public class BoardView extends GridPane {

    private final BoardPresenter presenter;
    private final SelectorView selector;

    public BoardView() {
        presenter = new BoardPresenter(this);
        displayBoard(presenter.getBoard());
        selector = new SelectorView(new SelectorPresenter());
        presenter.selectionProperty().addListener((_, _, newValue) -> {
            getChildren().remove(selector);
            if (newValue == null)
                return;
            add(selector, newValue.x(), newValue.y());
        });
    }

public class BoardView extends GridPane {

    private final BoardPresenter presenter;
    private final SelectorView selector;

    public BoardView() {
        presenter = new BoardPresenter(this);
        displayBoard(presenter.getBoard());
        selector = new SelectorView(new SelectorPresenter());
        presenter.selectionProperty().addListener((_, _, newValue) -> {
            getChildren().remove(selector);
            if (newValue == null)
                return;
            add(selector, newValue.x(), newValue.y());
        });
    }