JavaFX - 如何控制带滑块的矩形

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Slider;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.scene.shape.StrokeLineCap;
import javafx.stage.Stage;

public class Main extends Application {

  @Override
  public void start(Stage primaryStage) {
    Group root = new Group();
    Scene scene = new Scene(root, 500, 260);

    Rectangle roundRect = new Rectangle(50, 50, 400, 130);

    roundRect.setArcWidth(30);
    roundRect.setArcHeight(60);

    roundRect.setFill(null);
    roundRect.setStroke(Color.DARKORANGE);
    roundRect.setStrokeWidth(2);
    roundRect.setStrokeLineCap(StrokeLineCap.BUTT);

    root.getChildren().add(roundRect);

    Slider slider = new Slider(30, 150, 30);
    slider.setLayoutX(250 - slider.getWidth() / 2);
    slider.setLayoutY(115 - slider.getHeight() / 2);

    slider.widthProperty().addListener((ov, curVal, newVal) -> {
      slider.setLayoutX(250 - slider.getWidth() / 2);
    });

    slider
        .heightProperty()
        .addListener(
            (ov, curVal, newVal) -> slider.setLayoutY(115 - slider.getHeight() / 2));

    roundRect.arcWidthProperty().bind(slider.valueProperty());

    root.getChildren().add(slider);

    Slider slider2 = new Slider(10, 120, 50);
    slider2.setLayoutX(50);
    slider2.setLayoutY(230);

    slider2.widthProperty().addListener((ov, curVal, newVal) -> {
      slider2.setLayoutX(250 - slider2.getWidth() / 2);
    });

    roundRect.yProperty().bind(slider2.valueProperty());
    root.getChildren().add(slider2);

    slider2.valueProperty().addListener(
        (ov, curVal, newVal) -> slider.setLayoutY(slider.getLayoutY()
            + newVal.doubleValue() - curVal.doubleValue()));
    primaryStage.setScene(scene);
    primaryStage.show();
  }

  public static void main(String[] args) {
    launch(args);
  }
}