用java做画版

主要用到画板类,可以参考一下:
package test;
import java.applet.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.*;

public class Test extends JApplet {
JButton line;
JButton triangle;
JButton rectangle;
JButton circle;
JButton fill;
JPanel pb;
JPanel pd;
drCanvas ca;

public void init( ) {
Container cp=this.getContentPane();
cp.setLayout(new BorderLayout());

pb=new JPanel();
cp.add(pb,BorderLayout.WEST);
pb.setLayout(new GridLayout(10,1));
pd=new JPanel();
cp.add(pd,BorderLayout.SOUTH);
pd.setLayout(new FlowLayout());
ca=new drCanvas();
cp.add(ca, BorderLayout.CENTER);
line=new JButton("直线");
line.addActionListener(ca);
pb.add(line);
triangle=new JButton("三角形");
triangl