trylist2.java

非常好的JAVA学习资料

package twotrylist;

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

public class TryList2 extends Applet {
  List l=new List(6,false);              //定义一个只支持单项选择的滚动表
  TextField tf=new TextField(15);
  TextField tf1=new TextField(15);
  Label la1=new Label("action:");
  Label la2=new Label("item:");
  Panel p=new Panel();
  String[] description = { "red","blue","yellow" };
  int count=0;

  public void init() {
    tf.setEditable(false); //将文本域设置为不可编辑，即禁止输入
    tf1.setEditable(false);
    for(int i = 0; i < 3; i++)
      l.addItem(description[count++]); //加入滚动表中的选项
    p.add(la1);   //将标签、文本域加入面板
    p.add(tf);
    p.add(la2);
    p.add(tf1);
    add(p);    //显示面板
    add(l);    //显示滚动表
    l.addActionListener(new ListenActionItem());  //设置动作事件的监听者
    l.addItemListener(new ListenActionItem());   //设置选项事件的监听者
  }

  class ListenActionItem implements ActionListener,ItemListener {//动作事件发生时在文本域中tf显示提示信息
    public void actionPerformed ( ActionEvent e ) {
       if ( e.getActionCommand()== "red" )  
//用ActionEvent对象的getActionCommand( )方法取得与引发事件相关的字符串
           tf.setText("red double-clicked");
       else if ( e.getActionCommand()== "blue" )
           tf.setText("blue double-clicked");
       else if ( e.getActionCommand()== "yellow" )
           tf.setText("yellow double-clicked");
    }
 
    public void itemStateChanged (ItemEvent e) {
       String source=l.getSelectedItem();  //取得被选中内容
       if ( source == "red" ){
         //if ( e.getStateChange()==e.SELECTED )
            tf1.setText("red selected");
         //else tf.setText("red deselected");   
//若为多项选择可用if语句判断是被选上还是去掉选择
       }
       else if ( source == "blue" ){
            tf1.setText("blue selected");
       }
       else if ( source == "yellow" ){
            tf1.setText("yellow selected");
       }
    }
}
}