After more fully evaluating the problem, the simple test case that I wrote DOES exhibit the behavior when I follow all requisite steps:
1) Load the flash 2) Sort by the only field The sorting appears to be necessary. It seems to me, from watching, that when the first row moves off of the screen, the viewport moves to keep the old first row to be the first row in the viewport. After that, that particular row is no longer followed, but it will jump subsequent times, perhaps to try and follow the new first-row, when it moves away from being the first row? Either way, with sorting on this example using all native Flex components jumps around like crazy. <?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"; layout="absolute" applicationComplete="appComplete();"> <mx:DataGrid dataProvider="{ac}" width="100%" height="100%"> <mx:columns> <mx:DataGridColumn headerText="Testing" dataField="timer" /> </mx:columns> </mx:DataGrid> <mx:Script> <![CDATA[ import mx.utils.ObjectProxy; import mx.collections.ArrayCollection; import flash.utils.Timer; import mx.core.Application; public var t: Timer = new Timer(1000); [Bindable] public var ac: ArrayCollection = new ArrayCollection([ new ObjectProxy({'name': 'Test 1', 'timer': 0}), new ObjectProxy({'name': 'Test 1', 'timer': 0}), new ObjectProxy({'name': 'Test 1', 'timer': 0}), new ObjectProxy({'name': 'Test 1', 'timer': 0}), new ObjectProxy({'name': 'Test 1', 'timer': 0}), // Repeat enough times to make this take up more than one screen... or just shrink your window new ObjectProxy({'name': 'Test 1', 'timer': 0}), new ObjectProxy({'name': 'Test 1', 'timer': 0})]); private function appComplete(): void { this.t.addEventListener("timer", this.doTick); this.t.start(); } private function doTick(e: Event): void { for (var i: Number = 0; i < Application.application.ac.length; i++) { Application.application.ac.getItemAt(i).timer += ( Math.random() * 10) - 5; } } ]]> </mx:Script> </mx:Application> Daniel On 4/5/07, Daniel Grace <[EMAIL PROTECTED]> wrote:
Just to repay the quick reply to my email, you should know that a very quck test case failed to replicate the bug without the rest of my framework involved. I have also noticed a few more things about this bug. First, it only happens if I have a sorted field (I don't do any custom sorting, and it happens at least with String sorting, which is the most common field anyone sorts on in this application) and it mostly happens when the text I am sorting on has changed somewhere (unfortunately, that's common enough that I can't be sure that's part of the true cause). I don't have lines selected at the time. I created a function to try and find the bug (in a DataGrid subclass): public function set veriticalScrollPosition(n: Number): void { Application.application.logError("Setting scroll position to " + n); super.verticalScrollPosition = n; } Note that this failed to ever run, even when I saw the bug happen. Are there any other functions that could trap when this bug is rearing its head? I like having the source to most/all of the framework for when something like this happens, but there sure is a lot of code to try and understand. Daniel On 4/5/07, Alex Harui <[EMAIL PROTECTED]> wrote: > > I don't remember any bugs like that. Can you build a small test case > that uses regular DataGrid? > > ------------------------------ > *From:* [email protected] [mailto:[EMAIL PROTECTED] *On > Behalf Of *Daniel Grace > *Sent:* Thursday, April 05, 2007 12:40 PM > *To:* [email protected] > *Subject:* [flexcoders] DataGrid Jumping > > I am using a DataGrid that is mostly stock (overrode drawRowBackground > and set dataProvider. This particular datagrid has a lot of > information in it that changes every second. That's all fine. > > If there is a vertical scroll bar (common) and I am scrolled to the > top, with no rows selected, it will periodically jump down to what > appears to be roughly the halfway point. This seems to happen when > something changes (and happened a lot less frequently before I put the > timers in). There is a chance that I have messed something up, but I > doubt it. I know that it happened before I overrode set dataProvider. > > My real question is -- is this addressed in the hotfix? I don't see > specific mentioning of it on > http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=kb401224 , > though there are fixes in the datagrid. After seeing a few problem > reports here I'm not overly eager to install the hotfix if it is not > going to fix a problem that I am having (also, the page referenced > suggests this strategy). > > Or, does anyone know what might be causing my scroll position to jump, > without overriding any functions that would logically cause such a > behavior? > > Daniel> >
