时间戳

首页 > 解决方案 > 无缘无故得到 NullPointerException

java - 无缘无故得到 NullPointerException

问题描述

我无缘无故地收到 NullPointerException。请不要将我重定向到另一个帖子。我都看过了。我正在用 LibGDX 制作游戏。

这是错误

Exception in thread "LWJGL Application" java.lang.NullPointerException
    at net.hasanbilal.pr.entities.Entity.getWeight(Entity.java:88)
    at net.hasanbilal.pr.entities.Entity.update(Entity.java:25)
    at net.hasanbilal.pr.entities.Porter.update(Porter.java:34)
    at net.hasanbilal.pr.world.GMap.update(GMap.java:28)
    at net.hasanbilal.pr.world.TiledGMap.update(TiledGMap.java:40)
    at net.hasanbilal.pr.PrisonRevelations.render(PrisonRevelations.java:59)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:215)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:120)

我将向每个班级展示错误点。

这是实体类。

package net.hasanbilal.pr.entities;

import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.math.Vector2;

import net.hasanbilal.pr.world.GMap;

public abstract class Entity {

    protected Vector2 pos;
    protected EntityType t;
    protected float velocityY = 0;
    protected GMap m;
    protected boolean grounded = false;

    public void create (EntitySnapshot snapshot, EntityType type, GMap map) {
        this.pos = new Vector2(snapshot.getX(),snapshot.getY());
        this.t = t;
        this.m = m;
    }

    public void update (float delta, float g) {
        float newY = pos.y;

        this.velocityY += g * delta * getWeight();
        newY += this.velocityY * delta;

        if (m.doesRectCollideWithMap(pos.x, newY, getWidth(), getHeight())) {
            if (velocityY < 0) {
                this.pos.y = (float) Math.floor(pos.y);
                grounded = true;
            }
            this.velocityY = 0;
        } else {
            this.pos.y = newY;
            grounded = false;
        }


    }

    public abstract void render (SpriteBatch b);


    protected void moveX(float amount) {
        float newX = this.pos.x + amount;
        if (!m.doesRectCollideWithMap(newX, pos.y, getWidth(), getHeight()))
            this.pos.x = newX;
    }

    public EntitySnapshot getSaveSnapshot(){
        return new EntitySnapshot(t.getId(), pos.x, pos.y);
    }

    public Vector2 getPos() {
        return pos;
    }

    public float getX() {
        return pos.x;
    }

    public float getY() {
        return pos.y;
    }

    public EntityType getT() {
        return t;
    }

    public float getVelocityY() {
        return velocityY;
    }

    public boolean isGrounded() {
        return grounded;
    }

    public int getWidth() {
        return t.getWidth();
    }

    public int getHeight() {
        return t.getHeight();
    }

    public float getWeight() {
        return t.getWeight();
    }


}

这是波特班。

package net.hasanbilal.pr.entities;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Input.Keys;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

import net.hasanbilal.pr.world.GMap;

public class Porter extends Entity {

    private static final int SPEED = 80;
    private static final int JUMP_VELOCITY = 5;
    Texture img;

    public void create (EntitySnapshot snapshot, EntityType type, GMap map) {
        super.create(snapshot, type, map);
        img = new Texture("porter.png");

    }

    @Override
    public void render(SpriteBatch b) {
        b.draw(img, pos.x, pos.y, getWidth(), getHeight());

    }

    public void update(float delta, float g) {
        if (Gdx.input.isKeyPressed(Keys.SPACE) && grounded)
            this.velocityY += JUMP_VELOCITY * getWeight();
        else if (Gdx.input.isKeyPressed(Keys.SPACE) && !grounded && this.velocityY > 0)
            this.velocityY += JUMP_VELOCITY * getWeight() * delta;

        super.update(delta, g);

        if (Gdx.input.isKeyPressed(Keys.LEFT))
            moveX(-SPEED * delta);

        if (Gdx.input.isKeyPressed(Keys.RIGHT))
            moveX(SPEED * delta);
    }


}

这是GMap

package net.hasanbilal.pr.world;

import java.util.ArrayList;

import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

import net.hasanbilal.pr.entities.Entity;
import net.hasanbilal.pr.entities.EntityLoader;
import net.hasanbilal.pr.entities.Porter;

public abstract class GMap {

    protected ArrayList<Entity> entities;

    public GMap() {
        entities = new ArrayList<Entity>();
        entities.addAll(EntityLoader.loadEntities("basic", this, entities));
    }

    public void render (OrthographicCamera c, SpriteBatch b) {
        for (Entity entity : entities) {
            entity.render(b);
        }
    }
    public void update (float deltaTime) {
        for (Entity entity : entities) {
            entity.update(deltaTime, -9.8f);
        }
    }
    public void dispose () {
        EntityLoader.saveEntities("basic", entities);
    }

    /**
     * Gets a tile by location
     * @param layer
     * @param x
     * @param y
     * @return
     */
    public TileType getByLocation(int layer, float x, float y) {
        return this.getByCoordinate(layer, (int) (x / TileType.TILE_SIZE), (int) (y / TileType.TILE_SIZE));
    }

