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This is the same as Example - Text Clock, but defines a reusable component for the clock. See javax.swing.Timer for an explanation of a simple timer class. |
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// File: textclock/TextClock2.java
// Description: Application / Applet for a simple text clock.
// Author: Fred Swartz
// Date: 2005-02-15, 1999-05-01, 2001-11-02, 2002-11-07
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
///////////////////////////////////////////////////////////// TextClock2
public class TextClock2 extends JApplet {
//====================================================== constructor
public TextClock2() {
add(new Clock());
}
//============================================================= main
public static void main(String[] args) {
JFrame window = new JFrame("Time of Day");
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setContentPane(new Clock());
window.pack();
window.setVisible(true);
System.out.println(window.getContentPane().size());
}
}
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This text clock component is created by subclassing JTextField. Whether this is better than making it a part of a JPanel is debatable, as it goes against the principle that one should Favor Composition over Inheritance.
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// File: textclock/Clock.java
// Description: This implements a text clock by subclassing
// JTextField, changing its appearance and
// adding a timer to update itself.
// Regarding subclassing JTextField
// PROS: It's simple.
// All JTextField methods are available
// to the user, so they can easily
// customize it (fonts, colors, ...);
// CONS: It can't become more complicated, eg,
// to add buttons, etc. because the
// users may already be using the
// JTextField methods.
// Author: Fred Swartz,
// Date: 15 Feb 2005
// Possible Enhancements:
// Appearance: center, leading zeros, uneditable,
// Function: 12/24 hour, alarm, timer, stop and start.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Calendar;
///////////////////////////////////////////////////////////// Clock
class Clock extends JTextField {
javax.swing.Timer m_t;
//================================================== constructor
public Clock() {
//... Set some attributes.
setColumns(6);
setFont(new Font("sansserif", Font.PLAIN, 48));
//... Create a 1-second timer.
m_t = new javax.swing.Timer(1000, new ClockTickAction());
m_t.start(); // Start the timer
}
/////////////////////////////////////////// inner class listener
private class ClockTickAction implements ActionListener {
public void actionPerformed(ActionEvent e) {
//... Get the current time.
Calendar now = Calendar.getInstance();
int h = now.get(Calendar.HOUR_OF_DAY);
int m = now.get(Calendar.MINUTE);
int s = now.get(Calendar.SECOND);
setText("" + h + ":" + m + ":" + s);
}
}
}
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