Exception in markForRedraw

[marco_fuellemann]

hi,
we have a large smartgwt-application using smart-gwt-5.0-2015-01-06 with gwt-2.6.1 on IE11.

In the logfile we see the following exception, which looks to me like a Nullpointer-Exception in the markForRedraw-method.

Do you know this issue, or do you know which element/object or what might be null?
Do you know if this exception occurs, in a method where we explicitly call "markForRedraw", or could it also be that smartGwt calls somehow "markForRedraw".

We call "markForRedraw" on several ListGrids and Canvas. But I could not find the cause.

com.google.gwt.event.shared.UmbrellaException: Exception caught: (TypeError) 
 description: Die Eigenschaft "last" eines undefinierten oder Nullverweises kann nicht abgerufen werden.
 number: -2146823281
 stack: TypeError: Die Eigenschaft "last" eines undefinierten oder Nullverweises kann nicht abgerufen werden.
   at isc_c_Class__getLastProto (https://xxxxxxxxxxxxxxxxxxxx/sc/modules/ISC_Core.js:258:148)
   at isc_c_Class_Super (https://xxxxxxxxxxxxxxxxxxxx/sc/modules/ISC_Core.js:249:112)
   at isc_Layout_markForRedraw (https://xxxxxxxxxxxxxxxxxxxx/sc/modules/ISC_Foundation.js:235:410)
   at AKc (https://xxxxxxxxxxxxxxxxxxxx/yyyyyyyyyyyyyyyyyy.cache.html:4114:30)
   at vzd (https://xxxxxxxxxxxxxxxxxxxx/yyyyyyyyyyyyyyyyyy.cache.html:8835:9180)
   at jZ (https://xxxxxxxxxxxxxxxxxxxx/yyyyyyyyyyyyyyyyyy.cache.html:8817:2861)
   at AZ (https://xxxxxxxxxxxxxxxxxxxx/yyyyyyyyyyyyyyyyyy.cache.html:8393:186)
   at oZ (https://xxxxxxxxxxxxxxxxxxxx/yyyyyyyyyyyyyyyyyy.cache.html:7827:59)
   at IAd (https://xxxxxxxxxxxxxxxxxxxx/yyyyyyyyyyyyyyyyyy.cache.html:8835:11093)
   at kZ (https://xxxxxxxxxxxxxxxxxxxx/yyyyyyyyyyyyyyyyyy.cache.html:4398:43)
 __gwt$exception: <skipped>: Die Eigenschaft "last" eines undefinierten oder Nullverweises kann nicht abgerufen werden.
	at Unknown.LN(Unknown Source)
	at Unknown.SN(Unknown Source)
	at Unknown.OZ(Unknown Source)
	at Unknown.RZ(Unknown Source)

Regards, Marco

[Isomorphic]

This does indicate that your code is calling markForRedraw() - it's not an internal framework call.

This isn't much information to go on (it would help if you could at least translate the German exception message), but one possible way to have markForRedraw() fail would be if you called it on a widget that had been destroy()d already, which is invalid.

[marco_fuellemann]

The exception translates to something like: "The property "last" of an undefined or null reference can not be retrieved".
I assume that the method markForRedraw() uses internally the property "last" and that results in a nullpointer-exception.

With your answer I could already cleanup some calls to markForRedraw(), thank you.

[Isomorphic]

It's not markForRedraw() that calls last(), but something that markForRedraw() calls: our internal mechanism for doing superclass calls in JavaScript.

As far as how that call could end up hitting a null, our best guess is still that an API is being called on a destroy()d widget, or similarly, that a widget is being destroy()d when it is still in the midst of handling an event; both kinds of calls would be invalid usage.

If you can isolate a runnable test case where this error occurs even though your usage appears to be valid, we can take a look.

[marco_fuellemann]

Ok, I changed the code to:

        if (isVisible() && getDestroying() != Boolean.TRUE && getDestroyed() != Boolean.TRUE) {
            markForRedraw();
        }

But I still get the same "The property "last" of an undefined or null reference can not be retrieved"-exception (this time with more details):

Caused by: com.google.gwt.core.client.JavaScriptException: (TypeError) : Die Eigenschaft "last" eines undefinierten oder Nullverweises kann nicht abgerufen werden.
	at Unknown.qW(StackTraceCreator.java:180)
	at Unknown.NN(StackTraceCreator.java:518)
	at Unknown.QN(Throwable.java:51)
	at Unknown.SN(RuntimeException.java:25)
	at Unknown.bV(JavaScriptException.java:117)
	at Unknown.X0b(Exceptions.java:45)
	at Unknown.Z0b(Exceptions.java:29)
	at Unknown.zKc(ListGrid.java:16109)
	at Unknown.kzd(NavigationTreeGrid.java:96)
	at Unknown.vzd(NavigationTreeGrid.java:89)
	at Unknown.hZ(ValueChangeEvent.java:127)
	at Unknown.yZ(SimpleEventBus.java:194)
	at Unknown.mZ(HandlerManager.java:127)

Do you have an idea what might cause this?

[HumTum]

Admin plzzz give a answer on last question




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[Isomorphic]

Unfortunately, not much we can do here. It appears that your app is in some invalid state when markForRedraw runs, but there's no way we can theorize as to the cause without a way to reproduce the problem. It is very likely to be an application level issue of some sort rather than a framework bug.

Your best bet is probably to attempt to isolate the problem in your app, simplifying the functionality until you can determine how you get into this bad state.
Most likely this will reveal some invalid usage, but if it doesn't and you think there's a framework bug here, we would then need to see a simple runnable standalone test case demonstrating the problem to comment further.

Regards
Isomorphic Software