timertest.java

Java核心技术卷2 配套源代码 绝对全和经典

/**
   @version 1.21 2003-09-09
   @author Cay Horstmann 
*/

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

/**
   This class shows a frame with several clocks that
   are updated by a timer thread.
*/
public class TimerTest
{  
   public static void main(String[] args)
   {  
      TimerTestFrame frame = new TimerTestFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.show();
   }
}

/**
   The frame holding the clocks.
*/
class TimerTestFrame extends JFrame
{  
   public TimerTestFrame()
   {  
      setTitle("TimerTest");
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

      Container c = getContentPane();
      c.setLayout(new GridLayout(2, 3));
      c.add(new ClockCanvas("America/Los_Angeles"));
      c.add(new ClockCanvas("America/New_York"));
      c.add(new ClockCanvas("America/Caracas"));
      c.add(new ClockCanvas("Europe/Rome"));
      c.add(new ClockCanvas("Africa/Cairo"));
      c.add(new ClockCanvas("Asia/Taipei"));
   }

   public static final int DEFAULT_WIDTH = 450;
   public static final int DEFAULT_HEIGHT = 300;
}

/**
   The canvas to display a clock that is updated by a timer.
*/
class ClockCanvas extends JPanel
{ 
   /**
      Constructs a clock canvas.
      @param tz the time zone string
   */
   public ClockCanvas(String tz)
   {  
      zone = tz;
      calendar = new GregorianCalendar(TimeZone.getTimeZone(tz));
      Timer t = new Timer(1000, new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               calendar.setTime(new Date());
               repaint();
            }
         });
      t.start();
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
   }

   public void paintComponent(Graphics g)
   {  
      super.paintComponent(g);
      g.drawOval(0, 0, 100, 100);

      int seconds = calendar.get(Calendar.HOUR) * 60 * 60
         + calendar.get(Calendar.MINUTE) * 60
         + calendar.get(Calendar.SECOND);
      double hourAngle = 2 * Math.PI
         * (seconds - 3 * 60 * 60) / (12 * 60 * 60);
      double minuteAngle = 2 * Math.PI
         * (seconds - 15 * 60) / (60 * 60);
      double secondAngle = 2 * Math.PI
         * (seconds - 15) / 60;
      g.drawLine(50, 50, 50 + (int)(30
         * Math.cos(hourAngle)),
         50 + (int)(30 * Math.sin(hourAngle)));
      g.drawLine(50, 50, 50 + (int)(40
         * Math.cos(minuteAngle)),
         50 + (int)(40 * Math.sin(minuteAngle)));
      g.drawLine(50, 50, 50 + (int)(45
         * Math.cos(secondAngle)),
         50 + (int)(45 * Math.sin(secondAngle)));
      g.drawString(zone, 0, 115);
   }

   private String zone;
   private GregorianCalendar calendar;

   public static final int DEFAULT_WIDTH = 125;
   public static final int DEFAULT_HEIGHT = 125;
}