LibGDX drag listener on small Actor

Question

I have an Actor which has set a drag listener:

ballActor.addListener(new DragListener() {
    public void drag(InputEvent event, float x, float y, int pointer) {
        ballActor.moveBy(x - ballActor.getWidth() / 2, y - ballActor.getHeight() / 2);
    }
});

This actor is added to a stage:

W = Gdx.graphics.getWidth();
H = Gdx.graphics.getHeight();
camera = new OrthographicCamera(W / RATE, H / RATE);
stage = new Stage(new ScreenViewport(camera));
stage.addActor(ballActor);
Gdx.input.setInputProcessor(stage);

Now if I use meter to pixel ratio 1:1 the drag works very well but if i use another ratio, like 1:160 the drag event is not firing.

In resize method I update the camera:

camera.viewportHeight = H/RATE;
camera.viewportWidth = W/RATE;
camera.position.set(camera.viewportWidth / 2, camera.viewportHeight / 2, 0);
camera.update();

I read that if I use a stage I dont have to translate from screen coordinates to camera coordinates. The actor has set the position, width, height and also bounds. What am I doing wrong?

UPDATE:

Here is the code:

public class Pendulum extends ApplicationAdapter {

    private Stage stage;

    public static final float RATE = 160f; //with 1f..20f drag works

    float W;
    float H;

    @Override
    public void create() {

        W = Gdx.graphics.getWidth() / RATE;
        H = Gdx.graphics.getHeight() / RATE;

        Texture ballTexture = new Texture(Gdx.files.internal("ball.png"), true);
        ballTexture.setFilter(Texture.TextureFilter.MipMapLinearNearest, Texture.TextureFilter.Linear);
        TextureRegion ballRegion = new TextureRegion(ballTexture);

        final Image image = new Image(ballRegion);
        image.setSize(image.getWidth()/RATE, image.getHeight()/RATE);
        image.setPosition(0f, 0f);
        image.addListener(new DragListener() {
            public void drag(InputEvent event, float x, float y, int pointer) {
                Gdx.app.log("LOG", "DRAG IMAGE");
                image.moveBy(x - image.getWidth() / 2, y - image.getHeight() / 2);
            }
        });
        image.debug();
        image.setBounds(image.getX(), image.getY(), image.getWidth(), image.getHeight());

        stage = new Stage(new FitViewport(W, H));
        stage.addActor(image);

        Gdx.input.setInputProcessor(stage);
    }


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

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

        float delta = Math.min(Gdx.graphics.getDeltaTime(), 1 / 30f);
        stage.act(delta);
        stage.draw();
    }

    @Override
    public void dispose() {
        stage.dispose();
    }
}

I need to have RATE bigger than 100f because Image actor has a Box2D Body attached. See here why.

Tenfour04 Tenfour04 · Accepted Answer · 2016-06-06T12:51:57

When using scene2d, you have to use a Viewport, and a Viewport manages the size of its camera. When you set explicit sizes on the camera, Stage will be confused because it assumes the Viewport is managing the camera (there is a now a mismatch between the world coordinates of the camera and the screen size of the viewport).

I'm not sure how you calculated RATE, but what you should probably be doing is using an ExtendViewport or FitViewport. And in your resize() method, instead of modifying the camera, you need to call update() on your viewport.

LibGDX drag listener on small Actor

2 Answers