时间动态显示

来源：互联网发布：mysql regexp使用编辑：程序博客网时间：2024/06/05 12:07

目标：在界面上动态的显示时间。

KeyWord/关键词：Java Swing, Thread, Timer, TimerTask

1.方法一用TimerTask

利用java.util.Timer和java.util.TimerTask来做动态更新，毕竟每次更新可以看作是计时1秒发生一次。

代码如下：

import java.awt.Dimension;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
/**
* This class is a simple JFrame implementation to explain how to
* display time dynamically on the JSwing-based interface.
* @author Edison
*
*/
public class TimeFrame extends JFrame
{
/*
* Variables
*/
private JPanel timePanel;
private JLabel timeLabel;
private JLabel displayArea;
private String DEFAULT_TIME_FORMAT = "HH:mm:ss";
private String time;
private int ONE_SECOND = 1000;

public TimeFrame()
{
  timePanel = new JPanel();
  timeLabel = new JLabel("CurrentTime: ");
  displayArea = new JLabel();

  configTimeArea();

  timePanel.add(timeLabel);
  timePanel.add(displayArea);
  this.add(timePanel);
  this.setDefaultCloseOperation(EXIT_ON_CLOSE);
  this.setSize(new Dimension(200,70));
  this.setLocationRelativeTo(null);
}

/**
* This method creates a timer task to update the time per second
*/
private void configTimeArea() {
  Timer tmr = new Timer();
  tmr.scheduleAtFixedRate(new JLabelTimerTask(),new Date(), ONE_SECOND);
}

/**
* Timer task to update the time display area
*
*/
protected class JLabelTimerTask extends TimerTask{
  SimpleDateFormat dateFormatter = new SimpleDateFormat(DEFAULT_TIME_FORMAT);
  @Override
  public void run() {
   time = dateFormatter.format(Calendar.getInstance().getTime());
   displayArea.setText(time);
  }
}

public static void main(String arg[])
{
TimeFrame timeFrame=new TimeFrame();
timeFrame.setVisible(true);
}
}

继承TimerTask来创建一个自定义的task，获取当前时间，更新displayArea.

然后创建一个timer的实例，每1秒执行一次timertask。由于用schedule可能会有时间误差产生，所以直接调用精度更高的scheduleAtFixedRate的。

2. 方法二：利用线程

这个就比较简单了。

import java.awt.Dimension;
import java.text.SimpleDateFormat;
import java.util.Calendar;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

/**
* This class is a simple JFrame implementation to explain how to
* display time dynamically on the JSwing-based interface.
* @author Edison
*
*/
public class DTimeFrame2 extends JFrame implements Runnable{
private JFrame frame;
private JPanel timePanel;
private JLabel timeLabel;
private JLabel displayArea;
private String DEFAULT_TIME_FORMAT = "HH:mm:ss";
private int ONE_SECOND = 1000;

public DTimeFrame2()
{
  timePanel = new JPanel();
  timeLabel = new JLabel("CurrentTime: ");
  displayArea = new JLabel();

  timePanel.add(timeLabel);
  timePanel.add(displayArea);
  this.add(timePanel);
  this.setDefaultCloseOperation(EXIT_ON_CLOSE);
  this.setSize(new Dimension(200,70));
  this.setLocationRelativeTo(null);
}

public void run()
{
  while(true)
  {
   SimpleDateFormat dateFormatter = new SimpleDateFormat(DEFAULT_TIME_FORMAT);
   displayArea.setText(dateFormatter.format(
         Calendar.getInstance().getTime()));
   try
   {
    Thread.sleep(ONE_SECOND);
   }
   catch(Exception e)
   {
    displayArea.setText("Error!!!");
   }
  }
}

public static void main(String arg[])
{
  DTimeFrame2 df2=new DTimeFrame2();
  df2.setVisible(true);

  Thread thread1=new Thread(df2);
  thread1.start();
}
}

比较：

个人倾向于方法一，因为Timer是可以被多个TimerTask共用，而产生一个线程，会增加多线程的维护复杂度。

TIPS：

jFrame.setDefaultCloseOperation(); // 给关闭按钮增加特定行为

jFrame.setLocationRelativeTo(null); // 让Frame一出来就在屏幕中间，而不是左上方。

将上面方法一稍微一修改，就可以显示多国时间。代码如下：

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;
import java.util.Timer;
import java.util.TimerTask;

import javax.swing.DefaultComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
/**
* A simple world clock
* @author Edison
*
*/
public class WorldTimeFrame extends JFrame
{
/**
*
*/
private static final long serialVersionUID = 4782486524987801209L;

private String time;
private JPanel timePanel;
private TimeZone timeZone;
private JComboBox zoneBox;
private JLabel displayArea;

private int ONE_SECOND = 1000;
private String DEFAULT_FORMAT = "EEE d MMM, HH:mm:ss";

public WorldTimeFrame()
{
  zoneBox = new JComboBox();
  timePanel = new JPanel();
  displayArea = new JLabel();
  timeZone = TimeZone.getDefault();

  zoneBox.setModel(new DefaultComboBoxModel(TimeZone.getAvailableIDs()));

  zoneBox.addActionListener(new ActionListener(){
   @Override
   public void actionPerformed(ActionEvent e) {
    updateTimeZone(TimeZone.getTimeZone((String) zoneBox.getSelectedItem()));
   }

  });

  configTimeArea();

  timePanel.add(displayArea);
  this.setLayout(new BorderLayout());
  this.add(zoneBox, BorderLayout.NORTH);
  this.add(timePanel, BorderLayout.CENTER);
  this.setLocationRelativeTo(null);
  this.setDefaultCloseOperation(EXIT_ON_CLOSE);
  this.setVisible(true);
  pack();
}

/**
* This method creates a timer task to update the time per second
*/
private void configTimeArea() {
  Timer tmr = new Timer();
  tmr.scheduleAtFixedRate(new JLabelTimerTask(),new Date(), ONE_SECOND);
}

/**
* Timer task to update the time display area
*
*/
public class JLabelTimerTask extends TimerTask{
SimpleDateFormat dateFormatter = new SimpleDateFormat(DEFAULT_FORMAT, Locale.ENGLISH);
@Override
public void run() {
   dateFormatter.setTimeZone(timeZone);
   time = dateFormatter.format(Calendar.getInstance().getTime());
   displayArea.setText(time);
}
}

/**
* Update the timeZone
* @param newZone
*/
public void updateTimeZone(TimeZone newZone)
{
  this.timeZone = newZone;
}

public static void main(String arg[])
{
  new WorldTimeFrame();
}
}

TBD:

本来需要在updateTimeZone(TimeZone newZone)中，更新displayArea的。但是考虑到TimerTask执行的时间太短，才1秒钟，以肉眼观察，基本上是和立刻更新没区别。如果TimerTask执行时间长的话，这里就要立刻重新用心的时间更新一下displayArea。

TIPS：

a. pack() 用来自动计算屏幕大小；

b. TimeZone.getAvailableIDs() 用来获取所有的TimeZone。