从ComboBox中选择后立即更新颜色变量

Question

赋值要求超类Shape和两个子类Circle和Square。

我要创建一个小程序，用于从三个独立的JComboBox中选择形状（圆形或方形），大小和颜色。

每次用户点击画布时，应根据组合框中的选择创建Shape类的对象，并将其存储在要打印的ArrayList中。

更新颜色变量时会出现某种“滞后”现象。每次我从与更新颜色相关联的ComboBox中进行选择并返回单击画布时，将使用先前选择的颜色打印形状，然后打印的下一个形状是相应更新的颜色。

以下是代码：

    public class WholePanel extends JPanel
{
   private Color currentColor;
   private int size = 10;
   private Shape shape;
   private String SHAPE = "Circle";
   private String SIZE, CURRENTCOLOR;
   private CanvasPanel canvas;
   private JPanel topPanel, topSplitPanel;
   private JButton undo;
   private ArrayList <Shape>shapeList;
   private JComboBox shapeCombo, sizeCombo, colorCombo;

   public WholePanel()
   {
      //default color to draw is black 

      shapeList = new ArrayList();

      // label for displaying what to input
      Label label1 = new Label("Choose Circle or Square, its size, and its color.");

  // new button to undo last task
  undo = new JButton ("Undo");

  // combo box for selecting shape
  String[] circleSquare = {"Circle", "Square"};
  shapeCombo = new JComboBox(circleSquare);


  //combo box for selecting size
  String[] sizezzz = {"10","20","30","40","50"};
  sizeCombo = new JComboBox(sizezzz);


  //combo box for selecting color
  String[] colores = {"black","red","blue","green","orange"};
  colorCombo = new JComboBox(colores);


  // panel for displaying the three combo boxes and the undo button
  topPanel = new JPanel(new FlowLayout());
  topPanel.add(shapeCombo);
  topPanel.add(sizeCombo);
  topPanel.add(colorCombo);
  topPanel.add(undo);

  // new panel with grid layout for displaying label above panel including combo boxes
  topSplitPanel = new JPanel(new GridLayout(2,1));
  topSplitPanel.add(label1);
  topSplitPanel.add(topPanel);

  // creates new object of CanvasPanel
  canvas = new CanvasPanel();

  // add ActionListeners to the undo button and each of JComboBox
  undo.addActionListener (new ButtonListener());
  shapeCombo.addActionListener (new ComboListener());
  sizeCombo.addActionListener (new ComboListener());
  colorCombo.addActionListener (new ComboListener());

  //adds mouse listener to the canvas
  MouseListener pointListener = new PointListener();
  canvas.addMouseListener(pointListener);


 JSplitPane sp = new JSplitPane(JSplitPane.VERTICAL_SPLIT, topSplitPanel, canvas);
 setLayout(new BorderLayout());
  add(sp);
}

  //CanvasPanel is the panel where shapes will be drawn
  private class CanvasPanel extends JPanel
   {

  //this method draws all shapes 
  public void paintComponent(Graphics page)
   {
        super.paintComponent(page);
        setBackground(Color.WHITE);

       /*for(int i=0; i<shapeList.size(); i++)
        {
            shape = shapeList.get(i);
            shape.draw(page);
        }*/
       for (Shape shapee : shapeList)
        {
            shapee.draw(page);
        }


   }     
} //end of CanvasPanel class


   //ButtonListener defined actions to take in case

     //"Undo" is chosen.
   private class ButtonListener implements ActionListener
{
  public void actionPerformed (ActionEvent event)
  {
      shapeList.remove(shapeList.size()-1);
  }
} // end of ButtonListener


   // listener class to set the color chosen by a user using
   // color combo box, set the size chosen using size combo box
   // or set the shape (circle or square) using shape combo box
   private class ComboListener implements ActionListener
{
    public void actionPerformed(ActionEvent event)
     {
      if(event.getSource()==shapeCombo)
      {
          SHAPE = (String) shapeCombo.getSelectedItem();
      }
      if(event.getSource()==sizeCombo)
      {
          SIZE = (String) sizeCombo.getSelectedItem();
          if (SIZE.equals("10")){ size =10;}
          if (SIZE.equals("20")){ size =20;}
          if (SIZE.equals("30")){ size =30;}
          if (SIZE.equals("40")){ size =40;}
          if (SIZE.equals("50")){ size =50;}
      }
      if(event.getSource()==colorCombo)
      {
          CURRENTCOLOR = (String) colorCombo.getSelectedItem();
          if(CURRENTCOLOR.equals("black")){currentColor = Color.black;}
          if(CURRENTCOLOR.equals("red")){currentColor = Color.red;}
          if(CURRENTCOLOR.equals("blue")){currentColor = Color.blue;}
          if(CURRENTCOLOR.equals("green")){currentColor = Color.green;}
          if(CURRENTCOLOR.equals("orange")){currentColor = Color.orange;}
      }

     }
} // end of ComboListener


   // listener class that listens to the mouse
   public class PointListener implements MouseListener
{
 //in case that a user presses using a mouse,
 //record the point where it was pressed.
 public void mousePressed (MouseEvent event)
  {
     int X = event.getX();
     int Y = event.getY();

     if (SHAPE.equals("Square"))
     {
         shapeList.add(new Square(X-(size/2),Y-(size/2),size,currentColor));
     }

     if (SHAPE.equals("Circle"))
     {
         shapeList.add(new Circle(X-(size/2),Y-(size/2),size,currentColor));
     }
  }
 public void mouseReleased (MouseEvent event) {}
 public void mouseClicked (MouseEvent event) {}
 public void mouseEntered (MouseEvent event) {}
 public void mouseExited (MouseEvent event) {}

} // end of PointListener

} // end of Whole Panel Class