/*
* #!
* Ontopia Vizigator
* #-
* Copyright (C) 2001 - 2013 The Ontopia Project
* #-
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* !#
*/
package net.ontopia.topicmaps.viz;
import javax.swing.SwingUtilities;
/**
* 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.
*/
public abstract class SwingWorker {
Object value; // see getValue(), setValue()
/**
* Class to maintain reference to current worker thread under separate
* synchronization control.
*/
static class ThreadVar {
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();
}
}
}