svn-gvsig-desktop / trunk / org.gvsig.desktop / org.gvsig.desktop.library / org.gvsig.utils / src / main / java / org / gvsig / utils / swing / threads / SwingWorker.java @ 40561
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/**
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* gvSIG. Desktop Geographic Information System.
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*
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* Copyright (C) 2007-2013 gvSIG Association.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 3
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301, USA.
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*
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* For any additional information, do not hesitate to contact us
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* at info AT gvsig.com, or visit our website www.gvsig.com.
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*/
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package org.gvsig.utils.swing.threads; |
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import javax.swing.SwingUtilities; |
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/**
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* This is the 3rd version of SwingWorker (also known as
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* SwingWorker 3), an abstract class that you subclass to
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* perform GUI-related work in a dedicated thread. For
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* instructions on and examples of using this class, see:
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*
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* http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html
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*
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* Note that the API changed slightly in the 3rd version:
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* You must now invoke start() on the SwingWorker after
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* creating it.
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*/
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public abstract class SwingWorker { |
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private Object value; // see getValue(), setValue() |
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/**
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* Class to maintain reference to current worker thread
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* under separate synchronization control.
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*/
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private static class ThreadVar { |
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private Thread thread; |
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ThreadVar(Thread t) { thread = t; }
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synchronized Thread get() { return thread; } |
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synchronized void clear() { thread = null; } |
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} |
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private ThreadVar threadVar;
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/**
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* Get the value produced by the worker thread, or null if it
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* hasn't been constructed yet.
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*/
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protected synchronized Object getValue() { |
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return value;
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} |
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/**
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* Set the value produced by worker thread
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*/
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private synchronized void setValue(Object x) { |
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value = x; |
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} |
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/**
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* Compute the value to be returned by the <code>get</code> method.
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*/
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public abstract Object construct(); |
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/**
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* Called on the event dispatching thread (not on the worker thread)
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* after the <code>construct</code> method has returned.
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*/
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public void finished() { |
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} |
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/**
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* A new method that interrupts the worker thread. Call this method
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* to force the worker to stop what it's doing.
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*/
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public void interrupt() { |
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Thread t = threadVar.get();
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if (t != null) { |
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t.interrupt(); |
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} |
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threadVar.clear(); |
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} |
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/**
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* Return the value created by the <code>construct</code> method.
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* Returns null if either the constructing thread or the current
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* thread was interrupted before a value was produced.
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*
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* @return the value created by the <code>construct</code> method
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*/
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public Object get() { |
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while (true) { |
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Thread t = threadVar.get();
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if (t == null) { |
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return getValue();
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} |
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try {
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t.join(); |
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} |
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catch (InterruptedException e) { |
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Thread.currentThread().interrupt(); // propagate |
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return null; |
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} |
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} |
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} |
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/**
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* Start a thread that will call the <code>construct</code> method
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* and then exit.
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*/
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public SwingWorker() {
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final Runnable doFinished = new Runnable() { |
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public void run() { finished(); } |
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}; |
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Runnable doConstruct = new Runnable() { |
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public void run() { |
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try {
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setValue(construct()); |
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} |
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finally {
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threadVar.clear(); |
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} |
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SwingUtilities.invokeLater(doFinished);
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} |
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}; |
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Thread t = new Thread(doConstruct); |
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threadVar = new ThreadVar(t);
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} |
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/**
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* Start the worker thread.
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*/
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public void start() { |
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Thread t = threadVar.get();
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if (t != null) { |
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t.start(); |
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} |
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} |
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} |
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