How to keep all lines drawn already??

Question

Dear friends:
I have following code, it is runnable one, and each time, I can draw Only ONE line between any TWO buttons, and if I draw another line between another pair of buttons, the First line dispear,
But I hope all line I drwa before will be kept and until I delete or remove them,
How to do it??
package com.lib;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
public class PaintTest
    public PaintTest()
        Parent parent = new Parent();
        TargetSelector selector = new TargetSelector(parent);
        parent.setLayout(new BorderLayout());
        parent.add(getPanel(selector), "West");
        parent.add(getPanel(selector), "East");
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(parent);
        f.setSize(500,400);
        f.setLocation(200,200);
        f.setVisible(true);
    private JPanel getPanel(TargetSelector selector)
        JPanel panel = new JPanel(new GridBagLayout());
        Dimension d = panel.getPreferredSize();
        d.width = 240;
        panel.setPreferredSize(d);
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(5,5,5,5);
        gbc.weighty = 1.0;
        gbc.weightx = 1.0;
        gbc.fill = gbc.BOTH;
        gbc.gridwidth = gbc.REMAINDER;
        for(int j = 0; j < 4; j++)
            JPanel p = new JPanel();
            p.setBackground(new Color(220,240,240));
            p.setBorder(BorderFactory.createEtchedBorder());
            p.addMouseListener(selector);
            panel.add(p, gbc);
        return panel;
    public static void main(String[] args)
        new PaintTest();
class Parent extends JPanel
    Line2D line;
    public Parent()
        line = new Line2D.Double();
    public void paint(Graphics g)  // paint will draw over the child components
        super.paint(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setPaint(Color.red);
        g2.draw(line);
    public void setLine(Point[] points)
        line.setLine(points[0], points[1]);
        repaint();
class TargetSelector extends MouseAdapter
    Parent parent;
    JPanel selectedPanel;
    final int
        NORTH =  2,
        NW    =  3,
        WEST  =  1,
        SW    =  9,
        SOUTH =  8,
        SE    = 12,
        EAST  =  4,
        NE    =  6;
    public TargetSelector(Parent parent)
        this.parent = parent;
    public void mousePressed(MouseEvent e)
        JPanel panel = (JPanel)e.getSource();
        Point p = e.getPoint();
        Point pParent = SwingUtilities.convertPoint(panel, p, parent);
        if(selectedPanel == null)
            selectedPanel = panel;
        else
            parent.setLine(getClosestPoints(selectedPanel, panel));
            selectedPanel = null;
    private Point[] getClosestPoints(Component c1, Component c2)
        Point p1 = getClosestPoint(c1, c2);
        Point p2 = getClosestPoint(c2, c1);
        return new Point[] {p1, p2};
    private Point getClosestPoint(Component c1, Component c2)
        Rectangle r1 = SwingUtilities.convertRectangle(c1.getParent(),
                                                       c1.getBounds(), parent);
        Rectangle r2 = SwingUtilities.convertRectangle(c2.getParent(),
                                                       c2.getBounds(), parent);
        int outcode = r1.outcode(r2.getCenterX(), r2.getCenterY());
        Point p = new Point();
        switch(outcode)
            case NORTH:
                p.x = r1.x + r1.width/2;
                p.y = r1.y;
                break;
            case NW:
                p.x = r1.x;
                p.y = r1.y;
                break;
            case WEST:
                p.x = r1.x;
                p.y = r1.y + r1.height/2;
                break;
            case SW:
                p.x = r1.x;
                p.y = r1.y + r1.height -1;
                break;
            case SOUTH:
                p.x = r1.x + r1.width/2;
                p.y = r1.y + r1.height -1;
                break;
            case SE:
                p.x = r1.x + r1.width -1;
                p.y = r1.y + r1.height -1;
                break;
            case EAST:
                p.x = r1.x + r1.width -1;
                p.y = r1.y + r1.height/2;
                break;
            case NE:
                p.x = r1.x + r1.width -1;
                p.y = r1.y;
                break;
            case 0 /* INSIDE */:
                System.out.println("selectedPanel == panel");
                break;
            default:
                throw new IllegalArgumentException("illegal outcode: " + outcode);
        return p;
}Thanks so much in advance
Sunny

Answer 1

Dear friends:
I have following code, it is runnable one, and each
time, I can draw Only ONE line between any TWO
buttons, and if I draw another line between another
pair of buttons, the First line dispear,
But I hope all line I drwa before will be kept and
until I delete or remove them,
How to do it??As itchyscratchy said, store all the information and paint it each time. Also, read this article:
http://java.sun.com/products/jfc/tsc/articles/painting/index.html