如何在vbox中正确堆叠形状？JavaFX

我目前正在尝试用javafx创建河内塔。我对如何使矩形正确地堆叠在每个VBox中有点茫然。如果运行下面的代码，将多个块移动到同一个vbox将导致添加的最新块位于底部，但它应该位于顶部。我怎样才能正确地实现这一点

提前谢谢

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.Background;
import javafx.scene.layout.BackgroundFill;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.CornerRadii;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.paint.Paint;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class TowersOfHanoi extends Application {
Rectangle selectedpiece;
VBox selectedbox;
Paint temp;

public static void main(String[] args){
    launch();
}
@Override
public void start(Stage mainStage) throws Exception {
    GridPane gp = new GridPane();

    //Adding 3 panels
    VBox panel1 = new VBox();
    panel1.setBackground(new Background(new BackgroundFill(Color.LIGHTGREEN, CornerRadii.EMPTY, Insets.EMPTY)));
    panel1.setAlignment(Pos.BOTTOM_CENTER);
    panel1.setPrefHeight(980);
    panel1.setPrefWidth(500);
    panel1.setSpacing(1);
    panel1.setPadding(new Insets(0, 20, 10, 20));
    panel1.setOnMouseClicked(new panelEventHandler());

    VBox panel2 = new VBox();
    panel2.setBackground(new Background(new BackgroundFill(Color.LIGHTBLUE, CornerRadii.EMPTY, Insets.EMPTY)));
    panel2.setAlignment(Pos.BOTTOM_CENTER);
    panel2.setPrefHeight(500);
    panel2.setPrefWidth(500);
    panel2.setSpacing(1);
    panel2.setPadding(new Insets(0, 20, 10, 20));
    panel2.setOnMouseClicked(new panelEventHandler());

    VBox panel3 = new VBox();
    panel3.setBackground(new Background(new BackgroundFill(Color.LIGHTSALMON, CornerRadii.EMPTY, Insets.EMPTY)));
    panel3.setAlignment(Pos.BOTTOM_CENTER);
    panel3.setPrefHeight(500);
    panel3.setPrefWidth(500);
    panel3.setSpacing(1);
    panel3.setPadding(new Insets(0, 20, 10, 20));
    panel3.setOnMouseClicked(new panelEventHandler());

    //Adding all 4 pieces
    Rectangle piece1 = new Rectangle(250, 50);
    piece1.setFill(Color.RED);
    piece1.setStroke(Color.BLACK);
    panel1.getChildren().add(piece1);
    piece1.setOnMouseClicked(new pieceEventHandler());

    Rectangle piece2 = new Rectangle(300, 50);
    piece2.setFill(Color.BLUE);
    piece2.setStroke(Color.BLACK);
    panel1.getChildren().add(piece2);
    piece2.setOnMouseClicked(new pieceEventHandler());

    Rectangle piece3 = new Rectangle(350, 50);
    piece3.setFill(Color.CORAL);
    piece3.setStroke(Color.BLACK);
    panel1.getChildren().add(piece3);
    piece3.setOnMouseClicked(new pieceEventHandler());

    Rectangle piece4 = new Rectangle(400, 50);
    piece4.setFill(Color.MAGENTA);
    piece4.setStroke(Color.BLACK);
    panel1.getChildren().add(piece4);
    piece4.setOnMouseClicked(new pieceEventHandler());

    gp.getChildren().add(panel1);
    gp.getColumnConstraints().add(new ColumnConstraints(500));
    GridPane.setColumnIndex(panel1, 0); 
    gp.getChildren().add(panel2);
    GridPane.setColumnIndex(panel2, 5);
    gp.getChildren().add(panel3);
    GridPane.setColumnIndex(panel3, 10);


    Scene scene = new Scene(gp, 1500, 980);
    mainStage.setScene(scene);
    mainStage.show();
}



class panelEventHandler implements EventHandler<MouseEvent>{

    @Override
    public void handle(MouseEvent event) {

        if(selectedpiece == null){
            ;
        }
        else{
            selectedbox = (VBox)event.getSource();
            if(selectedbox.getChildren().contains(selectedpiece)){
                ;
            }
            else{
                VBox parentbox = (VBox) selectedpiece.getParent();
                parentbox.getChildren().remove(selectedpiece);
                selectedbox.getChildren().add(selectedpiece);
                selectedpiece.setFill(temp);
                selectedpiece = null;
                selectedbox = null;

            }
        }
    }

}

class pieceEventHandler implements EventHandler<MouseEvent>{

    @Override
    public void handle(MouseEvent event) {
        if(selectedpiece == null){
        selectedpiece = (Rectangle) event.getSource();
        temp = selectedpiece.getFill();
        selectedpiece.setFill(Color.YELLOW);
        }
        else if(selectedpiece == (Rectangle) event.getSource()){
            selectedpiece.setFill(temp);
            selectedpiece = null;
        }
        else{
            selectedpiece.setFill(temp);
            selectedpiece = (Rectangle) event.getSource();
            temp = selectedpiece.getFill();
            selectedpiece.setFill(Color.YELLOW);
        }
    }

}

}

只需更换

selectedbox.getChildren().add(selectedpiece);

与

---

哈，我真不敢相信事情会这么简单。多谢各位@krambo ObservableList只是一个带有附加功能的常规java.util.List，因此您可以使用任何常用的List方法。

selectedbox.getChildren().add(0, selectedpiece);