Flex AdvancedDataGrid deactivate lazy rendering

Question

i have a AdvancedDataGrid coponent with some custom Rows. I have a limited number of rows visible within the component. The other rows can be accessed via a scrollbar. Within my application i have ha Save & Next Button which saves the actual selected record and iterates the Grid's selected item by 1 until the end. Unfortunately this procedure works only until i reach the end of the visible rows. After that the Grid crashes when i select the not visible row and try to scroll there programatically:

//Bad Crash
this.documentBrowser.dg.selectedIndex = index + 1;
this.documentBrowser.dg.validateNow();
this.documentBrowser.dg.scrollToIndex(this.dg.selectedIndex);

I found out that the next element isn't instanciated in that moment. Is there any possibility to render all items in the grid after loading or to deactivate the lazy rendering?

The stack trace:

TypeError: Error #1010: A term is undefined and has no properties. at mx.controls.listClasses::AdvancedListBase/makeRowsAndColumnsWithExtraRows()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/advancedgrids/src/mx/controls/listClasses/AdvancedListBase.as:4008] at mx.controls.listClasses::AdvancedListBase/updateDisplayList()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/advancedgrids/src/mx/controls/listClasses/AdvancedListBase.as:3582] at mx.controls::AdvancedDataGridBaseEx/updateDisplayList()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/advancedgrids/src/mx/controls/AdvancedDataGridBaseEx.as:2033] at mx.controls::AdvancedDataGrid/updateDisplayList()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/advancedgrids/src/mx/controls/AdvancedDataGrid.as:2907] at mx.controls.listClasses::AdvancedListBase/validateDisplayList()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/advancedgrids/src/mx/controls/listClasses/AdvancedListBase.as:3480] at mx.managers::LayoutManager/validateDisplayList()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/framework/src/mx/managers/LayoutManager.as:744] at mx.managers::LayoutManager/doPhasedInstantiation()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/framework/src/mx/managers/LayoutManager.as:827] at mx.managers::LayoutManager/doPhasedInstantiationCallback()[/Users/justinmclean/Documents/ApacheFlexSDK/frameworks/projects/framework/src/mx/managers/LayoutManager.as:1195]

If you run in the debug player, it should give you a stack trace. Post the stack trace will help you get closer to the source of the problem — flexicious.com, May 28 '13 at 20:54
Hello, i did that and it only shows that the scrollToIndexFunction lasts more than 15 seconds. With that information i debugged the ADG and found out that there are not all Elements within the backing list of the ADG rendered. When i scroll the ADG to the not rendered Item the error happens. That's why i asked about the lazy rendering feature of the ADG. — Andreas, May 29 '13 at 06:41

pseudopeach · Accepted Answer · 2013-05-30T15:20:19.667

I'm pretty sure that lazy rendering feature re-uses your item renderers as soon as the roll off the screen (to optimize performance). So maybe you only need to do whatever you're doing to the visible ones and it will remain 'done' to all renderer instances?

Are you sure you need to access the ACTUAL visible rows themselves and not the items in your dataProvider that back them? If accessing your backing data is okay, maybe you should iterate through your dataProvider instead.

I made this little application that scrolls to and highlights a row with a function called gotoGridItem(index). I scroll to the item before trying to set the selectedIndex--maybe that was what gave you the crash?

Here's my code:

<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
               xmlns:s="library://ns.adobe.com/flex/spark" 
               xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">

    <mx:AdvancedDataGrid id="theGrid" dataProvider="{rowDataItems}" x="50" y="50"/>
    <s:NumericStepper id="rowIndSpr" minimum="0" maximum="{theGrid.dataProvider.length-1}" value="{8}"/>
    <s:Button click="gotoGridItem(int(rowIndSpr.value))" label="Go" y="20" />

    <fx:Script>
        <![CDATA[
            import mx.collections.ArrayCollection;
            [bindable] public var rowDataItems:ArrayCollection = new ArrayCollection([

                //...lots of data items for rows ...

            ]);

            public function gotoGridItem(index:uint):void{


                theGrid.scrollToIndex(index);
                theGrid.selectedIndex = index;
                theGrid.validateNow();
            }
        ]]>

    </fx:Script>
</s:Application>

Hello, good point. But since i want to use the scrollToIndex function i have to set the selectedIndex. — Andreas, May 30 '13 at 08:14
Yes, that code does help. SO IMPORTANT NOTE HERE. 1. scrollToIndex 2. set selectedIndex only if the item is visible after scrolling. Thank you for clarification — Andreas, May 31 '13 at 07:37
Yeah, maybe it finishes instantiating the renderers after it scrolls to them. — pseudopeach, May 31 '13 at 20:14

Flex AdvancedDataGrid deactivate lazy rendering

1 Answers1