第2周：Java事件处理

源程序1simpleEvent.javaimport java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class simpleEvent extends Applet implements ActionListener
{
Label lb;
TextField in,out;
public void init()
{
lb = new Label("请输入你的名字");
in = new TextField(6); //创建输入文本框
out = new TextField(20); //创建输出文本框
add(lb);
add(in);
add(out);
in.addActionListener(this); //将文本框注册给文本事件的监听者
}
public void actionPerformed(ActionEvent e) //执行动作
{
out.setText(in.getText() + "欢迎光临");
}

}

运行结果：



源程序2ButtonDemo.java

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class ButtonDemo extends Applet implements ActionListener
{
String msg ="";
public void init()
{
Button yes = new Button("是");
Button no =new Button("否");
Button maybe = new Button("取消");
add(yes);
add(no);
add(maybe);
yes.addActionListener(this);
no.addActionListener(this);
maybe.addActionListener(this);
}
public void actionPerformed(ActionEvent e)
{
String str = e.getActionCommand();
if(str == "是")
{
msg = "你单击了按钮'是'。";
}
else if(str == "否")
{
msg = "你单击了按钮'否'。";
}
else
{
msg = "你单击了按钮'取消'。";
}
repaint();
}
public void paint(Graphics g)
{
g.drawString(msg,6,100);
}

}

运行结果：