Map集合可以保存键值映射关系，这非常适合本实例所需要的数据结构，所有省份信息可以保存为Map集合的键，而每个键可以保存对应的城市信息，本实例就是利用Map集合实现了省市级联选择框，当选择省份信息时，将改变城市下拉选择框对应的内容。
思路分析：
1. 创建全国（省，直辖市，自治区）映射集合，即LinkedHashMap对象，使用Map接口的put()方法向集合中添加指定的省与城市的映射关系，其中值为String型一维数组。
代码如下：
CityMap.java
import java.util.LinkedHashMap;
import java.util.Map;
public class CityMap {
/**
* 全国（省，直辖市，自治区）映射集合
*/
public static Map model=new LinkedHashMap();
static{
model.put("北京", new String[]{"北京"});
model.put("上海", new String[]{"上海"});
model.put("天津", new String[]{"天津"});
model.put("重庆", new String[]{"重庆"});
model.put("黑龙江", new String[]{"哈尔滨","齐齐哈尔","牡丹江","大庆","伊春","双鸭山","鹤岗","鸡西","佳木斯","七台河","黑河","绥化","大兴安岭"});
model.put("吉林", new String[]{"长春","延边","吉林","白山","白城","四平","松原","辽源","大安","通化"});
model.put("辽宁", new String[]{"沈阳","大连","葫芦岛","旅顺","本溪","抚顺","铁岭","辽阳","营口","阜新","朝阳","锦州","丹东","鞍山"});
model.put("内蒙古", new String[]{"呼和浩特","呼伦贝尔","锡林浩特","包头","赤峰","海拉尔","乌海","鄂尔多斯","通辽"});
model.put("河北", new String[]{"石家庄","唐山","张家口","廊坊","邢台","邯郸","沧州","衡水","承德","保定","秦皇岛"});
model.put("河南", new String[]{"郑州","开封","洛阳","平顶山","焦作","鹤壁","新乡","安阳","濮阳","许昌","漯河","三门峡","南阳","商丘","信阳","周口","驻马店"});
model.put("山东", new String[]{"济南","青岛","淄博","威海","曲阜","临沂","烟台","枣庄","聊城","济宁","菏泽","泰安","日照","东营","德州","滨州","莱芜","潍坊"});
model.put("山西", new String[]{"太原","阳泉","晋城","晋中","临汾","运城","长治","朔州","忻州","大同","吕梁"});
model.put("江苏", new String[]{"南京","苏州","昆山","南通","太仓","吴县","徐州","宜兴","镇江","淮安","常熟","盐城","泰州","无锡","连云港","扬州","常州","宿迁"});
model.put("安徽", new String[]{"合肥","巢湖","蚌埠","安庆","六安","滁州","马鞍山","阜阳","宣城","铜陵","淮北","芜湖","毫州","宿州","淮南","池州"});
model.put("陕西", new String[]{"西安","韩城","安康","汉中","宝鸡","咸阳","榆林","渭南","商洛","铜川","延安"});
model.put("宁夏", new String[]{"银川","固原","中卫","石嘴山","吴忠"});
model.put("甘肃", new String[]{"兰州","白银","庆阳","酒泉","天水","武威","张掖","甘南","临夏","平凉","定西","金昌"});
model.put("青海", new String[]{"西宁","海北","海西","黄南","果洛","玉树","海东","海南"});
model.put("湖北", new String[]{"武汉","宜昌","黄冈","恩施","荆州","神农架","十堰","咸宁","襄樊","孝感","随州","黄石","荆门","鄂州"});
model.put("湖南", new String[]{"长沙","邵阳","常德","郴州","吉首","株洲","娄底","湘潭","益阳","永州","岳阳","衡阳","怀化","韶山","张家界"});
model.put("浙江", new String[]{"杭州","湖州","金华","宁波","丽水","绍兴","雁荡山","衢州","嘉兴","台州","舟山","温州"});
model.put("江西", new String[]{"南昌","萍乡","九江","上饶","抚州","吉安","鹰潭","宜春","新余","景德镇","赣州"});
model.put("福建", new String[]{"福州","厦门","龙岩","南平","宁德","莆田","泉州","三明","漳州"});
