[SOLVED] ListBox out of bounds

[trev]

I have a listbox which is filled with items. If I clear the items, I get a "List index (-1) out of bounds" error only if an item has been selected. So I tried unsetting ItemIndex but no joy.

Code: Pascal  [Select][+][-]

1.   picListBox.ClearSelection;
2.   picListBox.ItemIndex := -1;
3.   ShowMessage('1');
4.   picListBox.Items.Clear;
5.   ShowMessage('2');  
6.  

Ideas?

[skalogryz]

please try r61760 (the problem seemed to be with TListBox not clearing selections)

BUT,. if it doesn't work, please provide a sample. I couldn't replicate the issue on a standalone project. (With TListBox and TButton calling for ListBox1.Clear).

[trev]

The out of bounds error has moved

Code: Pascal  [Select][+][-]

1.   ShowMessage('1');
2.   picListBox.ClearSelection;
3.   ShowMessage('ItemIndex = ' + IntToStr(picListBox.ItemIndex));
4.   picListBox.Items.Clear;
5.  

It used to occur at picListBox.Items.Clear but with r61769 it now occurs at picListBox.ClearSelection which does now clear the selection.

Error dialog attached.

I'll work on a minimal demo.

[trev]

I'm having trouble replicating it in a standalone app.

In the real app if I comment out the picListBox.ClearSelection the error still occurs at picListBox.Items.Clear and if I comment that out it occurs at picListBox.Items.Assign(List).

If there is no highlighted selection, then the error does not occur.

I'll keep trying to replicate in a standalone app or resort to deconstructing the real app.

[skalogryz]

I think I know what's going on.

on you ListBox you've OnSelectionChanged event.

The event is NOT fired when you do ListBox.Items.Clear on Windows.
The event IS fired when you do the same on macOS.

It's likely you're trying to access an item by .ItemIndex. which is -1 at this point. And this is how you're getting the message.

upd: please try trunk

[trev]

Yep r61775 fixes the Out of Bounds error :-)

Thanks Dmitry.