清华大学：JAVA教学课件：8-2

程序8-2：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class JButtonExample2 extends WindowAdapter
implements ActionListener {
JFrame f;
JPanel p;
JButton b1,b2;
JTextField tf;
int tag = 0;
public static void main(String args[]) {
JButtonExample2 be = new JButtonExample2();
be.go();
}
public void go() {
f = new JFrame("JButton Example2");
b1 = new JButton("Sample");
b1.setMnemonic(KeyEvent.VK_S); //设置快捷键
b1.setActionCommand("Sample"); //设置命令名
b1.addActionListener(this);

b2 = new JButton("Disable Sample");
b2.setMnemonic(KeyEvent.VK_A); //设置快捷键
b2.setActionCommand("disable"); //设置命令名
b2.addActionListener(this);

p = new JPanel();
p.add(b1);
p.add(b2);

f.getContentPane().add(p,"South");

tf = new JTextField();
f.getContentPane().add(tf,"Center");

f.addWindowListener(this);
f.setSize(300,150);
f.setVisible(true);
}
// 实现ActionListener接口中的actionPerformed()方法
public void actionPerformed(ActionEvent e) {
String s1 = "You have pressed the Button!";
String s2 = "You do another time!";

// 根据命令名进行判断
if (e.getActionCommand()=="Sample") {
if (tag==0) {
tf.setText(s1);
tag = 1;
} else {
tf.setText(s2);
tag = 0;
}
}
if (e.getActionCommand()=="disable") {
b1.setEnabled(false); //设置Sample按钮为不可用
b2.setText("Enable Sample"); //修改显示文本
b2.setActionCommand("enable"); //修改命令名
}
if (e.getActionCommand()=="enable") {
b1.setEnabled(true); //设置Sample按钮为可用
b2.setText("Disable Sample");
b2.setActionCommand("disable");
}
}
// 重载WindowAdapter类中的windowClosing()方法
public void windowClosing(WindowEvent e) {
// 结束程序运行
System.exit(0);
}
}