java - Box2D 碰撞时将物体移动到不同的位置

Question

我有两个主体，一个动态主体和一个运动主体。当它们相互碰撞时，我想改变运动体的位置。我添加了一个接触监听器，并且能够检测到碰撞。但是当我想要改变运动体的变换时，我的游戏崩溃了。我非常感谢您的帮助。

错误:AL lib:(EE) alc_cleanup:1 个设备未关闭断言失败!

程序:D:\Program Files\Android\Android Studio\jre\bin\java.exe文件:/var/jenkins/.jenkins/workspace/libgdx/extensions/gdx-box2d/gdx-box2d/jni/Box2D/Dynamics/b2Body.cpp，第 419 行

表达式:m_world->IsLocked() == false

public class Player extends Sprite {
public static final float scale = 12;
public static final float moveSpeed = 110;
public Body b2body;

public Player(World world) {
    super(new Texture("playercut.jpg"));
    setBounds(0,0,getWidth() / (FishAdventureMain.PPM * Player.scale), getHeight() / (FishAdventureMain.PPM * Player.scale));
    BodyDef bdef = new BodyDef();
    PolygonShape shape = new PolygonShape();
    FixtureDef fdef = new FixtureDef();
    bdef.type = BodyDef.BodyType.DynamicBody;
    bdef.position.set(650/FishAdventureMain.PPM, 200 / FishAdventureMain.PPM);
    b2body = world.createBody(bdef);
    shape.setAsBox(getWidth() / 3, getHeight() / 5);
    fdef.shape = shape;
    b2body.createFixture(fdef).setUserData("head");
}

public void update() {
    super.setPosition(b2body.getPosition().x - getWidth()/2, (b2body.getPosition().y - getHeight()/2) + (float)Math.sin(System.currentTimeMillis() * 0.009) * 0.04f);
}

}

public class AbstractGameObj {
protected final float moveSpeed = 90;
private Sprite sprite;
protected World world;
protected Body body;
protected Fixture fixture;
protected Vector2 position;

public AbstractGameObj(World world, Sprite sprite, Vector2 position, float scaleFactor1, float scaleFactor2) {
    this.world = world;
    this.sprite = sprite;
    this.position = position;

    BodyDef bdef = new BodyDef();
    PolygonShape shape = new PolygonShape();
    FixtureDef fdef = new FixtureDef();
    bdef.position.set(position);
    bdef.type = BodyDef.BodyType.KinematicBody;
    body = world.createBody(bdef);
    shape.setAsBox(sprite.getWidth() / scaleFactor1, sprite.getHeight() / scaleFactor2);
    fdef.shape = shape;
    fixture = body.createFixture(fdef);
}
public void update(float dt) {
    sprite.setPosition(body.getPosition().x - sprite.getWidth()/2, body.getPosition().y - sprite.getWidth() / 2);
    body.setLinearVelocity(moveSpeed *dt, 0);
}
public void onCollision() {

}
public Sprite getSprite() { return this.sprite; }

}

public class Coconut extends AbstractGameObj{

public Coconut(World world, Sprite sprite, Vector2 position, float scaleFactor1, float scaleFactor2) {
    super(world, sprite, position, scaleFactor1, scaleFactor2);
    fixture.setUserData(this);
}

@Override
public void onCollision() {
    body.setTransform(100, 100, body.getAngle());
}

}

public class B2WorldCreator {

private Sprite cocoSprite1;
private Sprite cocoSprite2;

private Array<Coconut> cocoNuts;

public B2WorldCreator(World world) {
    //Border bottom
    BodyDef bdef = new BodyDef();
    PolygonShape shape = new PolygonShape();
    FixtureDef fdef = new FixtureDef();

    bdef.type = BodyDef.BodyType.StaticBody;
    bdef.position.set(0, 0);
    shape.setAsBox(FishAdventureMain.V_WIDTH / FishAdventureMain.PPM, 1 / FishAdventureMain.PPM);
    fdef.shape = shape;
    world.createBody(bdef).createFixture(fdef);

    //Border Top
    bdef.type = BodyDef.BodyType.StaticBody;
    bdef.position.set(0, FishAdventureMain.V_HEIGHT / FishAdventureMain.PPM);
    shape.setAsBox(FishAdventureMain.V_WIDTH / FishAdventureMain.PPM, 1 / FishAdventureMain.PPM);
    fdef.shape = shape;
    world.createBody(bdef).createFixture(fdef);

    //Border left
    bdef.type = BodyDef.BodyType.StaticBody;
    bdef.position.set(FishAdventureMain.V_WIDTH / FishAdventureMain.PPM, FishAdventureMain.V_HEIGHT / FishAdventureMain.PPM);
    shape.setAsBox(1 / FishAdventureMain.PPM, FishAdventureMain.V_HEIGHT / FishAdventureMain.PPM);
    fdef.shape = shape;
    world.createBody(bdef).createFixture(fdef);

    //Border kind of middle
    bdef.type = BodyDef.BodyType.StaticBody;
    bdef.position.set(200 / FishAdventureMain.PPM, 0);
    shape.setAsBox(1 / FishAdventureMain.PPM, FishAdventureMain.V_HEIGHT / FishAdventureMain.PPM);
    fdef.shape = shape;
    world.createBody(bdef).createFixture(fdef);

