ProgressBar Demo: long task
/* From http://java.sun.com/docs/books/tutorial/index.html */
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* This software is provided "AS IS," without a warranty of any kind. ALL
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import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/*
* ProgressBarDemo.java is a 1.4 application that requires these files:
* LongTask.java
* SwingWorker.java
*/
public class ProgressBarDemo extends JPanel
implements ActionListener {
public final static int ONE_SECOND = 1000;
private JProgressBar progressBar;
private Timer timer;
private JButton startButton;
private LongTask task;
private JTextArea taskOutput;
private String newline = "\n";
public ProgressBarDemo() {
super(new BorderLayout());
task = new LongTask();
//Create the demo's UI.
startButton = new JButton("Start");
startButton.setActionCommand("start");
startButton.addActionListener(this);
progressBar = new JProgressBar(0, task.getLengthOfTask());
progressBar.setValue(0);
progressBar.setStringPainted(true);
taskOutput = new JTextArea(5, 20);
taskOutput.setMargin(new Insets(5,5,5,5));
taskOutput.setEditable(false);
taskOutput.setCursor(null); //inherit the panel's cursor
//see bug 4851758
JPanel panel = new JPanel();
panel.add(startButton);
panel.add(progressBar);
add(panel, BorderLayout.PAGE_START);
add(new JScrollPane(taskOutput), BorderLayout.CENTER);
setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
//Create a timer.
timer = new Timer(ONE_SECOND, new ActionListener() {
public void actionPerformed(ActionEvent evt) {
progressBar.setValue(task.getCurrent());
String s = task.getMessage();
if (s != null) {
taskOutput.append(s + newline);
taskOutput.setCaretPosition(
taskOutput.getDocument().getLength());
}
if (task.isDone()) {
Toolkit.getDefaultToolkit().beep();
timer.stop();
startButton.setEnabled(true);
setCursor(null); //turn off the wait cursor
progressBar.setValue(progressBar.getMinimum());
}
}
});
}
/**
* Called when the user presses the start button.
*/
public void actionPerformed(ActionEvent evt) {
startButton.setEnabled(false);
setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
task.go();
timer.start();
}
/**
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createAndShowGUI() {
//Make sure we have nice window decorations.
JFrame.setDefaultLookAndFeelDecorated(true);
//Create and set up the window.
JFrame frame = new JFrame("ProgressBarDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create and set up the content pane.
JComponent newContentPane = new ProgressBarDemo();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);
//Display the window.
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
class LongTask {
private int lengthOfTask;
private int current = 0;
private boolean done = false;
private boolean canceled = false;
private String statMessage;
public LongTask() {
//Compute length of task...
//In a real program, this would figure out
//the number of bytes to read or whatever.
lengthOfTask = 1000;
}
/**
* Called from ProgressBarDemo to start the task.
*/
public void go() {
final SwingWorker worker = new SwingWorker() {
public Object construct() {
current = 0;
done = false;
canceled = false;
statMessage = null;
return new ActualTask();
}
};
worker.start();
}
/**
* Called from ProgressBarDemo to find out how much work needs
* to be done.
*/
public int getLengthOfTask() {
return lengthOfTask;
}
/**
* Called from ProgressBarDemo to find out how much has been done.
*/
public int getCurrent() {
return current;
}
public void stop() {
canceled = true;
statMessage = null;
}
/**
* Called from ProgressBarDemo to find out if the task has completed.
*/
public boolean isDone() {
return done;
}
/**
* Returns the most recent status message, or null
* if there is no current status message.
*/
public String getMessage() {
return statMessage;
}
/**
* The actual long running task. This runs in a SwingWorker thread.
*/
class ActualTask {
ActualTask() {
//Fake a long task,
//making a random amount of progress every second.
while (!canceled && !done) {
try {
Thread.sleep(1000); //sleep for a second
current += Math.random() * 100; //make some progress
if (current >= lengthOfTask) {
done = true;
current = lengthOfTask;
}
statMessage = "Completed " + current +
" out of " + lengthOfTask + ".";
} catch (InterruptedException e) {
System.out.println("ActualTask interrupted");
}
}
}
}
}
/**
* This is the 3rd version of SwingWorker (also known as
* SwingWorker 3), an abstract class that you subclass to
* perform GUI-related work in a dedicated thread. For
* instructions on and examples of using this class, see:
*
* http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html
*
* Note that the API changed slightly in the 3rd version:
* You must now invoke start() on the SwingWorker after
* creating it.
*/
abstract class SwingWorker {
private Object value; // see getValue(), setValue()
/**
* Class to maintain reference to current worker thread
* under separate synchronization control.
*/
private static class ThreadVar {
private Thread thread;
ThreadVar(Thread t) { thread = t; }
synchronized Thread get() { return thread; }
synchronized void clear() { thread = null; }
}
private ThreadVar threadVar;
/**
* Get the value produced by the worker thread, or null if it
* hasn't been constructed yet.
*/
protected synchronized Object getValue() {
return value;
}
/**
* Set the value produced by worker thread
*/
private synchronized void setValue(Object x) {
value = x;
}
/**
* Compute the value to be returned by the <code>get</code> method.
*/
public abstract Object construct();
/**
* Called on the event dispatching thread (not on the worker thread)
* after the <code>construct</code> method has returned.
*/
public void finished() {
}
/**
* A new method that interrupts the worker thread. Call this method
* to force the worker to stop what it's doing.
*/
public void interrupt() {
Thread t = threadVar.get();
if (t != null) {
t.interrupt();
}
threadVar.clear();
}
/**
* Return the value created by the <code>construct</code> method.
* Returns null if either the constructing thread or the current
* thread was interrupted before a value was produced.
*
* @return the value created by the <code>construct</code> method
*/
public Object get() {
while (true) {
Thread t = threadVar.get();
if (t == null) {
return getValue();
}
try {
t.join();
}
catch (InterruptedException e) {
Thread.currentThread().interrupt(); // propagate
return null;
}
}
}
/**
* Start a thread that will call the <code>construct</code> method
* and then exit.
*/
public SwingWorker() {
final Runnable doFinished = new Runnable() {
public void run() { finished(); }
};
Runnable doConstruct = new Runnable() {
public void run() {
try {
setValue(construct());
}
finally {
threadVar.clear();
}
SwingUtilities.invokeLater(doFinished);
}
};
Thread t = new Thread(doConstruct);
threadVar = new ThreadVar(t);
}
/**
* Start the worker thread.
*/
public void start() {
Thread t = threadVar.get();
if (t != null) {
t.start();
}
}
}
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