JavaFX - 如何将节点大小设置为负

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class Main extends Application {
  public static void main(String[] args) {
    Application.launch(args);
  }

  @Override
  public void start(Stage stage) {
    Button btn = new Button("Hello JavaFX!");

    HBox root = new HBox();
    root.getChildren().addAll(btn);

    Scene scene = new Scene(root);
    stage.setScene(scene);
    stage.setTitle("Sizes of a Node");
    stage.show();

    btn.setWrapText(true);
    btn.setPrefWidth(80);
    stage.sizeToScene();

    System.out.println("btn.getContentBias() = " + btn.getContentBias());

    System.out.println("btn.getPrefWidth() = " + btn.getPrefWidth()
        + ", btn.getPrefHeight() = " + btn.getPrefHeight());

    System.out.println("btn.getMinWidth() = " + btn.getMinWidth()
        + ", btn.getMinHeight() = " + btn.getMinHeight());

    System.out.println("btn.getMaxWidth() = " + btn.getMaxWidth()
        + ", btn.getMaxHeight() = " + btn.getMaxHeight());

    double prefWidth = btn.prefWidth(-1);
    System.out.println("btn.prefWidth(-1) = " + prefWidth
        + ", btn.prefHeight(prefWidth) = " + btn.prefHeight(prefWidth));

    double minWidth = btn.minWidth(-1);
    System.out.println("btn.minWidth(-1) = " + minWidth
        + ", btn.minHeight(minWidth) = " + btn.minHeight(minWidth));

    double maxWidth = btn.maxWidth(-1);
    System.out.println("btn.maxWidth(-1) = " + maxWidth
        + ", btn.maxHeight(maxWidth) = " + btn.maxHeight(maxWidth));

    System.out.println("btn.getWidth() = " + btn.getWidth()
        + ", btn.getHeight() = " + btn.getHeight());
  }
}