LibGDX: ActorGestureListener after change position

I have this code to get pan touch inside an Image and it works fine, but when I uncomment this line

img.setPosition(100, 100);

it doesn’t work anymore, why?

Texture tex = new Texture(Gdx.files.internal("square.png"));
        final Image img = new Image(tex);
        //img.setPosition(100, 100);
        img.setSize(157,45);
        img.setColor(0,0,0,1f);

        img.addListener( new ActorGestureListener(){

            @Override
            public void pan(InputEvent event, float x, float y, float deltaX, float deltaY) {
                super.pan(event, x, y, deltaX, deltaY);

                int minX = (int)img.getX();
                int maxX = (int)img.getX()+(int)img.getWidth();
                int minY = (int)img.getY();
                int maxY = (int)img.getY()+(int)img.getHeight();

                if ((x>minX && x<maxX)&&(y>minY && y<maxY)){

                    Utils.print("PAN");
                }
            }
        });

        stage.addActor(img);