With useVirtualLayout set to true the list will create a set number of renderers. As you scroll the list will recycle these item renderers. In this scenario you are never guaranteed that the renderer associated with your data will remain with that data.
If you want to guarantee that the renderer always remains connected with the data item then set useVirtualLayout to false. Alex can correct me, but you may also be able to check if the data is the same data in the set data override and if so prevent setting the super.data property. Although, I think once it is decided a renderer will be recycled the data property is set to null before hand. On Mon, Aug 9, 2010 at 4:26 AM, Florian <[email protected]> wrote: > > > My thoughts more specifically: > - the data property is set -> an invalidation should occur. > - a renderer is reused -> an invalidation should occur. > - a renderer is scrolled within the view port -> no invalidation should > occur, after its size is determined. > > Or am i wrong? > > > --- In [email protected] <flexcoders%40yahoogroups.com>, > "Florian" <florian.saliho...@...> wrote: > > > > Yes, i understand this aspect of the component model. But since nothing > happens after the renderer references a new "data", why is there the > invalidation of renderers which have a correct state already? > > > > --- In [email protected] <flexcoders%40yahoogroups.com>, Alex > Harui <aharui@> wrote: > > > > > > When useVirtualLayout=true, renderers are being recycled so more > invalidation does go on. It pretty much has to. You might be able to block > some of it, depending on your scenario. > > > > > > > > > On 8/9/10 12:12 AM, "Florian" <florian.salihovic@> wrote: > > > > > > > > > > > > > > > > > > > > > When scrolling my custom item renderer, which inherits from > ItemRenderer, i notice significant performance problems, when scrolling the > list. It seems like the list's layout is invalidating the component when the > list is scrolled. > > > > > > I configured the list's layout with the following parameters: > > > > > > <s:VerticalLayout gap="0" horizontalAlign="contentJustify" > paddingBottom="0" paddingLeft="0" paddingRight="0" paddingTop="0" > rowHeight="82" useVirtualLayout="true", variableRowHeight="false" /> > > > > > > I also overwrote the renderer's measuredWidth and measuredHeight > properties: > > > > > > override public function set measuredHeight(value:Number):void > > > { > > > height = super.measuredHeight = value; > > > } > > > > > > override public function set measuredWidth(value:Number):void > > > { > > > width = super.measuredWidth = value; > > > } > > > > > > The question for me now popping up is, how to avoid those unnecessary > invalidation cycles? I'd expect the layout to be at least as smart as > handling size changes only when the item renderer's owner changes it's > width, since the rowHeight is set. > > > > > > Best regards > > > > > > > > > > > > > > > > > > > > > -- > > > Alex Harui > > > Flex SDK Team > > > Adobe System, Inc. > > > http://blogs.adobe.com/aharui > > > > > > > >
