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

That's exactly the type of idea I needed - it made me look at the DataGroup (inside of the false stack) and voila - the problem was in a Spark List I am also using inside of the application! (it would probably be enough to read the originial post - well, silly me)

Now I know precisely when the error happens:

<s:List labelFunction="formatSelected" dataProvider="{dp.selected}" />

This is the list, and as you could guess, "dp" is an object, that changes with the controlling of the TabBar.

1) If I set dp to null and prior to that, didn't change dp.selected from its initial new ArrayCollection(), then the error wasn't thrown.

2) If I set dp to null, and prior to that, did add some objects to the ArrayCollection, everything was still fine.

3) But if set dp to null, and prior to that changed the ArrayCollection and as the last step called ArrayCollection.removeAll(), then the error did occur.

Now, I have a feeling that the problem might be inside of the binding mechanism of MXML (which by the way doesn't work as expected:

<info:MultipleLinesBox showedArray="{dp.selected}"> -> triggers only with a change to "dp" or assignment to "dp.selected", but not when you add or remove items - as it doest with Spark List's 'dataProvider' - another question of mine )

Two interesting facts are:

1) setting useVirtualLayout="false" on the Spark List does solve the problem

2) if so, in a situation where the error occured previously, now the list "shrinks" to almost 0 height (the border stays, probably)

I won't be probably using the List at all in the final product (another 'by the way': the fact that I have to go and search for and in the ListSkin.mxml file to change the number of List's required rows properly in my application still seems ridiculous to me - but that's Flex4's skins in all their beauty ) but I am still interested in the whereabouts of this error...

As I stated above:

1) setting useVirtualLayout="false" on the Spark List does solve the problem

You might want to try it first (unless you need VirtualLayout to be 'true').

Thank you!

I will try to set useVirtualLayout to false and check if it helps.

I'm having the exact same problem now so I'll be watching this thread. Just discovered it. I see in a question above it is asked if we're removing the item from the dataProvider of the list or the source arrayCollection (I'm doing the latter). Setting useVirtualLayout = "false" doesn't help.

Did you ever get this fixed?

I'm managing to reproduce it 18 months later....

Latest Flex SDK and latest Air SDK. Practically the same issue you're having. It occurs for me when I call a removeAll() on the array collection that is bound as the data provider for a spark list.