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From "Roger L. Whitcomb" <Roger.Whitc...@actian.com>
Subject RE: 2.0.1 release and threads
Date Mon, 16 Jan 2012 20:34:03 GMT
But note that while this would eliminate the exception thrown by this “assert” it will
not eliminate the subtle bugs that are really there because your UI updates are not being
done in the event thread.  So, even though things appear to work, there really are problems
that will end up biting you at some point.  That was the reason for putting in this assert,
to alert you to the fact that there are really problems that you are not aware of.

 

~Roger

 

From: Andrei Pozolotin [mailto:andrei.pozolotin@gmail.com] 
Sent: Monday, January 16, 2012 12:31 PM
To: dev@pivot.apache.org
Cc: Roger L. Whitcomb; user@pivot.apache.org
Subject: Re: 2.0.1 release and threads

 

Lukas:

you can provide a temporary work around 
by providing an alternative implementation to thread checker used by assert

org.apache.pivot.wtk.Container.assertEventDispatchThread

Andrei

-------- Original Message  --------
Subject: Re: 2.0.1 release and threads
From: Roger L. Whitcomb <Roger.Whitcomb@actian.com> <mailto:Roger.Whitcomb@actian.com>

To: dev@pivot.apache.org, user@pivot.apache.org
Date: Mon 16 Jan 2012 12:39:29 PM CST



Hi Lukas,
        That approach is still valid (and encouraged) EXCEPT that all updates to the UI MUST
happen in the Event Dispatch Thread (or 'EDT').  This is now enforced in 2.0.1 (as you can
see).  This is inherent, not only in Pivot, but all other GUI frameworks (that I know of).
 So, even though it "appeared" to work fine with 2.0, there are/were subtle problems that
you just didn't see yet.
        What you need to do is use either a TaskAdapter class or call the ApplicationContext.queueCallback()
method to schedule your UI updates in the EDT, rather than doing them directly in the background
thread.  For an example you can look at the Tutorial here: http://pivot.apache.org/tutorials/background-tasks.html.
 I can step you through your code in more detail if you need more help.  Our application also
has a number of places where we have needed to do this.
        I'm going to transfer this to the User list since this is not a developer issue, per
se, since it is not a bug.  It is, however, something that has definitely changed (for the
better) in 2.0.1.
        Thank you for using Pivot, though!!
 
~Roger
 
-----Original Message-----
From: Lukáš Macháček [mailto:cgrim@coolmail.cz] 
Sent: Monday, January 16, 2012 8:17 AM
To: dev@pivot.apache.org
Subject: 2.0.1 release and threads
 
Hi all,
 
I am now testing coming 2.0.1 release of Pivot libraries with my desktop 
application developed during previous year on Pivot 2.0 and am facing 
one great problem with threads :-(
 
Every task which loads data at background and worked in 2.0 well now 
throws exception like this:
 
java.lang.IllegalStateException: this method can only be called from the 
AWT event dispatch thread, and not from "Thread-26"
     at org.apache.pivot.wtk.Container$1.check(Container.java:872)
     at 
org.apache.pivot.wtk.Container.assertEventDispatchThread(Container.java:880)
     at org.apache.pivot.wtk.Component.repaint(Component.java:2047)
     at org.apache.pivot.wtk.Component.repaint(Component.java:1998)
     at 
org.apache.pivot.wtk.skin.ComponentSkin.repaintComponent(ComponentSkin.java:351)
     at 
org.apache.pivot.wtk.skin.ComponentSkin.repaintComponent(ComponentSkin.java:346)
     at 
org.apache.pivot.wtk.skin.terra.TerraTableViewSkin.enabledChanged(TerraTableViewSkin.java:1394)
     at 
org.apache.pivot.wtk.Component$ComponentStateListenerList.enabledChanged(Component.java:399)
     at org.apache.pivot.wtk.Component.setEnabled(Component.java:2173)
     at cz.cgrim.alchemist.dql.RunQueryTask.execute(RunQueryTask.java:58)
     at cz.cgrim.alchemist.dql.RunQueryTask.execute(RunQueryTask.java:23)
     at 
org.apache.pivot.util.concurrent.Task$ExecuteCallback.run(Task.java:42)
     at 
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
     at java.util.concurrent.FutureTask.run(FutureTask.java:166)
     at java.lang.Thread.run(Thread.java:722)
 
In this example at first it disables TableView (to disable user 
interaction during background load of data), than it loaded results from 
DQL query into that TableView and at the end it enabled that TableView.
 
I have tens of use cases with similar approach in my application used to 
load data at background because it can take long time to finish while 
user can work on another tasks.
 
Another equal problem with thread has occurred for example in my custom 
Log4J Appender:
 
Exception in thread "Timer-2" java.lang.IllegalStateException: this 
method can only be called from the AWT event dispatch thread, and not 
from "Timer-2"
     at org.apache.pivot.wtk.Container$1.check(Container.java:872)
     at 
org.apache.pivot.wtk.Container.assertEventDispatchThread(Container.java:880)
     at org.apache.pivot.wtk.Component.invalidate(Component.java:1955)
     at 
org.apache.pivot.wtk.skin.ComponentSkin.invalidateComponent(ComponentSkin.java:340)
     at 
org.apache.pivot.wtk.skin.TextAreaSkinParagraphView.textRemoved(TextAreaSkinParagraphView.java:419)
     at 
org.apache.pivot.wtk.TextArea$Paragraph$ParagraphListenerList.textRemoved(TextArea.java:55)
     at 
org.apache.pivot.wtk.TextArea$Paragraph.removeText(TextArea.java:153)
     at org.apache.pivot.wtk.TextArea.insertText(TextArea.java:757)
     at org.apache.pivot.wtk.TextArea.insertText(TextArea.java:730)
     at 
cz.cgrim.alchemist.logger.TextAreaAppender.append(TextAreaAppender.java:41)
     at 
org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
     at 
org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:66)
     at org.apache.log4j.Category.callAppenders(Category.java:206)
     at org.apache.log4j.Category.forcedLog(Category.java:391)
     at org.apache.log4j.Category.log(Category.java:856)
     at com.documentum.fc.common.DfLogger.warn(DfLogger.java:151)
     at 
com.documentum.fc.client.impl.bof.cache.ClassCacheManager$CacheCleanupTask.run(ClassCacheManager.java:602)
     at java.util.TimerThread.mainLoop(Timer.java:555)
     at java.util.TimerThread.run(Timer.java:505)
 
Here I simply implement AppenderSkeleton and append every line from 
LoggingEvent into Pivot's TextPane. Log4J runs it in separate thread.
 
Please, is now there another approach how to use threads and Pivot's 
Task to do changes in GUI or is it a bug? In 2.0 release everything 
spoken here worked like a charm.
 
Thanks for an advance.
Lukas Machacek

 

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