如何在Java中的JApplet中添加並不重繪圖紙？

如何添加圖紙ii Japplet而不是將其替換爲新的圖紙？我正在使用repaint（），但它所做的只是替換我現有的矩形。什麼是正確的代碼添加另一個矩形，而不是取代它？如何在Java中的JApplet中添加並不重繪圖紙？

說我有這樣的代碼：（此代碼是不是我的）

import java.applet.Applet; 
import java.awt.*; 

public class MoveBox extends Applet 
{ 
    private int x = 20, y = 20; 
    private int width = 10, height = 10; 
    private int inc = 5; 
    private Color myColor = Color.red; 

    private Button up = new Button("Up"); 
    private Button down = new Button("Down"); 
    private Button left = new Button("Left"); 
    private Button right = new Button("Right"); 
    private Button increase = new Button("[+]"); 
    private Button decrease = new Button("[-]"); 

    // init method 
    public void init() 
    { 
     Panel buttons = new Panel(); 
     buttons.setLayout(new FlowLayout()); 
     buttons.add(up); 
     buttons.add(down); 
     buttons.add(left); 
     buttons.add(right); 
     buttons.add(increase); 
     buttons.add(decrease); 

     setLayout(new BorderLayout()); 
     add("South", buttons); 
    } 
    // public methods 
    public boolean action(Event e, Object o) 
    { 
     if (e.target == up) 
     return handleUp(); 
     else if (e.target == down) 
     return handleDown(); 
     else if (e.target == left) 
     return handleLeft(); 
     else if (e.target == right) 
     return handleRight(); 
     else if (e.target == increase) 
     return handleIncrease(); 
     else if (e.target == decrease) 
     return handleDecrease(); 
     else 
     return super.action(e, o); 
    } 
    public void paint(Graphics g) 
    { 
     g.setColor(myColor); 
     g.fillRect(x,y,width,height); 
    } 
    // private methods 
    private boolean handleUp() 
    { 
     y = y - inc; 
     repaint(); 
     return true; 
    } 
    private boolean handleDown() 
    { 
     y = y + inc; 
     repaint(); 
     return true; 
    } 
    private boolean handleRight() 
    { 
     if (x < size().width) 
     x = x + inc; 
     else 
     x = 0; 
     repaint(); 
     return true; 
    } 
    private boolean handleLeft() 
    { 
     if (x > 0) 
     x = x - inc; 
     else 
     x = size().width; 
     repaint(); 
     return true; 
    } 
    private boolean handleIncrease() 
    { 
     width += 5; 
     height += 5; 
     repaint(); 
     return true; 
    } 
    private boolean handleDecrease() 
    { 
     if (width > 5) 
     { 
     width -= 5; 
     height -= 5; 
     } 
     repaint(); 
     return true; 
    } 
}

如何添加另一個矩形當我按下按鈕，上，下，左，右？

來源

2012-12-16 Ma Rk Vilches