choicedemo.java

java中awt应用的例子

import java.awt.*;
import java.awt.event.*;

public class ChoiceDemo extends Frame 
                        implements ItemListener {
    Choice choice; 
    Label label;

    public ChoiceDemo(String title){
    	super(title);
    }
    
    public void creat() {
        choice = new Choice();  //创建下拉式列表。
        choice.addItem("First");
        choice.addItem("Second");
        choice.addItem("Third");
        choice.addItem("Fourth");

        choice.addItemListener(this);  //注册ItemEvent事件监听器。

        label = new Label();
        setLabelText(choice.getSelectedIndex(), 
                     choice.getSelectedItem());

        //向Frame中增加两个组件。 
        setLayout(new FlowLayout());
        add(choice);
        add(label);
        addWindowListener(new WindowAdapter(){
        	public void windowClosing(WindowEvent e){
        		System.exit(0);
        	}
        });
        setSize(400,100);
        setVisible(true);
    }

    //更新Label的内容。
    void setLabelText(int num, String text) {
        label.setText("Item #" + num + " selected. "
                    + "Text = \"" + text + "\".");
    }
    
    //ItemListener的事件处理方法。
    public void itemStateChanged(ItemEvent e) {
        setLabelText(choice.getSelectedIndex(),
                     choice.getSelectedItem());
    }
    
   public static void main(String[] args){
   		ChoiceDemo cd = new ChoiceDemo("Choice test");
   		cd.creat();
   	}
}