    /**
     * Gets Tile by coordinate
     * @param layer
     * @param col
     * @param row
     * @return
     */
    public abstract TileType getByCoordinate(int layer, int col, int row);

    public boolean doesRectCollideWithMap(float x, float y, int width, int height) {
        if (x<0 || y < 0 || x + width > getPixelWidth() || y + height > getPixelHeight())
            return true;

        for (int row = (int) (y / TileType.TILE_SIZE); row < Math.ceil((y + height) / TileType.TILE_SIZE); row++) {
            for (int col = (int) (x / TileType.TILE_SIZE); col < Math.ceil((x + width) / TileType.TILE_SIZE); col++) {
                for (int layer = 0; layer < getLayers(); layer++) {
                    TileType type = getByCoordinate(layer, col, row);
                    if (type != null && type.isCollidable())
                        return true;
                }
            }
        }
        return false;
    }

    public abstract int getWidth();
    public abstract int getHeight();
    public abstract int getLayers();

    public int getPixelWidth() {
        return this.getWidth() * TileType.TILE_SIZE;
    }

    public int getPixelHeight() {
        return this.getHeight() * TileType.TILE_SIZE;
    }

}

这是 TiledGMap 的类

package net.hasanbilal.pr.world;

import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.maps.tiled.TiledMap;
import com.badlogic.gdx.maps.tiled.TiledMapTile;
import com.badlogic.gdx.maps.tiled.TiledMapTileLayer;
import com.badlogic.gdx.maps.tiled.TiledMapTileLayer.Cell;
import com.badlogic.gdx.maps.tiled.TmxMapLoader;
import com.badlogic.gdx.maps.tiled.renderers.OrthogonalTiledMapRenderer;

import net.hasanbilal.pr.entities.Entity;
import net.hasanbilal.pr.entities.Porter;

public class TiledGMap extends GMap {

    TiledMap lvl1;
    OrthogonalTiledMapRenderer otmr;

    public TiledGMap() {
        lvl1 = new TmxMapLoader().load("level1.tmx");
        otmr = new OrthogonalTiledMapRenderer(lvl1);
    }


    @Override
    public void render(OrthographicCamera c, SpriteBatch b) {
        otmr.setView(c);
        otmr.render();

        b.setProjectionMatrix(c.combined);
        b.begin();
        super.render(c, b);
        b.end();

    }

    @Override
    public void update(float deltaTime) {
        super.update(deltaTime);

    }

    @Override
    public void dispose() {
        lvl1.dispose();

    }

    @Override
    public TileType getByCoordinate(int layer, int col, int row) {
        Cell cell  = ((TiledMapTileLayer) lvl1.getLayers().get(layer)).getCell(col, row);

        if (cell !=null) {
            TiledMapTile t = cell.getTile();

            if (t != null) {
                int id = t.getId();
                return TileType.getTileTypeById(id);
            }
        }
        return null;
    }

    @Override
    public int getWidth() {

        return ((TiledMapTileLayer) lvl1.getLayers().get(0)).getWidth();
    }

    @Override
    public int getHeight() {

        return ((TiledMapTileLayer) lvl1.getLayers().get(0)).getHeight();
    }

    @Override
    public int getLayers() {

        return lvl1.getLayers().getCount();
    }

}

这是监狱启示录课程

package net.hasanbilal.pr;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.math.Vector3;

import net.hasanbilal.pr.world.GMap;
import net.hasanbilal.pr.world.TileType;
import net.hasanbilal.pr.world.TiledGMap;

public class PrisonRevelations extends ApplicationAdapter {

    OrthographicCamera c;
    SpriteBatch b;

    GMap gm;

    @Override

    public void create () {
        b = new SpriteBatch();

        c = new OrthographicCamera();
        c.setToOrtho(false, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
        c.update();
        gm = new TiledGMap();



    }

    @Override
    public void render () {
        Gdx.gl.glClearColor(255, 255, 255, 1);
        Gdx.gl.glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);



        if (Gdx.input.isTouched()) {
            c.translate(-Gdx.input.getDeltaX(), Gdx.input.getDeltaY());
            c.update();
        }

        if (Gdx.input.justTouched()) {
            Vector3 pos = c.unproject(new Vector3(Gdx.input.getX(), Gdx.input.getY(), 0));
            TileType t = gm.getByLocation(1, pos.x, pos.y);

            if (t != null) {
                System.out.println("You clicked on tile with id" + t.getId() + " " + t.getName()+ " " + t.isCollidable() + " " + t.getDamage());
            }
        }

        c.update();
        gm.update(Gdx.graphics.getDeltaTime());
        gm.render(c, b);
    }

    @Override
    public void dispose () {
        b.dispose();
        gm.dispose();
    }
}

请帮忙。我要死了。这很快就要到期了。

标签： javalibgdx

解决方案

看起来你在创建参数名称时犯了一个错误，更改为：

public void create (EntitySnapshot snapshot, EntityType type, GMap map) {
    this.pos = new Vector2(snapshot.getX(),snapshot.getY());
    this.t = type;
    this.m = map;
}

推荐阅读