package test;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class FrameTest extends JFrame implements ActionListener
{
  JButton bt1=new JButton(\"红色\");
  JButton bt=new JButton(\"1234567\");
  JButton bt2=new JButton(\"绿色\"); 
  JPanel pan;
  FrameTest()
  {
    setTitle(\"单击事件\");
    setSize(300,300);
    setBackground(Color.white);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE );
       pan=new JPanel();
    pan.setLayout(new FlowLayout());
    bt1.addActionListener(this);
    bt2.addActionListener(this);
    pan.add(bt);
    pan.add(bt1);
    pan.add(bt2);
    setContentPane(pan);
    setVisible(true);
  }
  public static void main(String args[])
  {
    JFrame frame=new FrameTest();
  }
  public void actionPerformed(ActionEvent e)
  {
    if(e.getSource()==bt1)             //按你这样写
      pan.setBackground(Color.red);     //这里会出现不能认识的对象
      if(e.getSource()==bt2)
        pan.setBackground(Color.cyan);  //这里也是一样.
  }
}