Question

我想创建一个移动平台，当它的位置等于屏幕宽度时改变它的方向，我这样做：

if(bucket.getPosition().x <= Gdx.graphics.getWidth()/PPM){
        do{
            bucket.setLinearVelocity(dt*PPM,0);
        }while (bucket.getPosition().x <= Gdx.graphics.getWidth()/PPM);

}else{
        do{
            bucket.setLinearVelocity(-dt*PPM,0);
        }while (bucket.getPosition().x != 0);
}

但是当我运行它时，我只看到黑屏;

但是当我写这样的时候：

if(bucket.getPosition().x <= Gdx.graphics.getWidth()/PPM){

     bucket.setLinearVelocity(dt*PPM,0);

}else{

      bucket.setLinearVelocity(-dt*PPM,0);      
}

一切正常，但“桶”不会改变其方向：（（

Answer 1

您可以在身体上使用setTransform(vector2,angle)来满足您的要求，并左右移动您的水桶。

我已尝试完成您的要求，请检查。

public class GdxTest extends InputAdapter implements ApplicationListener {

    private SpriteBatch batch;
    private ExtendViewport extendViewport;
    private OrthographicCamera cam;

    private float w=20;
    private float h=22;

    private World world;
    private Box2DDebugRenderer debugRenderer;

    private Array<Body> array;
    private Vector3 vector3;
    private Body bucket;
    Vector2 vector2;
    boolean isLeft;

    @Override
    public void create() {

        vector2=new Vector2();
        isLeft=true;
        cam=new OrthographicCamera();
        extendViewport=new ExtendViewport(w,h,cam);

        batch =new SpriteBatch();
        Gdx.input.setInputProcessor(this);

        world=new World(new Vector2(0,-9.8f),true);
        array=new Array<Body>();
        debugRenderer=new Box2DDebugRenderer();
        vector3=new Vector3();

        BodyDef bodyDef=new BodyDef();
        bodyDef.type= BodyDef.BodyType.KinematicBody;
        bodyDef.position.set(0,0);
        bucket=world.createBody(bodyDef);

        ChainShape chainShape=new ChainShape();
        chainShape.createChain(new float[]{1,5,1,1,5,1,5,5});

        FixtureDef fixtureDef=new FixtureDef();
        fixtureDef.shape=chainShape;
        fixtureDef.restitution=.5f;
        bucket.createFixture(fixtureDef);
        chainShape.dispose();
    }

    @Override
    public void render() {

        Gdx.gl.glClearColor(0,1,1,1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        world.step(1/60f,6,2);
        batch.setProjectionMatrix(cam.combined);
        batch.begin();

        world.getBodies(array);
        for (Body body:array){
            if(body.getUserData()!=null) {
                Sprite sprite = (Sprite) body.getUserData();
                sprite.setPosition(body.getPosition().x-sprite.getWidth()/2, body.getPosition().y-sprite.getHeight()/2);
                sprite.setRotation(body.getAngle()*MathUtils.radDeg);
                sprite.draw(batch);
            }
        }
        batch.end();
        debugRenderer.render(world,cam.combined);


        Vector2 pos=bucket.getTransform().getPosition();
        vector2.set(pos.x+(isLeft?0.05f:-0.05f),pos.y);
        bucket.setTransform(vector2,0);

        if(pos.x>20-5)
            isLeft=false;
        if(pos.x<-1)
            isLeft=true;

    }

    @Override
    public void pause() {

    }

    @Override
    public void resume() {

    }

    @Override
    public void resize(int width, int height) {

        extendViewport.update(width,height);
        cam.position.x = w /2;
        cam.position.y = h/2;
        cam.update();
    }

    private void createPhysicsObject(float x,float y){

        float sizeX=0.5f,sizeY=0.5f;
        BodyDef bodyDef=new BodyDef();
        bodyDef.position.set(x,y);
        bodyDef.type= BodyDef.BodyType.DynamicBody;

        Body body=world.createBody(bodyDef);

        PolygonShape polygonShape=new PolygonShape();
        polygonShape.setAsBox(sizeX,sizeY);
        FixtureDef fixtureDef=new FixtureDef();
        fixtureDef.shape=polygonShape;
        fixtureDef.restitution=.2f;
        fixtureDef.density=2;

        body.createFixture(fixtureDef);
        body.setFixedRotation(false);
        polygonShape.dispose();

        Sprite sprite=new Sprite(new Texture("badlogic.jpg"));
        sprite.setSize(2*sizeX,2*sizeY);
        sprite.setPosition(x-sprite.getWidth()/2,y-sprite.getHeight()/2);
        sprite.setOrigin(sizeX,sizeY);

        body.setUserData(sprite);
    }

    @Override
    public void dispose() {
        batch.dispose();
        debugRenderer.dispose();
        world.dispose();
    }

    @Override
    public boolean touchDown(int screenX, int screenY, int pointer, int button) {

        vector3.set(screenX,screenY,0);
        Vector3 position=cam.unproject(vector3);
        createPhysicsObject(vector3.x,vector3.y);

        return false;
    }
}

循环和黑屏

1 个答案: