An applet that counts down from a specified time
/*
* Copyright (c) 2004 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book,
* please visit http://www.davidflanagan.com/javaexamples3.
*/
import java.applet.AudioClip;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.net.MalformedURLException;
import java.net.URL;
import java.text.NumberFormat;
import javax.swing.ImageIcon;
import javax.swing.JApplet;
import javax.swing.JLabel;
import javax.swing.SwingConstants;
import javax.swing.Timer;
/**
* An applet that counts down from a specified time. When it reaches 00:00, it
* optionally plays a sound and optionally moves the browser to a new page.
* Place the mouse over the applet to pause the count; move it off to resume.
* This class demonstrates most applet methods and features.
*/
public class Countdown extends JApplet implements ActionListener, MouseListener {
long remaining; // How many milliseconds remain in the countdown.
long lastUpdate; // When count was last updated
JLabel label; // Displays the count
Timer timer; // Updates the count every second
NumberFormat format; // Format minutes:seconds with leading zeros
Image image; // Image to display along with the time
AudioClip sound; // Sound to play when we reach 00:00
// Called when the applet is first loaded
public void init() {
// Figure out how long to count for by reading the "minutes" parameter
// defined in a <param> tag inside the <applet> tag. Convert to ms.
String minutes = getParameter("minutes");
if (minutes != null)
remaining = Integer.parseInt(minutes) * 60000;
else
remaining = 600000; // 10 minutes by default
// Create a JLabel to display remaining time, and set some properties.
label = new JLabel();
label.setHorizontalAlignment(SwingConstants.CENTER);
label.setOpaque(true); // So label draws the background color
// Read some parameters for this JLabel object
String font = getParameter("font");
String foreground = getParameter("foreground");
String background = getParameter("background");
String imageURL = getParameter("image");
// Set label properties based on those parameters
if (font != null)
label.setFont(Font.decode(font));
if (foreground != null)
label.setForeground(Color.decode(foreground));
if (background != null)
label.setBackground(Color.decode(background));
if (imageURL != null) {
// Load the image, and save it so we can release it later
image = getImage(getDocumentBase(), imageURL);
// Now display the image in the JLabel.
label.setIcon(new ImageIcon(image));
}
// Now add the label to the applet. Like JFrame and JDialog, JApplet
// has a content pane that you add children to
getContentPane().add(label, BorderLayout.CENTER);
// Get an optional AudioClip to play when the count expires
String soundURL = getParameter("sound");
if (soundURL != null)
sound = getAudioClip(getDocumentBase(), soundURL);
// Obtain a NumberFormat object to convert number of minutes and
// seconds to strings. Set it up to produce a leading 0 if necessary
format = NumberFormat.getNumberInstance();
format.setMinimumIntegerDigits(2); // pad with 0 if necessary
// Specify a MouseListener to handle mouse events in the applet.
// Note that the applet implements this interface itself
addMouseListener(this);
// Create a timer to call the actionPerformed() method immediately,
// and then every 1000 milliseconds. Note we don't start the timer yet.
timer = new Timer(1000, this);
timer.setInitialDelay(0); // First timer is immediate.
}
// Free up any resources we hold; called when the applet is done
public void destroy() {
if (image != null)
image.flush();
}
// The browser calls this to start the applet running
// The resume() method is defined below.
public void start() {
resume();
} // Start displaying updates
// The browser calls this to stop the applet. It may be restarted later.
// The pause() method is defined below
public void stop() {
pause();
} // Stop displaying updates
// Return information about the applet
public String getAppletInfo() {
return "Countdown applet Copyright (c) 2003 by David Flanagan";
}
// Return information about the applet parameters
public String[][] getParameterInfo() {
return parameterInfo;
}
// This is the parameter information. One array of strings for each
// parameter. The elements are parameter name, type, and description.
static String[][] parameterInfo = {
{ "minutes", "number", "time, in minutes, to countdown from" },
{ "font", "font", "optional font for the time display" },
{ "foreground", "color", "optional foreground color for the time" },
{ "background", "color", "optional background color" },
{ "image", "image URL", "optional image to display next to countdown" },
{ "sound", "sound URL", "optional sound to play when we reach 00:00" },
{ "newpage", "document URL", "URL to load when timer expires" }, };
// Start or resume the countdown
void resume() {
// Restore the time we're counting down from and restart the timer.
lastUpdate = System.currentTimeMillis();
timer.start(); // Start the timer
}
// Pause the countdown
void pause() {
// Subtract elapsed time from the remaining time and stop timing
long now = System.currentTimeMillis();
remaining -= (now - lastUpdate);
timer.stop(); // Stop the timer
}
// Update the displayed time. This method is called from actionPerformed()
// which is itself invoked by the timer.
void updateDisplay() {
long now = System.currentTimeMillis(); // current time in ms
long elapsed = now - lastUpdate; // ms elapsed since last update
remaining -= elapsed; // adjust remaining time
lastUpdate = now; // remember this update time
// Convert remaining milliseconds to mm:ss format and display
if (remaining < 0)
remaining = 0;
int minutes = (int) (remaining / 60000);
int seconds = (int) ((remaining % 60000) / 1000);
label.setText(format.format(minutes) + ":" + format.format(seconds));
// If we've completed the countdown beep and display new page
if (remaining == 0) {
// Stop updating now.
timer.stop();
// If we have an alarm sound clip, play it now.
if (sound != null)
sound.play();
// If there is a newpage URL specified, make the browser
// load that page now.
String newpage = getParameter("newpage");
if (newpage != null) {
try {
URL url = new URL(getDocumentBase(), newpage);
getAppletContext().showDocument(url);
} catch (MalformedURLException ex) {
showStatus(ex.toString());
}
}
}
}
// This method implements the ActionListener interface.
// It is invoked once a second by the Timer object
// and updates the JLabel to display minutes and seconds remaining.
public void actionPerformed(ActionEvent e) {
updateDisplay();
}
// The methods below implement the MouseListener interface. We use
// two of them to pause the countdown when the mouse hovers over the timer.
// Note that we also display a message in the statusline
public void mouseEntered(MouseEvent e) {
pause(); // pause countdown
showStatus("Paused"); // display statusline message
}
public void mouseExited(MouseEvent e) {
resume(); // resume countdown
showStatus(""); // clear statusline
}
// These MouseListener methods are unused.
public void mouseClicked(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
}
public void mouseReleased(MouseEvent e) {
}
}
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