How to prevent/cancel an item to change in a TListBox?

Question

With FireMonkey and several items in a TListBox...

I'd like to be able to allow/cancel an item change...

Like we can do it with the TListView's event: OnChanging

The events OnMouseDown & OnKeyDown are triggered before the change (item values are still for the current/old selected item, not for the new selection)...

So I can stored easill stored the current ListBox ItemIndex... and after the change, move back to it.. but this is just awful, dirty, ...

Anyway to do it nicely?

Mike Sutton Mike Sutton · Accepted Answer · 2012-11-12T07:34:12

Your probably best off creating a custom component to add the functionality by overriding the SetItemIndex method:

type TCustomListBox = class(TListBox)
  protected
    procedure SetItemIndex(Value: Integer);override;
  end;

procedure Register;

...

procedure Register;
begin
  RegisterControls('Custom', [TCustomListBox]);
end;

procedure TCustomListBox.SetItemIndex(Value: Integer); 
begin
  if <condition> then
inherited
end;

initialization
  RegisterFMXClasses([TCustomListBox]);
end;

You can, of course, add an event for the conditional.

How to prevent/cancel an item to change in a TListBox?

1 Answers