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Original Reporter info from Mantis: Martin @martin_frb

• Reporter name: Martin Friebe

Description:

See the code below. It throws an exception "index 1 out of bounds" on the 2nd delete.

The reason is FCacheIndex = 1 / lcl\include\listitems.inc line 280

procedure TListItems.ItemDestroying(const AItem: TListItem);
var
  idx: Integer;
begin
  // Don't use IndexOf, it updates the cache, which then will become invalid
  //DebugLn('TListItems.ItemDestroying ',dbgs(AItem));
  if  (FCacheIndex <> -1) and (FCacheItem = AItem) then
    idx := FCacheIndex
  else
    idx := FItems.IndexOf(AItem);

This line sets FCacheIndex
Item := ListView.Items[1];

Delete does not explicitly reset FCacheIndex, but obviously the cached item is no longer at index=1

If the listview has a handle, then it is reset here (lcl\include\customlistview.inc 265):

procedure TCustomListView.CNNotify(var AMessage: TLMNotify);
..
    LVN_DELETEITEM: begin
      Item := FListItems[nm^.iItem];

But clearly it is not save to rely on this.

This is also the cause for #22541 (closed)

Additional information:

procedure TForm1.Button1Click(Sender: TObject);
var
  Item: TListItem;
  ListView: TListView;
begin
  ListView := TListView.Create(self);

  Item := ListView.Items.Add;
  Item := ListView.Items.Add;
  Item := ListView.Items[1];

  ListView.Items.Delete(0);
  ListView.Items.Delete(0);
end;

Mantis conversion info:

• Mantis ID: 22552
• Version: 1.1 (SVN)
• Fixed in revision: 38145 (#25658113)