崩溃：com.badlogic.gdx.physics.box2d.World.jniCreateBody

Question

我在尝试游戏时 java 运行时环境发生 EXCEPTION_ACCESS_VIOLATION 崩溃。它是用 LibGdx 编写的（并使用 box2d）。它是运行来自 android 工作室的桌面模式。

我在我的超级马里奥游戏中添加了一个 "fireball" 功能，在跳入空中并发射火球时出现此错误。这是崩溃日志：

Java frames: (J=compiled Java code, j=interpreted, Vv=VM code) j com.badlogic.gdx.physics.box2d.World.jniCreateBody(JIFFFFFFFFZZZZZF)J+0 j com.badlogic.gdx.physics.box2d.World.createBody(Lcom/badlogic/gdx/physics/box2d/BodyDef;)Lcom/badlogic/gdx/physics/box2d/Body;+80 j com.mygdx.game.sprite.Fireball.define()V+68 j com.mygdx.game.sprite.Fireball.(Lcom/mygdx/game/screen/PlayScreen;FFZ)V+135 j com.mygdx.game.sprite.Mario.shootFire()V+36 J 1115 C1 com.mygdx.game.screen.PlayScreen.handleInput(F)V (221 bytes) @ 0x000000000320f90c [0x000000000320e960+0xfac] J 1073 C1 com.mygdx.game.screen.PlayScreen.update(F)V (188 bytes) @ 0x00000000031e14ec [0x00000000031e1440+0xac] J 1074 C1 com.mygdx.game.screen.PlayScreen.render(F)V (252 bytes) @ 0x00000000031e493c [0x00000000031e3f20+0xa1c] J 1223 C1 com.mygdx.game.MarioBros.render()V (5 bytes) @ 0x0000000003263ae4 [0x0000000003263920+0x1c4] j com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop()V+698 j com.badlogic.gdx.backends.lwjgl.LwjglApplication.run()V+27 v ~StubRoutines::call_stub

这是我的火球 class:

public class Fireball extends Sprite {

private PlayScreen playScreen;
private World world;
private Array<TextureRegion> frames;
private Animation<TextureRegion> animation;
private float stateTimer;
private boolean destroyed;
private boolean destroy;
private boolean fireToRight;
private Body body;

public Fireball(PlayScreen playScreen, float x, float y, boolean fireToRight){
    this.playScreen = playScreen;
    this.fireToRight = fireToRight;
    this.world = playScreen.getWorld();
    destroy = false;
    destroyed = false;
    frames = new Array<TextureRegion>();
    for(int i = 0; i < 4; i++)
        frames.add(new TextureRegion(playScreen.getAtlas().findRegion("fireball"),i*8,0,8,8));
    animation = new Animation<TextureRegion>(0.2f, frames);
    setRegion(animation.getKeyFrame(0));
    setBounds(x, y, 6/ C.PIXEL_PER_METER, 6/C.PIXEL_PER_METER);
    define();
}

private void define(){
    BodyDef bodyDef = new BodyDef();
    bodyDef.position.set(fireToRight ? getX() + 12 /C.PIXEL_PER_METER : getX() - 12 /C.PIXEL_PER_METER, getY());
    bodyDef.type = BodyDef.BodyType.DynamicBody;
    if(world.isLocked())
        return;
    body = world.createBody(bodyDef);
    FixtureDef fixtureDef = new FixtureDef();
    CircleShape shape = new CircleShape();
    shape.setRadius(3 / C.PIXEL_PER_METER);
    fixtureDef.filter.categoryBits = C.FIREBALL_BIT;
    fixtureDef.filter.maskBits = C.GROUND_BIT |
            C.COIN_BIT |
            C.BRICK_BIT |
            C.ENEMY_BIT |
            C.OBJECT_BIT;
    fixtureDef.shape = shape;
    fixtureDef.restitution = 1;
    fixtureDef.friction = 0;
    body.createFixture(fixtureDef).setUserData(this);
    body.setLinearVelocity(new Vector2(fireToRight ? 2 : -2, 2.5f));
}

public void update(float deltaTime){
    if((stateTimer > 3 || destroy) && !destroyed){
        world.destroyBody(body);
        destroyed = true;
        body = null;
        return;
    }

    stateTimer += deltaTime;
    setRegion(animation.getKeyFrame(stateTimer, true));
    setPosition(body.getPosition().x - getWidth()/2, body.getPosition().y - getHeight()/2);

    if(body.getLinearVelocity().y > 2f)
        body.setLinearVelocity(body.getLinearVelocity().x,2f);
    if((fireToRight && body.getLinearVelocity().x < 0 ) || (!fireToRight && body.getLinearVelocity().x > 0))
        destroy();
}

public void destroy(){
    destroy = true;
}

public boolean isDestroyed(){
    return destroyed;
}

}

我从 PlayScreen class 调用 mario.shootFire()。

这就是 "mario shoots fireballs" 的方式：

private Array<Fireball> fireballs;

fireballs = new Array<Fireball>();

 public void shootFire(){
        fireballs.add(new Fireball(playScreen, body.getPosition().x, body.getPosition().y, runRight));
    }

    @Override
    public void draw(Batch batch) {
        super.draw(batch);
        for (Fireball fireball: fireballs)
            fireball.draw(batch);
    }

关于我为什么会收到此错误的任何想法？

编辑：它似乎在 Fireball 的 define() 方法中的这一行 body = world.createBody(bodyDef) 处崩溃。

Answer 1

com.badlogic.gdx.physics.box2d.World.jniCreateBody

您正在尝试访问不再可用的内存。有几个关于如何在 box2d 中创建和销毁物体的教程。关于更新物理世界 (step())，您必须在正确的时间执行此操作。

因为你只得到 JNI 调试信息，所以很难准确知道错误在哪里（已经出现过很多次）获得更好异常的一个好方法是将主体设置为 null（紧接 world.destroyBody(正文);)

world.destroyBody(body);
body = null;
destroyed = true;

崩溃：com.badlogic.gdx.physics.box2d.World.jniCreateBody

CRASH: com.badlogic.gdx.physics.box2d.World.jniCreateBody

java

android

box2d

libgdx