AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Occasional exceptions in event dispatching          AppletTalk.com Forum Index -> Java GUI Toolkits View previous topic :: View next topic   Author Message aspa Guest Posted: Mon Apr 18, 2005 7:44 pm    Post subject: Occasional exceptions in event dispatching hi i'm having some problems with a Java applet i've written using Java2 v1.3. the applet is a JApplet and uses JTree component to view a tree hierarchy for the user. occasionally, i see the below error message on Java console (Mac OS X v10.3.9, Safari, Java 1.4.2_05-141.4). this error seems to be related to switching focus between the browser and other applications. any clue on what might be causing this? apple.awt.EventQueueExceptionHandler Caught Throwable : java.lang.IllegalArgumentException: null source java.lang.IllegalArgumentException: null source at java.util.EventObject.<init>(EventObject.java:34) at java.awt.AWTEvent.<init>(AWTEvent.java:226) at java.awt.event.ComponentEvent.<init>(ComponentEvent.java:94) at java.awt.event.WindowEvent.<init>(WindowEvent.java:174) at java.awt.event.WindowEvent.<init>(WindowEvent.java:211) at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:576) at java.awt.Component.dispatchEventImpl(Component.java:3572) at java.awt.Container.dispatchEventImpl(Container.java:1671) at java.awt.Window.dispatchEventImpl(Window.java:1606) at java.awt.Component.dispatchEvent(Component.java:3543) at java.awt.EventQueue.dispatchEvent(EventQueue.java:456) at java.awt.SentEvent.dispatch(SentEvent.java:50) at java.awt.DefaultKeyboardFocusManager$DefaultKeyboardFocusManagerSentEvent.dispatch(DefaultKeyboardFocusManager.java:145) at java.awt.EventQueue.dispatchEvent(EventQueue.java:454) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:234) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:178) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:170) at java.awt.EventDispatchThread.run(EventDispatchThread.java:100) br. aspa Back to top Nigel Wade Guest Posted: Tue Apr 19, 2005 2:15 pm    Post subject: Re: Occasional exceptions in event dispatching aspa wrote: Quote: hi i'm having some problems with a Java applet i've written using Java2 v1.3. the applet is a JApplet and uses JTree component to view a tree hierarchy for the user. occasionally, i see the below error message on Java console (Mac OS X v10.3.9, Safari, Java 1.4.2_05-141.4). this error seems to be related to switching focus between the browser and other applications. any clue on what might be causing this? apple.awt.EventQueueExceptionHandler Caught Throwable : java.lang.IllegalArgumentException: null source java.lang.IllegalArgumentException: null source at java.util.EventObject.<init>(EventObject.java:34) at java.awt.AWTEvent.<init>(AWTEvent.java:226) at java.awt.event.ComponentEvent.<init>(ComponentEvent.java:94) at java.awt.event.WindowEvent.<init>(WindowEvent.java:174) at java.awt.event.WindowEvent.<init>(WindowEvent.java:211) at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:576) at java.awt.Component.dispatchEventImpl(Component.java:3572) at java.awt.Container.dispatchEventImpl(Container.java:1671) at java.awt.Window.dispatchEventImpl(Window.java:1606) at java.awt.Component.dispatchEvent(Component.java:3543) at java.awt.EventQueue.dispatchEvent(EventQueue.java:456) at java.awt.SentEvent.dispatch(SentEvent.java:50) at java.awt.DefaultKeyboardFocusManager$DefaultKeyboardFocusManagerSentEvent.dispatch(DefaultKeyboardFocusManager.java:145) at java.awt.EventQueue.dispatchEvent(EventQueue.java:454) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:234) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:178) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:170) at java.awt.EventDispatchThread.run(EventDispatchThread.java:100) br. aspa Are you following Sun's guidelines and creating the GUI in the event dispatching thread: http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html#EDT If you create the GUI in the main thread, and somehow realize a component in that thread which you then go on to modify it's possible that you will be attempting to modify it before it's been fully realized by the EDT. This can have very unpredictable results, including inexplicable null pointer exceptions. It creates a race condition; sometimes it will work, sometimes it will fail. -- Nigel Wade, System Administrator, Space Plasma Physics Group, University of Leicester, Leicester, LE1 7RH, UK E-mail : [email]nmw (AT) ion (DOT) le.ac.uk[/email] Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555 Back to top aspa Guest Posted: Sat Apr 23, 2005 6:12 pm    Post subject: Re: Occasional exceptions in event dispatching Nigel Wade wrote: Quote: aspa wrote: Are you following Sun's guidelines and creating the GUI in the event dispatching thread: http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html#EDT If you create the GUI in the main thread, and somehow realize a component in that thread which you then go on to modify it's possible that you will be attempting to modify it before it's been fully realized by the EDT. This can have very unpredictable results, including inexplicable null pointer exceptions. It creates a race condition; sometimes it will work, sometimes it will fail. thanks for the tip. i re-read the guidelines. i was modifying the model in edt but the gui was being created in main thread. now, i populate the model in main but after that create the gui in edt. let's see if this helps. br. aspa Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AppletTalk.com Forum Index -> Java GUI Toolkits All times are GMT Page 1 of 1   Jump to: Select a forum Java Newsgroups----------------Java DiscussionsWeb-based java games comp.lang.java 3D Graphics API's for Java Java: Support and criticism Java System Announcements comp.lang.java.api JavaBeans Java and CORBA Java and Databases comp.lang.java.developer Java GUI Toolkits Java Help comp.lang.java.javascript JVM, native methods and hardware comp.lang.java.misc Java Language Programming Security and Java comp.lang.java.setup Java Software Tools comp.lang.java.tech ibm.software.java.linux  Non-English Java Newsgroups----------------Java Language (German)Language Java (Français)Java (Italian)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.