下拉列表

package ComboBoxDemo;

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

import java.util.*;

public class ComboBoxDemo extends JFrame {

private String[] cities = {"北京","上海","南京","苏州","珠海","广州"};

private JTextField textField = new JTextField(15);

private JComboBox comboBox = new JComboBox();

private JButton button = new JButton("添加更多城市选项");

private int count = 0;

public ComboBoxDemo(String title) {

super(title);

for(int i = 0; i < 4; i++)

comboBox.addItem(cities[count++]);

button.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

if(count < cities.length)

comboBox.addItem(cities[count++]);

}

});

comboBox.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

textField.setText("index: " + comboBox.getSelectedIndex() + " " + comboBox.getSelectedItem());

}

});

comboBox.setEditable(true);

textField.setEditable(false);

Container contentPane = getContentPane();

contentPane.setLayout(new FlowLayout());

contentPane.add(comboBox);

contentPane.add(button);

contentPane.add(textField);

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

pack();

setVisible(true);

}

public static void main(String[] args) {

// TODO Auto-generated method stub

new ComboBoxDemo("Hello");

}

}