程序9_2.java

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

public class 程序9_2 {
    JFrame frame = new JFrame("JList Demo");
    JList list;
    DefaultListModel listModel;
    JPanel panel; 
    JTextField tf;
    JButton button;
    public static void main(String[] args) {
        程序9_2 ld = new 程序9_2();
        ld.go();
    }

    public void go() {
        listModel = new DefaultListModel();
        listModel.addElement("one");
        listModel.addElement("two");
        listModel.addElement("three");
        listModel.addElement("four");
        list = new JList<>(listModel);
        // 将列表放入滚动窗格JSrollPane中
        JScrollPane jsp = new JScrollPane(list,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        Container cp = frame.getContentPane();
        cp.add(jsp);
        tf =  new JTextField(15);
        button = new JButton("add new item");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                listModel.addElement(tf.getText());  // 添加新的可选项
            }
        }); 
        panel = new JPanel();
        panel.add(tf);
        panel.add(button);
        cp.add(panel,BorderLayout.SOUTH);
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}