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Removing a Model Element causes Invalid thread access [message #533186]

Wed, 12 May 2010 10:08

Chris
Messages: 44
Registered: April 2010

Member

Hi,

currently I'm developing an UML class editor for Eclipse. When the user drags a Java-File (ICompilationUnit) onto the drawing area, the contained Java type (IType) it is rendered as UML type box. Now my problem is the following:

When the .java-file is deleted, the diagram's EditPart (implementing the IElementChangedListener interface), informs the diagram's model about this deletion via method call.
Then the model looks if it containes any UML boxes of types contained in that deleted file.
If any such a model of a UML box exists, it removes the model of the box from itself and informs the diagram's EditPart about the deletion via method call using a PropertyChangeSupport delegate.
The diagram's EditPart then calls refreshChildren(); which ultimately results in an "Invalid thread access" in
org.eclipse.draw2d.DeferredUpdateManager.sendUpdateRequest(D eferredUpdateManager.java:243).

Is it not permissible to let EditPart and ModelClass interact in the way I let them via method calls? How can I avoid the "Invalid thread access"?

Any insight you can give would be highly appreciated.
Regards,
Chris

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Re: Removing a Model Element causes Invalid thread access [message #533493 is a reply to message #533186]

Fri, 14 May 2010 05:15

Vijay Raj
Messages: 604
Registered: July 2009

Senior Member

replace your refreshChildren method code like this

refreshChildren()
{
Display.getDefault().syncExec(new runnable()
            {
                          //Method code
            }
}

This is not required usually because the delete happens from ui only, but in your case the java file file has been deleted and that notification is non UI thread.

---------------------
why, mr. Anderson, why, why do you persist?
Because I Choose To.
Regards,
Vijay

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Re: Removing a Model Element causes Invalid thread access [message #533794 is a reply to message #533493]

Mon, 17 May 2010 02:33

Chris
Messages: 44
Registered: April 2010

Member

Hi,

I wanted to thank you, your tip set me on the right track for the final solution of the problem.

With a bit of modification, your tip worked just fine. I did not override the refreshChildren method in my EditPart, so I wrapped its only occurence in propertyChange. That helped a bit. I still got the exception, but the MVC got all updated correctly and the editor would no longer freeze.

The next step was a good long look at the stack trace. Looking at it, I decided, the best place to catch the exception would be in the firePropertyChange method. So I created a nested class FirePropertyChangeRunnable implementing the Runnable interface and accepting the three arguments of firePropertyChange in the constructor.

Now, any time my model would call firePropertyChange , it calls

Display.getDefault().syncExec(new FirePropertyChangeRunnable(CHILD_REMOVED_PROPERTY, null, child));

instead.

So thanks again, you made my day Smile

Regards,
Chris

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