Java LibGDX 无法在启用物理体和重力的情况下移动

Question

我真的需要一些帮助我坚持这个。我试图在一个简单的游戏中让一个方块成为地面，另一个方块落在上面然后可能会反弹一点但能够向左或向右移动盒子以从第一个方块上掉下来。谁能帮我解决这个问题？

对于任何对答案感兴趣的人，感谢 PoprostuRonin 和 dermetfan 的 YouTube 视频，我能够得到我正在寻找的结果，你可以在你的项目中尝试下面的代码，只需更改精灵纹理。

private Box2DDebugRenderer debugRenderer;
private OrthographicCamera camera;
private float spriteSpeed = 500000;
private World world;
private Sprite playersprite;
private Sprite groundsprite;
private Body playerBody;
private Body groundbody;
private Vector2 movement = new Vector2();
private Array<Body> tmpBodies = new Array<Body>();

public TestState(GameStateManager gsm) {
    super(gsm);

    Gdx.input.setInputProcessor(this);

    batch = new SpriteBatch();

    debugRenderer = new Box2DDebugRenderer();
    camera = new OrthographicCamera();

    // Sprites
    playersprite = new Sprite(new Texture("badlogic.jpg"));
    groundsprite = new Sprite(new Texture("ground-tiles-01.gif"));

    // World
    world = new World(new Vector2(0, -9.8f), true);

    // Player Sprite
    // Body definition
    BodyDef bodyDef = new BodyDef();
    bodyDef.type = BodyType.DynamicBody;
    bodyDef.position.set(0, 200); //1m

    PolygonShape shape = new PolygonShape();
    shape.setAsBox(10, 10);

    // Fixture definition
    FixtureDef fixtureDef = new FixtureDef();
    fixtureDef.shape = shape;
    fixtureDef.density = 2.5f; //2.5kg
    fixtureDef.friction = 0; //0-1
    fixtureDef.restitution = .75f; //0-1

    playerBody = world.createBody(bodyDef); 
    playerBody.createFixture(fixtureDef);
    playerBody.setUserData(playersprite);
    playersprite.setSize(20, 20);
    playersprite.setOrigin(playersprite.getWidth() / 2, playersprite.getHeight() / 2);
    shape.dispose();

    // Ground Sprite
    // Body definition
    BodyDef groundbodyDef = new BodyDef();
    groundbodyDef.type = BodyType.StaticBody;
    groundbodyDef.position.set(0, 0); //1m

    PolygonShape groundshape = new PolygonShape();
    groundshape.setAsBox(groundsprite.getHeight() / 2, groundsprite.getWidth() / 2);

    // Fixture definition
    FixtureDef groundfixtureDef = new FixtureDef();
    groundfixtureDef.shape = groundshape;
    groundfixtureDef.density = 100; //2.5kg
    groundfixtureDef.friction = .25f; //0-1
    groundfixtureDef.restitution = 0; //0-1

    groundbody = world.createBody(groundbodyDef); 
    groundbody.createFixture(groundfixtureDef);
    groundbody.setUserData(groundsprite);
    groundsprite.setSize(groundsprite.getHeight(), groundsprite.getWidth());
    groundsprite.setOrigin(groundsprite.getWidth() / 2, groundsprite.getHeight() / 2);

    groundshape.dispose();
}

@Override
public void update(float delta) {
    camera.viewportWidth = Gdx.graphics.getWidth();
    camera.viewportHeight = Gdx.graphics.getHeight();
}

@Override
public void render() {
    Gdx.gl.glClearColor(50 / 255f, 213 / 255f, 237 / 255f, 1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

    debugRenderer.render(world, camera.combined);
    batch.setProjectionMatrix(camera.combined);
    world.step(Gdx.graphics.getDeltaTime(), 6, 2);

    playerBody.applyForceToCenter(movement, true);

    batch.begin();
    world.getBodies(tmpBodies);
    for (Body body : tmpBodies){
        if (body.getUserData() != null && body.getUserData() instanceof Sprite) {
            Sprite sprite = (Sprite) body.getUserData();
            sprite.setPosition(body.getPosition().x - sprite.getWidth() / 2, body.getPosition().y - sprite.getHeight() / 2);
            sprite.setRotation(body.getAngle() * MathUtils.radiansToDegrees);
            sprite.draw(batch);
        }
    }
    batch.end();

    camera.position.set(playerBody.getPosition().x, playerBody.getPosition().y, 0);
    camera.update();

}

@Override
public void dispose() {
    world.dispose();
    playersprite.getTexture().dispose();
    groundsprite.getTexture().dispose();
}

@Override
public boolean keyDown(int keycode) {
    switch (keycode) {
    case Keys.DPAD_LEFT:
        movement.x = -spriteSpeed;
        break;
    case Keys.DPAD_RIGHT:
        movement.x = spriteSpeed;
        break;
    case Keys.DPAD_UP:
        movement.y = spriteSpeed;
        break;
    case Keys.DPAD_DOWN:
        movement.y = -spriteSpeed;
    }
    return true;
}

@Override
public boolean keyUp(int keycode) {
    switch (keycode) {
    case Keys.DPAD_LEFT:
    case Keys.DPAD_RIGHT:
        movement.x = 0;
        break;
    case Keys.DPAD_UP:
    case Keys.DPAD_DOWN:
        movement.y = 0;
    }
    return true;
}

Answer 1

你的代码是有效的，问题是数字。

你的body体重很大，20480kg。重力反转是因为您要求它：

world = new World(new Vector2(0, -1000f), true);

-1000，它小于 0，所以它是倒置的，并且是一个大数字（在你的 "planet" 上是 1000，在地球上是 9.8）导致 object 难以控制。

更改值：

float spriteSpeed = 60000;
...
world = new World(new Vector2(0, 9.8F), true);
...
fixtureDef.density = 1;
fixtureDef2.density = 1;

你会注意到现在 body 是可控的（它甚至可以飞行）。玩弄这些数字并学习一些基本的物理规则以了解您在做什么。

精灵和 body 位置已同步，但未正确对齐。使用此代码进行第一步，使纹理与 body.

对齐

sprite.setCenter(body.getPosition().x, body.getPosition().y);
groundsprite.setCenter(ground.getPosition().x, ground.getPosition().y);

但是旋转呢

groundsprite.setOriginCenter();
sprite.setOriginCenter();

groundsprite.setRotation(ground.getAngle() * MathUtils.radDeg);
sprite.setRotation(body.getAngle() * MathUtils.radDeg);

这很简单，因为您的 object 是单个纹理，我们可以简单地将其居中对齐，但是随着 object 变得更加复杂，需要更改代码。

Java LibGDX 无法在启用物理体和重力的情况下移动

Java LibGDX cannot move with physics bodies and gravity enabled

java

box2d

libgdx