MyFrame.java

package swing;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.Date;

public class MyFrame extends JFrame {
    JLabel timeLabel= new JLabel("00:00:00");
    JButton button=new
 
 JButton("顯示時間");

    public MyFrame(String title){
        super(title);
        //內容面板
        Container contentPane=getContentPane();
        contentPane.setLayout(new FlowLayout());

        //向內容面板新增控制元件
        contentPane.add(button);
        contentPane.add(timeLabel);
        //創造監聽器物件
        //把監聽器註冊給按鈕
 

        button.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e) {
                //當按鈕被點選時，Swing框架會呼叫監聽器的actionPerformed()方法
                System.out.println("按鈕被點選....");
                showTime();
            }
        });

    }
    
 
public void showTime(){
        SimpleDateFormat sdf=new SimpleDateFormat("HH:mm:ss");
        String timestr=sdf.format(new Date());
        timeLabel.setText(timestr);
        System.out.println("時間已更新");
    }
}
package swing;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.Date;

public class MyFrame extends JFrame {
    JLabel timeLabel= new JLabel("00:00:00");
    JButton button=new JButton("顯示時間");

    public MyFrame(String title){
        super(title);
        //內容面板
        Container contentPane=getContentPane();
        contentPane.setLayout(new FlowLayout());

        //向內容面板新增控制元件
        contentPane.add(button);
        contentPane.add(timeLabel);
        //創造監聽器物件
        //把監聽器註冊給按鈕
        button.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e) {
                //當按鈕被點選時，Swing框架會呼叫監聽器的actionPerformed()方法
                System.out.println("按鈕被點選....");
                showTime();
            }
        });

    }
    public void showTime(){
        SimpleDateFormat sdf=new SimpleDateFormat("HH:mm:ss");
        String timestr=sdf.format(new Date());
        timeLabel.setText(timestr);
        System.out.println("時間已更新");
    }
}

SwingDemo.java

package swing;

import javax.swing.*;

public class SwingDemo {
    private static void createGUI(){

        //JFrame指一個視窗，構造方法的引數為視窗標題
        MyFrame frame=new MyFrame("swing demo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //設定視窗的其它引數，如視窗大小
        frame.setSize(400,300);

        //顯示視窗
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                createGUI();
            }
        });
    }
}