model.put("贵州", new String[]{"贵阳","安顺","赤水","遵义","铜仁","六盘水","毕节","凯里","都匀"});
model.put("四川", new String[]{"成都","泸州","内江","凉山","阿坝","巴中","广元","乐山","绵阳","德阳","攀枝花","雅安","宜宾","自贡","甘孜州","达州","资阳","广安","遂宁","眉山","南充"});
model.put("广东", new String[]{"广州","深圳","潮州","韶关","湛江","惠州","清远","东莞","江门","茂名","肇庆","汕尾","河源","揭阳","梅州","中山","德庆","阳江","云浮","珠海","汕头","佛山"});
model.put("广西", new String[]{"南宁","桂林","阳朔","柳州","梧州","玉林","桂平","贺州","钦州","贵港","防城港","百色","北海","河池","来宾","崇左"});
model.put("云南", new String[]{"昆明","保山","楚雄","德宏","红河","临沧","怒江","曲靖","思茅","文山","玉溪","昭通","丽江","大理"});
model.put("海南", new String[]{"海口","三亚","儋州","琼山","通什","文昌"});
model.put("新疆", new String[]{"乌鲁木齐","阿勒泰","阿克苏","昌吉","哈密","和田","喀什","克拉玛依","石河子","塔城","库尔勒","吐鲁番","伊宁"});
}
}
2. 定义获取省份的方法，创建一个Map集合，将上一步得到的映射集合赋值给它，使用Map集合的keySet()方法获取该集合中的所有键对象组成的Set集合，即为省分集合，创建一个Object型一维数组，使用Set接口的toArray()方法将Set集合转换为数组，返回此数组作为省份选择下拉列表的参数。
3. 使用JComboBox类的setModel()方法为省份下拉列表添加省份信息，参数即为上一步中的获取省份方法。
4. 定义根据省份获取市/县的方法，创建一个Map集合，将步骤1中得到的映射集合赋值给它，使用Map集合的get()方法获取指定键的值，即为市/县集合，创建一个String[]型一维数组，将市/县集合赋值给该数组。
5. 定义省份下拉列表的选项状态更改事件，在该事件中通过JComboBox类的getSelectedItem()方法获取选中的省份，默认为省份集合中的第一个值，然后使用JComboBox类的removeAllItems()方法清空市/县列表，根据选中的省份获取市/县数组，最后使用JComboBox的setModel()方法重新添加市/县列表的值。
代码如下：
BackgroundPanel.java
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.JPanel;
/**
* 带背景的面板组件
*
* @author ZhongWei Lee
*/
public class BackgroundPanel extends JPanel {
/**
*
*/
private static final long serialVersionUID = 7758689434195492602L;
/**
* 背景图片
*/
private Image image;
/**
* 构造方法
*/
public BackgroundPanel() {
super();
setOpaque(false);
setLayout(null);
}
/**
* 设置图片的方法
*/
public void setImage(Image image) {
this.image = image;
}
@Override
protected void paintComponent(Graphics g) {// 重写绘制组件外观
if (image != null) {
int width = getWidth();// 获取组件大小
int height = getHeight();
g.drawImage(image, 0, 0, width, height, this);// 绘制图片与组件大小相同
}
super.paintComponent(g);// 执行超类方法
}
}
SwingResourceManager.java
import java.awt.Image;
import java.awt.Toolkit;
import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Iterator;
import javax.swing.ImageIcon;
/**
* Utility class for managing resources such as colors, fonts, images, etc.
*
* This class may be freely distributed as part of any application or plugin.
*
* Copyright (c) 2003 - 2004, Instantiations, Inc.
