Flex 4 - Error with DataGrid in Module

Question

Hey, I'm using Flex 4 final and am now getting the following error when loading a Module with a DataGrid inside:
TypeError: Error #1009: Cannot access a property or method of a null object reference
    at mx.styles::StyleProtoChain$/initProtoChainForUIComponentStyleName()[E:\dev\4.0.0\framewor ks\projects\framework\src\mx\styles\StyleProtoChain.as:356]
It is created via MXML:
<mx:Module layout="absolute" xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:mx="library://ns.adobe.com/flex/mx">
    <mx:DataGrid>
        ... config etc.
    </mx:DataGrid>
    ... other code
</mx:Module>
If I remove the DataGrid the Module works fine. The code used to work in the various betas.
If I put a DataGrid in the main application that also renders fine, so it's only inside Modules.
Thanks in advance for any help or ideas!

Answer 1

Hi Darrell,
     I have the exact same error, and yes I am using module.factory.create() but I get an error when I try to add the module to my stage.  Here it is the code in my modReady function.
var _sd:Object = new Object();         
_sd = util.app.SDModule.factory.create() as SequenceDetail;
            _sd.sequenceId = event.currentTarget.selectedItem.sequenceId;
            _sd.environment = event.currentTarget.selectedItem.environment;
            _sd.seqname = event.currentTarget.selectedItem.sequenceName;
            util.app.page.addChildAt(_sd as SequenceDetail, util.app.page.numChildren);
            util.app.nav_buttons.selectedIndex = -1;
            util.app.page.selectedIndex = util.app.page.numChildren-1;
I get an error on util.app.page.addChildAt(........).
error is
TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at mx.styles::StyleProtoChain$/initProtoChainForUIComponentStyleName()[E:\dev\4.0.0\framewor ks\projects\framework\src\mx\styles\StyleProtoChain.as:356]
    at mx.styles::StyleProtoChain$/initProtoChain()[E:\dev\4.0.0\frameworks\projects\framework\s rc\mx\styles\StyleProtoChain.as:171]
    at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::initProtoChain()[E:\dev\4.0.0\frameworks\proje cts\framework\src\mx\core\UIComponent.as:10186]
    at mx.core::UIComponent/regenerateStyleCache()[E:\dev\4.0.0\frameworks\projects\framework\sr c\mx\core\UIComponent.as:10249]
    at mx.core::Container/regenerateStyleCache()[E:\dev\4.0.0\frameworks\projects\framework\src\ mx\core\Container.as:3737]
    at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::addingChild()[E:\dev\4.0.0\frameworks\projects \framework\src\mx\core\UIComponent.as:7114]
    at mx.core::Container/http://www.adobe.com/2006/flex/mx/internal::rawChildren_addChild()[E:\dev\4.0.0\frameworks \projects\framework\src\mx\core\Container.as:4464]
    at mx.core::ContainerRawChildrenList/addChild()[E:\dev\4.0.0\frameworks\projects\framework\s rc\mx\core\ContainerRawChildrenList.as:143]
    at mx.containers::TabNavigator/createChildren()[E:\dev\4.0.0\frameworks\projects\framework\s rc\mx\containers\TabNavigator.as:559]
    at mx.core::UIComponent/initialize()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\ UIComponent.as:7250]
    at mx.core::Container/initialize()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\Co ntainer.as:3129]
    at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\4.0.0\frameworks\projects\ framework\src\mx\core\UIComponent.as:7142]
    at mx.core::Container/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\4.0.0\frameworks\projects\ framework\src\mx\core\Container.as:3951]
    at mx.core::Container/addChildAt()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\Co ntainer.as:2616]
    at mx.core::Container/addChild()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\Cont ainer.as:2534]
    at mx.core::Container/createComponentFromDescriptor()[E:\dev\4.0.0\frameworks\projects\frame work\src\mx\core\Container.as:4371]
    at mx.core::Container/createComponentsFromDescriptors()[E:\dev\4.0.0\frameworks\projects\fra mework\src\mx\core\Container.as:4160]
    at mx.containers::Panel/createComponentsFromDescriptors()[E:\dev\4.0.0\frameworks\projects\f ramework\src\mx\containers\Panel.as:1685]
    at mx.core::Container/createChildren()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\cor e\Container.as:3187]
    at mx.containers::Panel/createChildren()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\c ontainers\Panel.as:1198]
    at mx.core::UIComponent/initialize()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\ UIComponent.as:7250]
    at mx.core::Container/initialize()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\Co ntainer.as:3129]
    at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\4.0.0\frameworks\projects\ framework\src\mx\core\UIComponent.as:7142]
    at mx.core::Container/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\4.0.0\frameworks\projects\ framework\src\mx\core\Container.as:3951]
    at mx.core::Container/addChildAt()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\Co ntainer.as:2616]
    at mx.core::Container/addChild()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\Cont ainer.as:2534]
    at mx.core::Container/createComponentFromDescriptor()[E:\dev\4.0.0\frameworks\projects\frame work\src\mx\core\Container.as:4371]
    at mx.core::Container/createComponentsFromDescriptors()[E:\dev\4.0.0\frameworks\projects\fra mework\src\mx\core\Container.as:4160]
    at mx.core::Container/createChildren()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\cor e\Container.as:3187]
    at mx.core::UIComponent/initialize()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\ UIComponent.as:7250]
    at mx.core::Container/initialize()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\Co ntainer.as:3129]
    at SequenceDetail/initialize()
    at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\4.0.0\frameworks\projects\ framework\src\mx\core\UIComponent.as:7142]
    at mx.core::Container/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\4.0.0\frameworks\projects\ framework\src\mx\core\Container.as:3951]
    at mx.core::Container/addChildAt()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\Co ntainer.as:2616]
    at mx.containers::ViewStack/addChildAt()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\c ontainers\ViewStack.as:1426]
    at com::MyDBResult/displaySequenceDetail()[/Users/jbhavsar/Documents/workspace/virome/src/co m/MyDBResult.as:114]
    at <anonymous>()[/Users/jbhavsar/Documents/workspace/virome/src/com/MyDBResult.as:103]
    at flash.events::EventDispatcher/dispatchEventFunction()
    at flash.events::EventDispatcher/dispatchEvent()
    at ModuleInfoProxy/moduleEventHandler()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\mo dules\ModuleManager.as:1168]
    at flash.events::EventDispatcher/dispatchEventFunction()
    at flash.events::EventDispatcher/dispatchEvent()
    at ModuleInfo/readyHandler()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\modules\Modul eManager.as:812]
    at flash.events::EventDispatcher/dispatchEventFunction()
    at flash.events::EventDispatcher/dispatchEvent()
    at mx.core::FlexModuleFactory/update()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\cor e\FlexModuleFactory.as:433]
    at mx.core::FlexModuleFactory/docFrameHandler()[E:\dev\4.0.0\frameworks\projects\framework\s rc\mx\core\FlexModuleFactory.as:582]
    at mx.core::FlexModuleFactory/docFrameListener()[E:\dev\4.0.0\frameworks\projects\framework\ src\mx\core\FlexModuleFactory.as:126]
Thanks
Jay
p.s: Please dont hammer me if my code isn't upto standard, I am learning this as I go along.