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java.lang.ClassCastException: com/ms/wfc/app/Timer$TimerProc from a Window.callback

Does anybody know what kind of windows callbacks throws the following exception (see the callstack below).
The callstack contains a ListView.wndProc call, so it's possible that it's a ListView specific question.
The application was built with Microsoft Visual J++ 6.0.

java.lang.ClassCastException: com/ms/wfc/app/Timer$TimerProc
            at com/ms/wfc/app/Window.fromHandle
            at com/ms/wfc/ui/Control.fromHandle
            at com/ms/wfc/ui/Control.reflectMessage
            at com/ms/wfc/ui/Control.wmNotify
            at com/ms/wfc/ui/Control.wndProc
            at com/ms/wfc/ui/Form.wndProc
            at com/ms/wfc/app/Application$ParkingForm.wndProc
            at com/ms/wfc/ui/Control$ControlWindow.wndProc
            at com/ms/wfc/app/Window.callback
            at com/ms/wfc/win32/Windows.CallWindowProc
            at com/ms/wfc/app/Window.defWndProc
            at com/ms/wfc/ui/Control$ControlWindow.defWndProc
            at com/ms/wfc/ui/Control.defWndProc
            at com/ms/wfc/ui/Control.wmPaint
            at com/ms/wfc/ui/Control.wndProc
            at com/ms/wfc/ui/ListView.wndProc
            at com/ms/wfc/ui/Control$ControlWindow.wndProc
            at com/ms/wfc/app/Window.callback
            at com/ms/wfc/win32/Windows.DispatchMessage
            at com/ms/wfc/app/Application$ThreadContext.runMessageLoop
            at com/ms/wfc/app/Application.run
            at Form2.main

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Kevin Cross

Please show snippet of code associated to this error message if it told you or if your main() method is fairly small just paste in the whole thing.

java.lang.ClassCastException ==> Usually occurs when you are setting one object equal to another object and the explicit or implicit casting cannot be done. Examples would be you can cast a sub class to a parent class, but not the other way around. Things of that nature.

Usually you will see this in code as:
Type2 t2 = (Type2) t1;

Kev

tctdev

ASKER

mwvisa1:
I can't reproduce the problem, it's very ad hoc. My source is not too little (~2 MB) and the main() method is very simple (see below)

I think the conflict must be between the followings:
- Timer (I use ~30 timer, but I use these very rarely, the most is disabled)
- com.ms.wfc.app.MethodInvoker: to make changes on the Controls requested from a thread (not from the main thread)
- ListView callback (it appears on the callstack lista)

I know the ClassCastException but it's thrown by an automatic windows callback, not by my code. I never use the
Timer.TimerProc class, and I never cast it.

jkr:
I think this problem is closer to mfc than standard java programming (because of microsoft java using and windows callbacks)

I hope, that somebody met something like similar.
Thanks!

	public static void main(String args[])
	{
		Form2.params = args;
		Application.OLERequired();
		Application.run(new Form2());
	}

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Kevin Cross

This could be a threading issue which is why it happens haphazardly as it depends on occurrence of conflict.

// this statement makes me think you are setting a static variable
// what happens if another call comes in and changes this mid stream
// is params defined as String[] like args is
Form2.params = args; 
 
Application.OLERequired();
 
// you then call a new form instance here
// hopefully this form uses the static params passed in above
Application.run(new Form2());
 
 
/********************/
// could this work for you
Form2 f = new Form2(); // or Form2(args); 
f.params = args;
Application.OLERequired();
Application.run(f);

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tctdev

ASKER

The Form2 object is created only in the main(), has only one instance.
I don't know what another call could come in, but I'm going to give it a try.

I will inform you within few days.

Thanx.

tctdev

ASKER

Not work. The exception and the callstack are the same.

SOLUTION

Kevin Cross

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tctdev

ASKER

I'll remove all the timers ... Come back soon ...