Author: Tomas Rutkauskas

How to sort a TCheckListBox without loosing the check state

Answer:

Sorting without loosing the check state is a bit of a challenge, but it can be 
done. The code below has only been superficially tested:

1   { ... }
2   type
3     TItemState = class
4     public
5       Data: TObject;
6       Checked: Boolean;
7       constructor Create(aData: TObject; aChecked: Boolean);
8     end;
9   
10  constructor TItemState.Create(aData: TObject; aChecked: Boolean);
11  begin
12    inherited Create;
13    Data := aData;
14    Checked := aChecked;
15  end;
16  
17  procedure CustomSortChecklist(aList: TChecklistbox; Compare: TStringListSortCompare 
18  = nil);
19  var
20    sl: TStringlist;
21    i: Integer;
22    stateobj: TItemState;
23  begin
24    Assert(Assigned(aList), 'CustomSortChecklist: no list to sort.');
25    sl := TStringlist.Create;
26    try
27      sl.Assign(aList.Items);
28      for i := 0 to sl.Count - 1 do
29        sl.Objects[i] := TItemState.Create(sl.Objects[i], aList.Checked[i]);
30      if Assigned(Compare) then
31        sl.CustomSort(Compare)
32      else
33        sl.Sort;
34      alist.Items.BeginUpdate;
35      try
36        aList.Clear;
37        for i := 0 to sl.Count - 1 do
38        begin
39          stateobj := sl.Objects[i] as TItemState;
40          aList.Items.AddObject(sl[i], stateobj.Data);
41          aList.Checked[i] := stateobj.Checked;
42        end;
43      finally
44        aList.Items.EndUpdate;
45      end;
46    finally
47      for i := 0 to sl.Count - 1 do
48        if Assigned(sl.Objects[i]) and (sl.Objects[i] is TItemState) then
49          sl.Objects[i].Free;
50      sl.free;
51    end;
52  end;
53  
54  procedure TForm1.Button1Click(Sender: TObject);
55  begin
56    CustomSortChecklist(checklistbox1);
57  end;
58  
59  function ReverseSort(List: TStringList; Index1, Index2: Integer): Integer;
60  begin
61    result := AnsiCompareText(list[index2], list[index1]);
62  end;
63  
64  procedure TForm1.Button2Click(Sender: TObject);
65  begin
66    CustomSortChecklist(checklistbox1, Reversesort);
67  end;