    //Coconuts
    cocoNuts = new Array<Coconut>();
    cocoSprite1 = new Sprite(new Texture("coconut.jpg"));
    cocoSprite1.setBounds(0,0, cocoSprite1.getWidth() / FishAdventureMain.PPM/10, cocoSprite1.getHeight() / FishAdventureMain.PPM/10);
    cocoSprite2 = new Sprite(new Texture("coconut.jpg"));
    cocoSprite2.setBounds(0,0, cocoSprite2.getWidth() / FishAdventureMain.PPM/10, cocoSprite2.getHeight() / FishAdventureMain.PPM/10);
    cocoNuts.add(new Coconut(world, cocoSprite1, new Vector2(-300 / FishAdventureMain.PPM, 2), 1.8f, 1.8f));
    cocoNuts.add(new Coconut(world, cocoSprite2, new Vector2(-1800 / FishAdventureMain.PPM, 2), 1.8f, 1.8f));

}
public void updateCocoNuts(float dt) {
    for (Coconut nut : cocoNuts) {
        nut.update(dt);
    }
}
public void showCocoNuts(SpriteBatch sb) {
    for (Coconut nut : cocoNuts) {
        nut.getSprite().draw(sb);
    }
}

}

public class PlayScreen extends InputAdapter implements Screen {
private FishAdventureMain main;
private OrthographicCamera gameCam;
private Viewport gamePort;
private Hud hud;
private ButtonController bcont;
private Texture background;
private World world;
private Box2DDebugRenderer renderer;
private Player player;
private B2WorldCreator creator;

public PlayScreen(FishAdventureMain main) {
    this.main = main;
    gameCam = new OrthographicCamera();
    gamePort = new StretchViewport(FishAdventureMain.V_WIDTH / FishAdventureMain.PPM, FishAdventureMain.V_HEIGHT / FishAdventureMain.PPM, gameCam);
    hud = new Hud(main.batch);
    bcont = new ButtonController(main.batch);
    background = new Texture("background.jpg");
    world = new World(new Vector2(0, 0), true);
    creator = new B2WorldCreator(world);
    renderer = new Box2DDebugRenderer();
    player = new Player(world);
    gameCam.position.set(gamePort.getWorldWidth()/2, gamePort.getWorldHeight()/2,0);
    world.setContactListener(new ContactListener() {
        @Override
        public void beginContact(Contact contact) {
            Fixture fixA = contact.getFixtureA();
            Fixture fixB = contact.getFixtureB();

            if (fixA.getUserData() == "head" || fixB.getUserData() == "head") {
                Fixture head = fixA.getUserData() == "head" ? fixA : fixB;
                Fixture object = head == fixA ? fixB : fixA;
                if (object.getUserData() != null && AbstractGameObj.class.isAssignableFrom(object.getUserData().getClass())) {
                    ((AbstractGameObj) object.getUserData()).onCollision();
                }
            }
        }

        @Override
        public void endContact(Contact contact) {

        }

        @Override
        public void preSolve(Contact contact, Manifold oldManifold) {

        }

        @Override
        public void postSolve(Contact contact, ContactImpulse impulse) {

        }
    });
}

@Override
public void show() {
    Gdx.gl.glClearColor(0, 0,0,1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

    main.batch.setProjectionMatrix(gamePort.getCamera().combined);
    main.batch.begin();
    main.batch.draw(background, 0, 0, FishAdventureMain.V_WIDTH / FishAdventureMain.PPM, FishAdventureMain.V_HEIGHT / FishAdventureMain.PPM);
    player.draw(main.batch);
    creator.showCocoNuts(main.batch);
    main.batch.end();
    renderer.render(world, gameCam.combined);

    main.batch.setProjectionMatrix(hud.stage.getCamera().combined);
    hud.stage.draw();
    bcont.stage.draw();
}

@Override
public void render(float delta) {
    update(delta);
    show();
}

public void update(float dt) {
    handleInput(dt);
    world.step(1/60f, 6, 2);
    gameCam.update();
    player.update();
    creator.updateCocoNuts(dt);
}

private void handleInput(float dt) {
    if (bcont.getUpPressed())
        player.b2body.setLinearVelocity(new Vector2(player.b2body.getLinearVelocity().x, Player.moveSpeed * dt));
    else if (bcont.getDownPressed())
        player.b2body.setLinearVelocity(new Vector2(player.b2body.getLinearVelocity().x, -Player.moveSpeed * dt));
    else
        player.b2body.setLinearVelocity(player.b2body.getLinearVelocity().x, 0);
    if(bcont.getLeftPressed())
        player.b2body.setLinearVelocity(new Vector2(-Player.moveSpeed * dt, player.b2body.getLinearVelocity().y));
    else if (bcont.getRightPressed())
        player.b2body.setLinearVelocity(new Vector2(Player.moveSpeed * dt, player.b2body.getLinearVelocity().y));
    else
        player.b2body.setLinearVelocity(new Vector2(0, player.b2body.getLinearVelocity().y));
}

@Override
public void resize(int width, int height) {
    gamePort.update(width, height);
}

@Override
public void pause() {

}

@Override
public void resume() {

}

@Override
public void hide() {

}

@Override
public void dispose() {
    background.dispose();
    hud.dispose();
}

}

Answer 1

您遇到的问题是您试图在物理处理过程中移动对象。 Box2D 不喜欢在物理处理期间(例如在碰撞期间)移动或更改对象

为了解决这个问题，您必须为碰撞对象设置一个标志，然后在物理完成后移动它。

例如

// during physics processing
@Override
public void onCollision() {
    //add body to array of objects to move
}

然后添加

 public void update(float dt) {
    handleInput(dt);
    world.step(1/60f, 6, 2);
    // world is done processing physics
    // loop through array and move objects
    gameCam.update();
    player.update();
    creator.updateCocoNuts(dt);
}