List Error:invalidIndex when remove an item

Question

Hi Guys,
I got the following exception, when i removed an item from spark list. I stepped into to see the index, i looked all right. Somehow, it went the following stack, and the index became an invalid index, which i am not sure where it was from. I found this thread - http://forums.adobe.com/thread/692482?tstart=0, but it is not the same problem.
Error: invalidIndex
    at spark.layouts.supportClasses::LinearLayoutVector/remove()[E:\dev\4.x\frameworks\projects\ spark\src\spark\layouts\supportClasses\LinearLayoutVector.as:541]
    at spark.layouts::VerticalLayout/elementRemoved()[E:\dev\4.x\frameworks\projects\spark\src\s park\layouts\VerticalLayout.as:1311]
    at spark.components::DataGroup/http://www.adobe.com/2006/flex/mx/internal::itemRemoved()[E:\dev\4.x\frameworks\projects\s park\src\spark\components\DataGroup.as:1580]
    at spark.components::DataGroup/removeRendererAt()[E:\dev\4.x\frameworks\projects\spark\src\s park\components\DataGroup.as:625]
    at spark.components::DataGroup/removeAllItemRenderers()[E:\dev\4.x\frameworks\projects\spark \src\spark\components\DataGroup.as:656]
    at spark.components::DataGroup/createItemRenderers()[E:\dev\4.x\frameworks\projects\spark\sr c\spark\components\DataGroup.as:840]
    at spark.components::DataGroup/commitProperties()[E:\dev\4.x\frameworks\projects\spark\src\s park\components\DataGroup.as:899]
    at mx.core::UIComponent/validateProperties()[E:\dev\4.x\frameworks\projects\framework\src\mx \core\UIComponent.as:7933]
    at mx.managers::LayoutManager/validateProperties()[E:\dev\4.x\frameworks\projects\framework\ src\mx\managers\LayoutManager.as:572]
    at mx.managers::LayoutManager/doPhasedInstantiation()[E:\dev\4.x\frameworks\projects\framewo rk\src\mx\managers\LayoutManager.as:730]
    at mx.managers::LayoutManager/doPhasedInstantiationCallback()[E:\dev\4.x\frameworks\projects \framework\src\mx\managers\LayoutManager.as:1072]
Thanks in advance,
Cheng

Answer 1

Hi,
I have exactly the same problem, getting the same error message and stack report (precisely the same).
All I can say about the error is that it is very random - I can't figure out what changes the situation to produce the error.
I have a class, extending the spark's TabBar, with a function to close a tab:
public class VerticalIconTabBar extends TabBar
         public function closeTab(closedTab:int, selectedTab:int):void {
             if (dataProvider.length == 0) return;
             if (dataProvider is ViewStack){
                 //remove the entire child from the dataProvider, which also removes it from the ViewStack
                 (dataProvider as ViewStack).removeChildAt(closedTab);
             //adjust selectedIndex appropriately
             if (dataProvider.length == 0) {
                 selectedIndex = -1;
             } else if (closedTab < selectedTab) {
                 selectedIndex = selectedTab - 1;
             } else if (closedTab == selectedTab) {
                 selectedIndex = (selectedTab == 0 ? 0 : selectedTab - 1);
             } else {
                 selectedIndex = selectedTab;
I am showing you the whole  function, though I believe that the '//adjust selectedIndex  appropriately' part is not behind the problem. The problem occurs,  though, only when I am removing the last element from the taskbar (as far as I can tell) and it happens after this function has been called.
One thing I noticed, but it might be sort of a red herring, is that I can reproduce the error after working a little bit longer (20+ seconds lets say) in the particular Viewstack view - or it's not about time but rather about clicking on different buttons in my UI, I am simply guessing.
These are the locals of the LinearLayoutVector and its remove(index:uint) function at the time of the error thrown:
this: pendingInserts = null, pendingRemoves = null, pendingLength = -1, length = 0
local:
index = 0 (this causes the error as it equals this.length)
lastIndex = 0
intervalStart = 0
I suppose the length shouldn't be 0 or the function shouldn't be called at all - but I cannot affect that.
I would be very grateful if you could point me towards the direction for solving this, as it causes the whole UI to jam and the only solution is to restart the whole application.
Thank you,
xixixao