[FLEX-34022] Null object reference when setting columns on Spark DataGrid

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Not A Problem
• Affects Version/s: Apache Flex 4.9.0, Apache Flex 4.11.0
• Component/s: Spark: DataGrid
• Environment: Mac OS X
• Assignee: Justin Mclean
• Reporter: Curtis J. Aube
• Created: 03/Jan/14 18:35
• Updated: 03/Jan/14 22:44
• Resolved: 03/Jan/14 22:43

Description

If you set a bindable columns property for the DataGrid before it is initialized and set an itemRenderer for one of the columns, you get a null object reference when the DataGrid is initialized.

Here is an example:
<?xml version="1.0" encoding="utf-8"?>
<s:Application creationComplete="creationComplete()" minHeight="600" minWidth="955" preinitialize="setColumns()" xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:mx="library://ns.adobe.com/flex/mx"
xmlns:s="library://ns.adobe.com/flex/spark">
<fx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
import mx.collections.ArrayList;
import spark.components.gridClasses.GridColumn;
import spark.skins.spark.DefaultItemRenderer;

[Bindable]
private var columns:ArrayList;
[Bindable]
private var dp:ArrayCollection;

private function creationComplete():void
{
var myHistoryItems:Array = new Array;
myHistoryItems.push(

{filename: "Testing"}

);
dp = new ArrayCollection(myHistoryItems);
}

private function setColumns():void

{ var column:GridColumn var myColumns:ArrayList = new ArrayList; column = new GridColumn("filename"); column.headerText = "Filename"; column.itemRenderer = new ClassFactory(DefaultItemRenderer); myColumns.addItem(column); columns = myColumns; }

]]>
</fx:Script>
<s:DataGrid height="100%" width="100%" columns="

{columns}

" dataProvider="

{dp}

"/>
</s:Application>

Here is the stack trace:
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at spark.components::Group/addElement()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/spark/src/spark/components/Group.as:1395]
at spark.components.gridClasses::GridLayout/createTypicalItemRenderer()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/spark/src/spark/components/gridClasses/GridLayout.as:756]
at spark.components.gridClasses::GridLayout/updateTypicalCellSizes()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/spark/src/spark/components/gridClasses/GridLayout.as:891]
at spark.components.gridClasses::GridLayout/measure()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/spark/src/spark/components/gridClasses/GridLayout.as:452]
at spark.components.supportClasses::GroupBase/measure()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/spark/src/spark/components/supportClasses/GroupBase.as:1156]
at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::measureSizes()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/framework/src/mx/core/UIComponent.as:8514]
at mx.core::UIComponent/validateSize()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/framework/src/mx/core/UIComponent.as:8438]
at spark.components::Group/validateSize()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/spark/src/spark/components/Group.as:1065]
at mx.managers::LayoutManager/validateSize()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/framework/src/mx/managers/LayoutManager.as:673]
at mx.managers::LayoutManager/doPhasedInstantiation()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/framework/src/mx/managers/LayoutManager.as:800]
at mx.managers::LayoutManager/doPhasedInstantiationCallback()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/framework/src/mx/managers/LayoutManager.as:1188]