/*
* Jitsi, the OpenSource Java VoIP and Instant Messaging client.
*
* Distributable under LGPL license.
* See terms of license at gnu.org.
*
* Based on 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 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.
*/
package net.java.sip.communicator.util.swing;
import java.lang.Thread.*;
import javax.swing.SwingUtilities;
/**
* Utility class based on the javax.swing.SwingWorker. <tt>SwingWorker</tt> is
* an abstract class that you subclass to perform GUI-related work in a
* dedicated thread. In addition to the original SwingWorker this class takes
* care of exceptions occured during the execution of the separate thread. It
* would call a catchException() method in the Swing thread if an exception
* occurs.
*
* @author Yana Stamcheva
*/
public 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()
throws Exception;
/**
* Called on the event dispatching thread (not on the worker thread)
* after the <code>construct</code> method has returned.
*/
public void finished()
{
}
/**
* Called on the event dispatching thread (not on the worker thread)
* if an exception has occured during the <code>construct</code> method.
*
* @param exception the exception that has occured
*/
public void catchException(Throwable exception)
{
}
/**
* 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());
}
catch (final Exception exception)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
catchException(exception);
}
});
}
finally
{
threadVar.clear();
}
SwingUtilities.invokeLater(doFinished);
}
};
Thread t = new Thread(doConstruct);
t.setUncaughtExceptionHandler(new SwingUncaughtExceptionHandler());
threadVar = new ThreadVar(t);
}
/**
* Start the worker thread.
*/
public void start()
{
Thread t = threadVar.get();
if (t != null)
{
t.start();
}
}
/**
* An exception handler that calls the catchException() in the Swing thread
* if an exception occurs while processing the construct method in a
* separate thread.
*/
private class SwingUncaughtExceptionHandler
implements UncaughtExceptionHandler
{
public void uncaughtException(Thread t, final Throwable e)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
catchException(e);
}
});
}
}
}