][height];
public Item[][] item = new Item[width][height];
public final String Dpath = "Res/World/Level_";
public String path = Dpath;
public TiledMap map = null;
public Level(int id){
path = Dpath + Integer.toString(id) + ".tmx";
System.out.println(path);
try{
map = new TiledMap(path, false);
}catch(SlickException e){
System.out.println("Error Loading Map!");
}
for(int x = 0; x < bg.length; x++){
for(int y = 0; y < bg[0].length; y++){
bg[x][y] = new Background(new Rectangle(x * Tile.size, y * Tile.size, Tile.size, Tile.size), Tile.blank);
solid[x][y] = new Solid(new Rectangle(x * Tile.size, y * Tile.size, Tile.size, Tile.size), Tile.blank);
item[x][y] = new Item(new Rectangle(x * Tile.size, y * Tile.size, Tile.size, Tile.size), Tile.blank);
}
}
loadWorld();
}
public void loadWorld(){
int background = map.getLayerIndex("background");
int solids = map.getLayerIndex("collision");
int items = map.getLayerIndex("object");
for(int x = 0; x < bg.length; x++){
for(int y = 0; y < bg[0].length; y++){
//Background
if(map.getTileId(x, y, background) == 1){
bg[x][y].id = Tile.grass;
}
if(map.getTileId(x, y, background) == 2){
bg[x][y].id = Tile.road;
}
if(map.getTileId(x, y, background) == 3){
bg[x][y].id = Tile.leaves;
}
//Solids
if(map.getTileId(x, y, solids) == 64){
solid[x][y].id = Tile.grass;
}
//Items
if(map.getTileId(x, y, items) == 129){
item[x][y].id = Tile.grass;
}
}
}
}
public void tick(double delta){
}
public void render(Graphics g, int camX, int camY, int renX, int renY){
for (int x = (camX / Tile.size); x < (camX / Tile.size) + renX; x++){
for (int y = (camY / Tile.size); y < (camY / Tile.size)+ renY; y++){
if(x >= 0 && y >= 0 && x < width && y < height){
bg[x][y].render(g);
}
}
}
}
}
这些是我正在使用的每个课程等。
我希望有人可以帮助我，让我的角色移动（只有移动，我会自己尝试动画:)）