我的body在创建Box2d LibGDX后下降了一点

Question

我正在创建一个用于练习的Arkanoid游戏。我有一个抽象的父类游戏对象，用于游戏精灵(蝙蝠、砖块、球(：

public abstract class GameObject extends Sprite {
protected World world;
protected Body body;
public GameObject(Texture texture, float width, float height, Vector2 centerPosition, World world) {
super(texture);
this.world = world;
setOrigin(width / 2, height / 2);
setSize(width, height);
setCenter(centerPosition.x, centerPosition.y);
defineBody();
}
public void render(float delta) {
setPosition(body.getPosition().x - getWidth() / 2, body.getPosition().y - getHeight() / 2);
draw(batch);
}
protected abstract void defineBody();
public Body getBody() {
return body;
}
}

我的蝙蝠：

public class Bat extends GameObject {
public Bat(World world) {
super(batTexture, BAT_WIDTH, BAT_HEIGHT, new Vector2(WORLD_WIDTH / 2, 5 + BAT_HEIGHT / 2), world);
}
public void moveLeft(float delta) {
body.getPosition().set(-BAT_MOVEMENT_SPEED * delta, 0);
checkForBoundaries();
}
public void moveRight(float delta) {
translateX(BAT_MOVEMENT_SPEED * delta);
checkForBoundaries();
}
private void checkForBoundaries() {
if (body.getPosition().x - getWidth() / 2 < 0) setX(getWidth() / 2);
else if (body.getPosition().x + getWidth() / 2 > WORLD_WIDTH) setX(WORLD_WIDTH - getWidth() / 2);
}
@Override
protected void defineBody() {
BodyDef bodyDef = new BodyDef();
bodyDef.type = BodyDef.BodyType.StaticBody;
bodyDef.position.set(getX() + getWidth() / 2, getY() + getHeight() / 2);
body = world.createBody(bodyDef);
FixtureDef fixtureDef = new FixtureDef();
PolygonShape shape = new PolygonShape();
shape.setAsBox(getWidth() / 2, getHeight() / 2);
fixtureDef.shape = shape;
fixtureDef.friction = 0;
fixtureDef.density = 700;
fixtureDef.restitution = 1;
body.createFixture(fixtureDef);
}
}

我的球：

public class Ball extends GameObject {
public Ball(World world) {
super(ballTexture, BALL_RADIUS * 2, BALL_RADIUS * 2, new Vector2(WORLD_WIDTH / 2, BALL_Y), world);
}
@Override
protected void defineBody() {
BodyDef bodyDef = new BodyDef();
bodyDef.type = BodyDef.BodyType.DynamicBody;
bodyDef.position.set(getX() + getWidth() / 2, getOriginY() + getHeight() / 2);
System.out.println("X: " + (getX() + getWidth() / 2) + " Y: " + (getY() + getHeight() / 2));
body = world.createBody(bodyDef);
System.out.println(bodyDef.position);
System.out.println(body.getPosition());
FixtureDef fixtureDef = new FixtureDef();
CircleShape shape = new CircleShape();
shape.setRadius(BALL_RADIUS);
fixtureDef.shape = shape;
fixtureDef.friction = 0;
fixtureDef.density = 700;
fixtureDef.restitution = 1;
body.createFixture(fixtureDef);
}
}

蝙蝠工作正常，但鲍尔在创建身体后掉落了 30 个单位：

Before world.createBody() bodyDef.position: X: 200.0 Y: 50.0
After world.createBody() bodyDef.position: (200.0,20.0)
After world.createBody() body.getPosition(): (200.0,20.0)

我的世界万有引力为0。 如果我将球从 50 个单位向上移动到 100 个单位，球同样会下降正好 30 个单位：

Before world.createBody() bodyDef.position: X: 200.0 Y: 100.0
After world.createBody() bodyDef.position: (200.0,70.0)
After world.createBody() body.getPosition(): (200.0,70.0)

Answer 1

bodyDef.position.set(getX() + getWidth() / 2, getOriginY() + getHeight() / 2);

您正在使用 y 原点位置，而不是 y 位置。只需将 getOriginY(( 更改为 getY((。