jcomboboxdemo.java

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import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class JComboBoxDemo extends JFrame 
{
    private JComboBox comboBox;
    private JLabel label;
    private String names[] = {"北京", "上海", "南京", "武汉"};
    
	public JComboBoxDemo() 
	{
		super("下拉列表");
		setSize(200, 150);       
		try
		{   //设置外观
			UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
		}catch(Exception e){}
		
    //获取内容面板
		Container container = getContentPane();
		//设置内容面板的布局管理器
		container.setLayout(new FlowLayout());
		container.setBackground(Color.YELLOW);
		
		//创建下拉列表
		comboBox = new JComboBox(names);
		//设置用户单击下拉列表时所能显示的列表项的最大数目
		comboBox.setMaximumRowCount(3);
		//设置默认的选择项
		comboBox.setSelectedIndex(0);
		//设置字体
		comboBox.setFont(new Font("Serif", Font.PLAIN, 14));
		//注册监听器
		comboBox.addItemListener(new ComboBoxHandler());
		
		//创建标签
		label = new JLabel("你选择了: 北京");
	    label.setFont(new Font("Serif", Font.PLAIN, 14));
		
		container.add(comboBox);
		container.add(label);
		
		setVisible(true);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
	
	public static void main(String[] args) 
	{
		JComboBoxDemo application = new JComboBoxDemo();
	}
	
	private class ComboBoxHandler implements ItemListener
	{
		public void itemStateChanged(ItemEvent event)
		{
		    if(event.getStateChange() == event.SELECTED)
		    {
		    	label.setText("你选择了: " + names[comboBox.getSelectedIndex()]);
		    }
		}
	}
}