EDU.oswego.cs.dl.util.concurrent.misc
Class SwingWorker
- Runnable
public abstract class SwingWorker
implements Runnable
An abstract class that you subclass to perform GUI-related work
in a dedicated thread.
This class was adapted from the SwingWorker written by Hans Muller
and presented in "Using a Swing Worker Thread" in the Swing Connection
- http://java.sun.com/products/jfc/tsc/articles/threads/threads2.html
A closely related version of this class is described in
"The Last Word in Swing Threads" in the Swing Connection
- http://java.sun.com/products/jfc/tsc/articles/threads/threads3.html
This SwingWorker is a ThreadFactoryUser and implements Runnable. The
default thread factory creates low-priority worker threads. A special
constructor is provided for enabling a timeout. When the timeout
expires, the worker thread is interrupted.
Note: Using a timeout of
Long.MAX_VALUE
will not impose a
timeout but will create an additional thread of control that will respond
to an interrupt even if the
construct
implementation ignores
them.
Sample Usage
import EDU.oswego.cs.dl.util.concurrent.TimeoutException;
import EDU.oswego.cs.dl.util.concurrent.misc.SwingWorker;
public class SwingWorkerDemo extends javax.swing.JApplet {
private static final int TIMEOUT = 5000; // 5 seconds
private javax.swing.JLabel status;
private javax.swing.JButton start;
private SwingWorker worker;
public SwingWorkerDemo() {
status = new javax.swing.JLabel("Ready");
status.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
getContentPane().add(status, java.awt.BorderLayout.CENTER);
start = new javax.swing.JButton("Start");
getContentPane().add(start, java.awt.BorderLayout.SOUTH);
start.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
if (start.getText().equals("Start")) {
start.setText("Stop");
status.setText("Working...");
worker = new DemoSwingWorker(TIMEOUT);
worker.start();
} else {
worker.interrupt();
}
}
});
}
private class DemoSwingWorker extends SwingWorker {
private static final java.util.Random RAND = new java.util.Random();
public DemoSwingWorker(long msecs) {
super(msecs);
}
protected Object construct() throws InterruptedException {
// Take a random nap. If we oversleep, the worker times out.
Thread.sleep(RAND.nextInt(2*TIMEOUT));
return "Success";
}
protected void finished() {
start.setText("Start");
try {
Object result = get();
status.setText((String) result);
}
catch (java.lang.reflect.InvocationTargetException e) {
Throwable ex = e.getTargetException();
if (ex instanceof TimeoutException) {
status.setText("Timed out.");
} else if (ex instanceof InterruptedException) {
status.setText("Interrupted.");
} else {
status.setText("Exception: " + ex);
}
}
catch (InterruptedException ex) {
// event-dispatch thread won't be interrupted
throw new IllegalStateException(ex+"");
}
}
}
}
Version:
- Joseph Bowbeer
- Hans Muller
SwingWorker() - Creates new SwingWorker with no timeout.
|
SwingWorker(ThreadFactory factory, long msecs) - Creates new SwingWorker with specified thread factory and timeout.
|
SwingWorker(long msecs) - Creates new SwingWorker with specified timeout.
|
protected Object | construct() - Computes the value to be returned by the
get method.
|
protected void | finished() - Called on the event dispatching thread (not on the worker thread)
after the
construct method has returned.
|
Object | get() - Return the value created by the
construct method,
waiting if necessary until it is ready.
|
InvocationTargetException | getException() - Get the exception, or null if there isn't one (yet).
|
long | getTimeout() - Returns timeout period in milliseconds.
|
void | interrupt() - Stops the worker and sets the exception to InterruptedException.
|
boolean | isReady() - Return whether the
get method is ready to
return a value.
|
void | run() - Calls the
construct method to compute the result,
and then invokes the finished method on the event
dispatch thread.
|
void | start() - Starts the worker thread.
|
Object | timedGet(long msecs) - Wait at most msecs to access the constructed result.
|
SwingWorker
public SwingWorker()
Creates new SwingWorker with no timeout.
SwingWorker
protected SwingWorker(ThreadFactory factory,
long msecs)
Creates new SwingWorker with specified thread factory and timeout.
factory
- factory for worker threads.msecs
- timeout in milliseconds, or 0
for no time limit.
SwingWorker
public SwingWorker(long msecs)
Creates new SwingWorker with specified timeout.
msecs
- timeout in milliseconds, or 0
for no time limit.
construct
protected Object construct()
throws Exception
Computes the value to be returned by the get
method.
finished
protected void finished()
Called on the event dispatching thread (not on the worker thread)
after the construct
method has returned.
get
public Object get()
throws InterruptedException,
InvocationTargetException
Return the value created by the construct
method,
waiting if necessary until it is ready.
- the value created by the
construct
method
getException
public InvocationTargetException getException()
Get the exception, or null if there isn't one (yet).
This does not wait until the worker is ready, so should
ordinarily only be called if you know it is.
- the exception encountered by the
construct
method wrapped in an InvocationTargetException
getTimeout
public long getTimeout()
Returns timeout period in milliseconds. Timeout is the
maximum time to wait for worker to complete. There is
no time limit if timeout is 0
(default).
interrupt
public void interrupt()
Stops the worker and sets the exception to InterruptedException.
isReady
public boolean isReady()
Return whether the get
method is ready to
return a value.
- true if a value or exception has been set. else false
run
public void run()
Calls the construct
method to compute the result,
and then invokes the finished
method on the event
dispatch thread.
start
public void start()
Starts the worker thread.
timedGet
public Object timedGet(long msecs)
throws TimeoutException,
InterruptedException,
InvocationTargetException
Wait at most msecs to access the constructed result.
- current value
TimeoutException
- if not ready after msecs