java - 使用 Swing 从监听器添加组合框值

Question

我是 Swing 新手。我有一个要求，我需要从数据库获取数据并在组合框中弹出，当组合框监听器执行时，它需要加载值。我不确定我哪里出错了，下面代码中的值没有显示。 如果我错了，有人可以纠正我吗？ 代码:

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

public class ComboBoxSelectionChange extends JFrame
{
    public ComboBoxSelectionChange ()
    {
        initialize();
    }

    private void initialize ()
    {
        setSize(300, 300);
        setLayout(new FlowLayout(FlowLayout.LEFT));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        final JComboBox comboBox = new JComboBox();
        comboBox.setEditable(true);
        final JTextArea textArea = new JTextArea(5, 15);
        textArea.setBorder(new BevelBorder(BevelBorder.LOWERED));

        comboBox.addItemListener(new ItemListener() {

            public void itemStateChanged (ItemEvent event)
            {
                String[] items = { "A", "B", "C", "D", "E", "F" };
                final DefaultComboBoxModel model = new DefaultComboBoxModel(
                        items);

                comboBox.setModel(model);

            }
        });

        getContentPane().add(comboBox);
        getContentPane().add(textArea);
    }

    public static void main (String[] args)
    {
        SwingUtilities.invokeLater(new Runnable() {
            public void run ()
            {
                new ComboBoxSelectionChange().setVisible(true);
            }
        });
    }
}

Answer 1

尝试向 JComboBox 添加弹出菜单监听器，如下所示:

comboBox.addPopupMenuListener( PopupMenuListener listener )
{

   protected void popupMenuWillBecomeVisible( PopupMenuEvent event )
   {
       //update your model
   }

}