我在启动我的应用程序时遇到问题，它加载了国家/地区列表，但没有加载其他列表

好像必须专门设置选定的索引才能调用侦听器.

jComboBoxCountries.setModel(...)jComboBoxCountries.setSelectedIndex(0);

并且通过选择一个国家，会向州列表收费，但不会向城市列表收费.

我猜这是同样的问题，一旦您重置状态组合框的模型，您还需要选择其索引.

另一种方法是不选择默认州或城市，而是提示用户选择一个.下面是一些使用这种方法的代码:

import java.awt.*;导入 java.awt.event.*;导入 java.util.*;导入 javax.swing.*;公共类 ComboBoxTwo 扩展 JFrame 实现 ActionListener{私人 JComboBox mainComboBox;私人 JComboBox subComboBox;private Hashtable subItems = new Hashtable();公共 ComboBoxTwo(){String[] items = { "Select Item", "Color", "Shape", "Fruit" };mainComboBox = new JComboBox( items );mainComboBox.addActionListener( this );//防止在使用向上/向下箭头键时触发动作事件//mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);getContentPane().add( mainComboBox, BorderLayout.WEST );//创建具有多个模型的子组合框subComboBox = new JComboBox();subComboBox.setPrototypeDisplayValue("XXXXXXXXXX");//JDK1.4getContentPane().add( subComboBox, BorderLayout.EAST );String[] subItems1 = { "Select Color", "Red", "Blue", "Green" };subItems.put(items[1], subItems1);String[] subItems2 = { "Select Shape", "Circle", "Square", "Triangle" };subItems.put(items[2], subItems2);String[] subItems3 = { "选择水果", "Apple", "Orange", "Banana" };subItems.put(items[3], subItems3);mainComboBox.setSelectedIndex(1);}public void actionPerformed(ActionEvent e){String item = (String)mainComboBox.getSelectedItem();Object o = subItems.get( item );如果(o == 空){subComboBox.setModel( new DefaultComboBoxModel() );}别的{subComboBox.setModel(new DefaultComboBoxModel((String[])o));}}public static void main(String[] args){JFrame frame = new ComboBoxTwo();frame.setDefaultCloseOperation( EXIT_ON_CLOSE );框架.pack();frame.setLocationRelativeTo( null );frame.setVisible(true);}}

I'm working on a desktop (swing) application with Eclipse IDE. I have three comboboxes (countries, states and cities) and I need to update the data automatically when I selecting a new country or province. I searched lot of information, but all the implementations I found are made on Ajax or the beansbinding framework in NetBeans. I tried a solution by ItemEvent, but I have problems starting my application it loads the list of countries but not the other lists. And by selecting a country is charged the list of states but not the list of cities.

My code:

    jComboBoxCountries.addItemListener(new java.awt.event.ItemListener() {
        public void itemStateChanged(java.awt.event.ItemEvent evt) {
            jComboBoxStates.setModel(new javax.swing.DefaultComboBoxModel(
                    statesOf(evt.getItem()).toArray() ));
            }
        });

    jComboBoxStates.addItemListener(new java.awt.event.ItemListener() {
        public void itemStateChanged(java.awt.event.ItemEvent evt) {
                jComboBoxCities.setModel(new javax.swing.DefaultComboBoxModel(
                    citiesOf(evt.getItem()).toArray()) );
            }
    });

    jComboBoxCountries.setModel(new javax.swing.DefaultComboBoxModel(
            countryList.toArray()));

I have problems starting my application it loads the list of countries but not the other lists

It seems like you have to specifically set the selected index to invoke the listener.

jComboBoxCountries.setModel(...)
jComboBoxCountries.setSelectedIndex(0);

And by selecting a country is charged the list of states but not the list of cities.

I would guess this is the same problem, once you reset the model of the states combobox you would need to select its index as well.

Another approach is to not select a default state or city, but instead prompt the user to select one. Here is some code that uses this approach:

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

public class ComboBoxTwo extends JFrame implements ActionListener
{
    private JComboBox mainComboBox;
    private JComboBox subComboBox;
    private Hashtable subItems = new Hashtable();

    public ComboBoxTwo()
    {
        String[] items = { "Select Item", "Color", "Shape", "Fruit" };
        mainComboBox = new JComboBox( items );
        mainComboBox.addActionListener( this );

        //  prevent action events from being fired when the up/down arrow keys are used
//      mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);
        getContentPane().add( mainComboBox, BorderLayout.WEST );

        //  Create sub combo box with multiple models

        subComboBox = new JComboBox();
        subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4
        getContentPane().add( subComboBox, BorderLayout.EAST );

        String[] subItems1 = { "Select Color", "Red", "Blue", "Green" };
        subItems.put(items[1], subItems1);

        String[] subItems2 = { "Select Shape", "Circle", "Square", "Triangle" };
        subItems.put(items[2], subItems2);

        String[] subItems3 = { "Select Fruit", "Apple", "Orange", "Banana" };
        subItems.put(items[3], subItems3);
        mainComboBox.setSelectedIndex(1);
    }

    public void actionPerformed(ActionEvent e)
    {
        String item = (String)mainComboBox.getSelectedItem();
        Object o = subItems.get( item );

        if (o == null)
        {
            subComboBox.setModel( new DefaultComboBoxModel() );
        }
        else
        {
            subComboBox.setModel( new DefaultComboBoxModel( (String[])o ) );
        }
    }

    public static void main(String[] args)
    {
        JFrame frame = new ComboBoxTwo();
        frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
        frame.pack();
        frame.setLocationRelativeTo( null );
        frame.setVisible( true );
     }
}