All Rights Reserved
*
* @author scheglov_ke
*/
public class SwingResourceManager {
/**
* Maps image names to images
*/
private static HashMap m_ClassImageMap = new HashMap();
/**
* Returns an image encoded by the specified input stream
* @param is InputStream The input stream encoding the image data
* @return Image The image encoded by the specified input stream
*/
private static Image getImage(InputStream is) {
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte buf[] = new byte[1024 * 4];
while (true) {
int n = is.read(buf);
if (n == -1)
break;
baos.write(buf, 0, n);
}
baos.close();
return Toolkit.getDefaultToolkit().createImage(baos.toByteArray());
} catch (Throwable e) {
return null;
}
}
/**
* Returns an image stored in the file at the specified path relative to the specified class
* @param clazz Class The class relative to which to find the image
* @param path String The path to the image file
* @return Image The image stored in the file at the specified path
*/
public static Image getImage(Class clazz, String path) {
String key = clazz.getName() + '|' + path;
Image image = m_ClassImageMap.get(key);
if (image == null) {
if ((path.length() > 0) && (path.charAt(0) == '/')) {
String newPath = path.substring(1, path.length());
image = getImage(new BufferedInputStream(clazz.getClassLoader().getResourceAsStream(newPath)));
} else {
image = getImage(clazz.getResourceAsStream(path));
}
m_ClassImageMap.put(key, image);
}
return image;
}
/**
* Returns an image stored in the file at the specified path
* @param path String The path to the image file
* @return Image The image stored in the file at the specified path
*/
public static Image getImage(String path) {
return getImage("default", path); //$NON-NLS-1$
}
/**
* Returns an image stored in the file at the specified path
* @param section String The storage section in the cache
* @param path String The path to the image file
* @return Image The image stored in the file at the specified path
*/
public static Image getImage(String section, String path) {
String key = section + '|' + SwingResourceManager.class.getName() + '|' + path;
Image image = m_ClassImageMap.get(key);
if (image == null) {
try {
FileInputStream fis = new FileInputStream(path);
image = getImage(fis);
m_ClassImageMap.put(key, image);
fis.close();
} catch (IOException e) {
return null;
}
}
return image;
}
/**
* Clear cached images in specified section
* @param section the section do clear
*/
public static void clearImages(String section) {
for (Iterator I = m_ClassImageMap.keySet().iterator(); I.hasNext();) {
String key = I.next();
if (!key.startsWith(section + '|'))
continue;
Image image = m_ClassImageMap.get(key);
image.flush();
I.remove();
}
}
/**
* Returns an icon stored in the file at the specified path relative to the specified class
* @param clazz Class The class relative to which to find the icon
* @param path String The path to the icon file
* @return Icon The icon stored in the file at the specified path
*/
public static ImageIcon getIcon(Class clazz, String path) {
return getIcon(getImage(clazz, path));
}
/**
* Returns an icon stored in the file at the specified path
* @param path String The path to the icon file
* @return Icon The icon stored in the file at the specified path
*/
public static ImageIcon getIcon(String path) {
return getIcon("default", path); //$NON-NLS-1$
}
/**
* Returns an icon stored in the file at the specified path
* @param section String The storage section in the cache
* @param path String The path to the icon file
* @return Icon The icon stored in the file at the specified path
*/
public static ImageIcon getIcon(String section, String path) {
return getIcon(getImage(section, path));
}
/**
* Returns an icon based on the specified image
* @param image Image The original image
* @return Icon The icon based on the image
*/
public static ImageIcon getIcon(Image image) {
if (image == null)
return null;
return new ImageIcon(image);
}
}
MainFrame.java
import java.awt.EventQueue;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.util.Map;
import java.util.Set;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingConstants;
import javax.swing.UIManager;
import javax.swing.border.TitledBorder;
public class MainFrame extends JFrame {
/**
*
*/
