Author: Tomas Rutkauskas
My TListView is populated with file names in the first column and their sizes in
the second column. To sort the data in the columns I use certain code. Now I would
like the second column sorted not by Ansi values, where 822 is greater than 1000,
but by numerical values. The second column must behave like the first, which means
that the first click sorts the values ascending and the next click sorts them
descending. Can anyone help me?
Answer:
Start a new project, and drop a ListView on the form. Replace all of the unit's
code with code listed below. Set the ListView1's OnColumnClick Event to point to
the ListView1ColumnClick in the code and link the form's OnCreate to the
FormCreate. Run the program. Every time you click on the "Column 2" header, the
column will sort in the opposite order. Note, if you click too quick, it'll be
considered a double click, and it's not set up for that. Also, if you click on
Column 1's header, it'll sort alphabetically.
1 unit Unit1;
2
3 {$O-}
4
5 interface
6
7 uses
8 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
9 ComCtrls,
10 StdCtrls;
11
12 type
13 TForm1 = class(TForm)
14 ListView1: TListView;
15 procedure FormCreate(Sender: TObject);
16 procedure ListView1ColumnClick(Sender: TObject; Column: TListColumn);
17 private
18 NameSortOrder, SizeSortOrder: integer;
19 public
20 end;
21
22 var
23 Form1: TForm1;
24
25 implementation
26
27 {$R *.DFM}
28
29 procedure TForm1.FormCreate(Sender: TObject);
30 var
31 i: Integer;
32 ListItem: TListItem;
33 begin
34 Randomize;
35 NameSortOrder := -1;
36 SizeSortOrder := -1;
37 with ListView1 do
38 begin
39 Align := alClient;
40 ViewStyle := vsReport;
41 with Columns.Add do
42 begin
43 Caption := 'Column 1';
44 width := 90;
45 end;
46 with Columns.Add do
47 begin
48 Caption := 'Column 2';
49 width := 90;
50 Alignment := taRightJustify;
51 end;
52 for i := 1 to 20 do
53 begin
54 ListItem := ListView1.Items.Add;
55 with ListItem do
56 begin
57 caption := format('FileName %2d', [i]);
58 SubItems.add(Format('%3.6n', [random]));
59 end;
60 end;
61 end;
62 end;
63
64 function SizeCustomSort(Item1, Item2: TListItem; ParamSort: integer): integer;
65 stdcall;
66 var
67 R1, R2: real;
68 code: Integer;
69 begin
70 val(Item1.SubItems.Strings[0], R1, code); {ignore code}
71 val(Item2.SubItems.Strings[0], R2, code);
72 if R1 > R2 then
73 result := ParamSort
74 else if R1 < R2 then
75 result := -ParamSort
76 else
77 result := 0;
78 end;
79
80 procedure TForm1.ListView1ColumnClick(Sender: TObject; Column: TListColumn);
81 begin
82 if Column.Index = 1 then
83 begin
84 ListView1.CustomSort(@SizeCustomSort, SizeSortOrder);
85 SizeSortOrder := SizeSortOrder * -1; {reverse the next sort order}
86 end
87 else
88 begin
89 ListView1.SortType := stText;
90 ListView1.AlphaSort;
91 end;
92 end;
93
94 end.
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