Java程序显示正在运行的时钟(timer类)

(本程序主要来自Java语言程序设计（基础篇）(Y.Daniel Liang))

类javax.swing.Timer是一个按照预定频率触发ActionEvent事件的源组件。一个Timer对象可以作为ActionEvent事件的源，监听器必须是ActionListener的实例并且要用Timer对象注册。利用给定的时延和监听器可以使用它唯一的构造方法创建Timer对象其中时延是两个事件行为之间间隔的毫秒数。可以使用addActionListener方法添加其他监听器，用setDelay方法调整时延。用start()方法开始，stop()方法停止。

效果图

首先是ClockAnimation类

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

public class ClockAnimation extends StillClock{
    public ClockAnimation(){
        //创建Timer对象
        Timer timer=new Timer(1000,new TimerLisener());
        timer.start();
    }
    private class TimerLisener implements ActionListener{
        //创建相关监听器
        public void actionPerformed(ActionEvent arg0) {
            setCurrentTime();
            repaint();
        }
    }
    
    public static void main(String[] args){
        JFrame frame = new JFrame("ClockAnimation");
        ClockAnimation clock=new ClockAnimation();
        frame.add(clock);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(200,200);
        frame.setVisible(true);
    }

}

 StillClock类是（继承Jpanel）：

import java.awt.*;
import java.util.*;
import javax.swing.*;

public class StillClock extends JPanel{
    private int hour;
    private int minute;
    private int second;
    
    public StillClock(){
        setCurrentTime();
    }
    
    public StillClock(int hour,int minute,int second){
        this.hour=hour;
        this.minute=minute;
        this.second=second;
    }
    
    public int getHour(){
        return hour;
    }
    
    public void setHour(int hour){
        this.hour=hour;
        repaint();
    }
    
    public int getMinute(){
        return minute;
    }
    public void setMinute(int minute){
        this.minute = minute;
        repaint();
    }
    public int getSecond(){
        return second;
    }
    public void setSecond(){
        this.second=second;
        repaint();
    }
    
    protected void paintComponent(Graphics g){
        
        super.paintComponent(g);
        
        int clockRadius=(int)(Math.min(getWidth(), getHeight())*0.4);//*0.8*0.5);
        int xCenter=getWidth()/2;
        int yCenter=getHeight()/2;
        //System.out.println(clockRadius);
        g.setColor(Color.black);
        g.drawOval(xCenter-clockRadius, yCenter-clockRadius, 2*clockRadius, 2*clockRadius);
        g.drawString("12", xCenter-5, yCenter-clockRadius+12);
        g.drawString("9", xCenter-clockRadius+3, yCenter+5);
        g.drawString("3", xCenter+clockRadius-10, yCenter+3);
        g.drawString("6", xCenter-3, yCenter+clockRadius-3);
        
        //draw second hand
        int sLength=(int)(clockRadius*0.8);
        int xSecond=(int)(xCenter+sLength*Math.sin(second*(2*Math.PI/60)));
        int ySecond=(int)(yCenter-sLength*Math.cos(second*(2*Math.PI/60)));
        g.setColor(Color.red);
        g.drawLine(xCenter, yCenter, xSecond, ySecond);
        
        //draw minute hand
        int mLength=(int)(clockRadius*0.65);
        int xMinute=(int)(xCenter+mLength*Math.sin(minute*(2*Math.PI/60)));
        int yMinute=(int)(yCenter-mLength*Math.cos(minute*(2*Math.PI/60)));
        g.setColor(Color.blue);
        g.drawLine(xCenter, yCenter, xMinute, yMinute);
        
        //draw hour hand
        int hLength=(int)(clockRadius*0.5);
        int xHour=(int)(xCenter+hLength*Math.sin((hour%12+minute/60.0)*(2*Math.PI/12)));
        int yHour=(int)(yCenter-hLength*Math.cos((hour%12+minute/60.0)*(2*Math.PI/12)));
        g.setColor(Color.black);
        g.drawLine(xCenter, yCenter, xHour, yHour);
    }
    
    public void setCurrentTime(){
        Calendar calendar = new GregorianCalendar();
        this.hour=calendar.get(Calendar.HOUR_OF_DAY);
        this.minute=calendar.get(Calendar.MINUTE);
        this.second=calendar.get(Calendar.SECOND);
    }
}