private static final long serialVersionUID = -4595347311922711984L;
private JTextField textField_3;
private JTextField textField_1;
private JComboBox comboBox_1;
private JTextField textField;
private JComboBox cityComboBox;
private JComboBox comboBox;
/**
* Launch the application
*
* @param args
*/
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
MainFrame frame = new MainFrame();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame
*/
public MainFrame() {
getContentPane().setLayout(null);
setBounds(100, 100, 518, 379);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//获取默认的市/县
String province=(String)getProvince()[0];
setTitle("输入指定省/直辖市查询对应的市县");
final BackgroundPanel backgroundPanel = new BackgroundPanel();
backgroundPanel.setImage(SwingResourceManager.getImage(MainFrame.class, "/images/background.jpg"));
backgroundPanel.setBounds(0, 0, 510, 380);
getContentPane().add(backgroundPanel);
final JPanel panel = new JPanel();
panel.setOpaque(false);
panel.setBounds(36, 126, 438, 70);
backgroundPanel.add(panel);
panel.setLayout(null);
panel.setBorder(new TitledBorder(null, "居住地", TitledBorder.DEFAULT_JUSTIFICATION, TitledBorder.DEFAULT_POSITION, null, null));
cityComboBox = new JComboBox();
cityComboBox.setBounds(245, 25, 124, 27);
panel.add(cityComboBox);
cityComboBox.setModel(new DefaultComboBoxModel(getCity(province)));
comboBox = new JComboBox();
comboBox.setBounds(25, 25, 124, 27);
panel.add(comboBox);
comboBox.addItemListener(new ItemListener() {
public void itemStateChanged(final ItemEvent e) { // 选项状态更改事件
itemChange();
}
});
comboBox.setModel(new DefaultComboBoxModel(getProvince())); // 添加省份信息
final JLabel label = new JLabel();
label.setText("省/直辖市");
label.setBounds(155, 30, 66, 18);
panel.add(label);
final JLabel label_1 = new JLabel();
label_1.setText("市/县");
label_1.setBounds(375, 30, 37, 18);
panel.add(label_1);
final JLabel label_2 = new JLabel();
label_2.setBounds(36, 43, 65, 18);
backgroundPanel.add(label_2);
label_2.setHorizontalAlignment(SwingConstants.RIGHT);
label_2.setHorizontalTextPosition(SwingConstants.LEADING);
label_2.setText("姓 名：");
textField = new JTextField();
textField.setBounds(113, 38, 154, 28);
backgroundPanel.add(textField);
final JLabel label_3 = new JLabel();
label_3.setBounds(36, 84, 65, 18);
backgroundPanel.add(label_3);
label_3.setHorizontalAlignment(SwingConstants.RIGHT);
label_3.setHorizontalTextPosition(SwingConstants.LEADING);
label_3.setText("性 别：");
comboBox_1 = new JComboBox();
comboBox_1.setBounds(113, 81, 66, 25);
backgroundPanel.add(comboBox_1);
comboBox_1.setModel(new DefaultComboBoxModel(new String[] {"男", "女"}));
final JLabel label_4 = new JLabel();
label_4.setBounds(36, 212, 65, 18);
backgroundPanel.add(label_4);
label_4.setHorizontalAlignment(SwingConstants.RIGHT);
label_4.setHorizontalTextPosition(SwingConstants.LEADING);
label_4.setText("详细地址：");
textField_1 = new JTextField();
textField_1.setBounds(113, 208, 367, 28);
backgroundPanel.add(textField_1);
final JLabel label_4_1 = new JLabel();
label_4_1.setBounds(36, 252, 65, 18);
backgroundPanel.add(label_4_1);
label_4_1.setHorizontalTextPosition(SwingConstants.LEADING);
label_4_1.setHorizontalAlignment(SwingConstants.RIGHT);
label_4_1.setText("E-mail：");
textField_3 = new JTextField();
textField_3.setBounds(113, 248, 367, 27);
backgroundPanel.add(textField_3);
final JButton button = new JButton();
button.setBounds(159, 289, 75, 28);
backgroundPanel.add(button);
button.setText("保存");
final JButton button_1 = new JButton();
button_1.setBounds(265, 289, 75, 28);
backgroundPanel.add(button_1);
button_1.setText("重置");
//
}
/**
* 获取省、直辖市，自治区
*
* @return
*/
public Object[] getProvince() {
Map map = CityMap.model;// 获取省份信息保存到Map中
Set set = map.keySet(); // 获取Map集合中的键，并以Set集合返回
Object[] province = set.toArray(); // 转换为数组
return province; // 返回获取的省份信息
}
/**
* 获取指定省对应的市/县
*
* @param selectProvince
* @return
*/
public String[] getCity(String selectProvince) {
Map map = CityMap.model; // 获取省份信息保存到Map中
String[] arrCity = map.get(selectProvince); // 获取指定键的值
return arrCity; // 返回获取的市/县
}
private void itemChange() {
String selectProvince = (String) comboBox.getSelectedItem();
cityComboBox.removeAllItems(); // 清空市/县列表
String[] arrCity = getCity(selectProvince); // 获取市/县
cityComboBox.setModel(new DefaultComboBoxModel(arrCity)); // 重新添加市/县列表的值
}
}
效果如图：