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Java中如何實(shí)現(xiàn)顯示動(dòng)態(tài)的時(shí)間
本文所述實(shí)例可以實(shí)現(xiàn)Java在界面上動(dòng)態(tài)的顯示時(shí)間。具體實(shí)現(xiàn)方法匯總?cè)缦拢?/p>
1.方法一 用TimerTask：
利用java.util.Timer和java.util.TimerTask來(lái)做動(dòng)態(tài)更新，畢竟每次更新可以看作是計(jì)時(shí)1秒發(fā)生一次。
代碼如下：
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 the time per second */ private void configTimeArea() { Timer tmr = new Timer(); tmr.scheduleAtFixedRate(new JLabelTimerTask(),new Date(), ONE_SECOND); } /** * Timer task to 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); } }
繼承TimerTask來(lái)創(chuàng)建一個(gè)自定義的task，獲取當(dāng)前時(shí)間，更新displayArea.
然后創(chuàng)建一個(gè)timer的實(shí)例，每1秒執(zhí)行一次timertask。由于用schedule可能會(huì)有時(shí)間誤差產(chǎn)生，所以直接調(diào)用精度更高的scheduleAtFixedRate的。
2. 方法二：利用線程：
這個(gè)就比較簡(jiǎn)單了。具體代碼如下：
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(); } }
比較：
個(gè)人傾向于方法一，因?yàn)門(mén)imer是可以被多個(gè)TimerTask共用，而產(chǎn)生一個(gè)線程，會(huì)增加多線程的維護(hù)復(fù)雜度。
注意如下代碼：
jFrame.setDefaultCloseOperation(); // 給關(guān)閉按鈕增加特定行為jFrame.setLocationRelativeTo(null); // 讓Frame一出來(lái)就在屏幕中間，而不是左上方。
將上面方法一稍微一修改，就可以顯示多國(guó)時(shí)間。代碼如下：
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 the time per second */ private void configTimeArea() { Timer tmr = new Timer(); tmr.scheduleAtFixedRate(new JLabelTimerTask(),new Date(), ONE_SECOND); } /** * Timer task to 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(); } }
本來(lái)需要在updateTimeZone(TimeZone newZone)中，更新displayArea的。但是考慮到TimerTask執(zhí)行的時(shí)間太短，才1秒鐘，以肉眼觀察，基本上是和立刻更新沒(méi)區(qū)別。如果TimerTask執(zhí)行時(shí)間長(zhǎng)的話(huà)，這里就要立刻重新用心的時(shí)間更新一下displayArea。
補(bǔ)充：
①. pack() 用來(lái)自動(dòng)計(jì)算屏幕大�。�
�、�. TimeZone.getAvailableIDs() 用來(lái)獲取所有的TimeZone。
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