import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;

public class AddButton extends JFrame implements ActionListener{

    private JPanel jp;
    private ArrayList<String> lst=null;
    private JButton addBtn;
    
    public AddButton(){
        lst=new ArrayList<String>();
        lst.add("按钮1");
        lst.add("按钮2");
        jp=new JPanel(new GridLayout(lst.size(),1));
        for(int i=0;i<lst.size();i++){
            JButton jb=new JButton(lst.get(i));
            jp.add(jb);
        }
        addBtn=new JButton("添加一个按钮");
        addBtn.setActionCommand("add");
        addBtn.addActionListener(this);
        this.add(jp);
        this.add(addBtn,BorderLayout.SOUTH);
        this.setSize(400, 300);
        this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
        this.setVisible(true);
    }
    
    /**
    * @param args
    */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        AddButton ab=new AddButton();
    }
    
    @Override
    public void actionPerformed(ActionEvent arg0) {
        // TODO Auto-generated method stub
        if(arg0.getActionCommand().equals("add")){
            System.out.println("add");
            lst.add("按钮3");
            //JButton jb=new JButton(lst.get(2));
            //如何添加到jp中去？？
            //jp.add(jb);
            jp.removeAll();
            jp.setLayout(new GridLayout(lst.size(), 1));
            for (int i = 0; i < lst.size(); i++)
            {
                jp.add(new JButton(lst.get(i)));
            }
            this.repaint();
            jp.validate();
              //期望的效果是网格布局的jp能变成new JPanel(new GridLayout(3,1))的效果
        }
    }

}