Solved

Sorting a Virtual Listview

Posted on 2007-11-20
6
1,973 Views
Last Modified: 2012-08-13
Hi,
I asked a question sometime ago (http://www.experts-exchange.com/Programming/Languages/Pascal/Delphi/Q_21718319.html?sfQueryTermInfo=1+listview+virtual) and would liek some addtional help.

In the solution given in the link above - I am left with MyList. This virtual list is displayed in a listview. Can somebody show me how to sort this now when I click on one of the three column headers.

I would appreciate some working code if possible.
0
Comment
Question by:Romans
  • 3
  • 3
6 Comments
 
LVL 14

Expert Comment

by:SteveBay
ID: 20323762
You need to sort your list and then redisplay the contents.
This code fragment is not complete but has the principal parts.
Let me know if you need more detail.

Steve
function SortWord(Item1,Item2 : pointer) : integer;
begin
 result := CompareText( TOccurrence(Item1).TheWord, TOccurrence(Item2).TheWord);
end;
 
function SortCount(Item1,Item2 : pointer) : integer;
begin
 result := TOccurrence(Item2).Count - TOccurrence(Item1).Count;
end;
 
function SortFirstPos(Item1,Item2 : pointer) : integer;
begin
 result := TOccurrence(Item2).FirstPos - TOccurrence(Item1).FirstPos;
end;
 
procedure TForm1.ListView1ColumnClick(Sender: TObject;    Column: TListColumn);
begin
	if Column.Index = 0 then
		MyList.Sort(SortWord)
	else if Column.Index = 1 then
		MyList.Sort(SortCount)
	else if Column.Index = 2 then
		MyList.Sort( SortFirstPos);
 
	// Refresh ListView Display.
end;

Open in new window

0
 
LVL 14

Accepted Solution

by:
SteveBay earned 500 total points
ID: 20323897
Here is the complete working Unit. I made a minor mistake in the number sort routines.
It sould be Item1 - Item2 not Item2 - Item1

Steve
unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ComCtrls, Contnrs;
type
  TOccurrence = class
    TheWord: string;
    Count: integer;
    FirstPos: integer;
  end;
 
type
  TForm1 = class(TForm)
    ListView1: TListView;
    procedure ListView1ColumnClick(Sender: TObject; Column: TListColumn);
    procedure FormShow(Sender: TObject);
    procedure ListView1Data(Sender: TObject; Item: TListItem);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
	MyList : TObjectList;
 
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
function SortWord(Item1,Item2 : pointer) : integer;
begin
	result := CompareText( TOccurrence(Item1).TheWord, TOccurrence(Item2).TheWord);
end;
 
function SortCount(Item1,Item2 : pointer) : integer;
begin
	result := TOccurrence(Item1).Count - TOccurrence(Item2).Count;
end;
 
function SortFirstPos(Item1,Item2 : pointer) : integer;
begin
	result := TOccurrence(Item1).FirstPos - TOccurrence(Item2).FirstPos;
end;
 
 
 
procedure TForm1.ListView1ColumnClick(Sender: TObject;    Column: TListColumn);
begin
	if Column.Index = 0 then
		MyList.Sort(SortWord)
	else if Column.Index = 1 then
		MyList.Sort(SortCount)
	else if Column.Index = 2 then
		MyList.Sort( SortFirstPos);
 
	ListView1.Refresh;
end;
 
procedure TForm1.FormShow(Sender: TObject);
var oc  : TOccurrence;
begin
	MyList := TObjectList.Create;
 
	oc := TOccurrence.Create;
	oc.TheWord := 'The';
	oc.Count := 2;
	oc.FirstPos := 0;
	MyList.Add(oc);
 
	oc := TOccurrence.Create;
	oc.TheWord := 'brown';
	oc.Count := 2;
	oc.FirstPos := 4;
	MyList.Add(oc);
 
	oc := TOccurrence.Create;
	oc.TheWord := 'dog';
	oc.Count := 1;
	oc.FirstPos := 10;
	MyList.Add(oc);
 
 
	oc := TOccurrence.Create;
	oc.TheWord := 'jumped';
	oc.Count := 1;
	oc.FirstPos := 14;
	MyList.Add(oc);
 
	oc := TOccurrence.Create;
	oc.TheWord := 'over';
	oc.Count := 1;
	oc.FirstPos := 21;
	MyList.Add(oc);
 
	oc := TOccurrence.Create;
	oc.TheWord := 'fence';
	oc.Count := 1;
	oc.FirstPos := 36;
	MyList.Add(oc);
	ListView1.Items.Count := MyList.Count;
end;
 
procedure TForm1.ListView1Data(Sender: TObject; Item: TListItem);
begin
	Item.Caption := TOccurrence(MyList[Item.Index]).TheWord;
	Item.SubItems.Add(IntToStr(TOccurrence(MyList[Item.Index]).Count));
	Item.SubItems.Add(IntToStr(TOccurrence(MyList[Item.Index]).FirstPos));
end;
 
procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
	MyList.Free
end;
 
end.

Open in new window

0
 

Author Comment

by:Romans
ID: 20326963
Thanks for the help - really appreciated. I added the ability to sort ascending and decending. Here is what I ended up with...

If you know how to get the little up/down arrows to appear on the top of the column headers when sorted let me know.

Thanks
Romans
unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ComCtrls, Contnrs;
 
type
  TOccurrence = class
    TheWord: string;
    Count: integer;
    FirstPos: integer;
  end;
 
 
type
  TForm1 = class(TForm)
    ListView1: TListView;
    procedure ListView1Data(Sender: TObject; Item: TListItem);
    procedure FormShow(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure ListView1ColumnClick(Sender: TObject; Column: TListColumn);
  private
    MyList : TObjectList;
 
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
  LvSortOrder: array[0..4] of Boolean; // High[LvSortOrder] = Number of Lv Columns
  SortColumn : Integer;
 
implementation
 
{$R *.dfm}
 
function SortWord(Item1,Item2 : pointer) : integer;
begin
	result := CompareText( TOccurrence(Item1).TheWord, TOccurrence(Item2).TheWord);
 
    if LvSortOrder[SortColumn] then
        Result := - Result;
end;
 
function SortCount(Item1,Item2 : pointer) : integer;
begin
	result := TOccurrence(Item1).Count - TOccurrence(Item2).Count;
 
    if LvSortOrder[SortColumn] then
        Result := - Result;
 
end;
 
function SortFirstPos(Item1,Item2 : pointer) : integer;
begin
	result := TOccurrence(Item1).FirstPos - TOccurrence(Item2).FirstPos;
 
    if LvSortOrder[SortColumn] then
        Result := - Result;
end;
 
 
procedure TForm1.ListView1Data(Sender: TObject; Item: TListItem);
begin
	Item.Caption := TOccurrence(MyList[Item.Index]).TheWord;
	Item.SubItems.Add(IntToStr(TOccurrence(MyList[Item.Index]).Count));
	Item.SubItems.Add(IntToStr(TOccurrence(MyList[Item.Index]).FirstPos));
end;
 
procedure TForm1.FormShow(Sender: TObject);
var oc  : TOccurrence;
begin
	MyList := TObjectList.Create;
 
	oc := TOccurrence.Create;
	oc.TheWord := 'The';
	oc.Count := 2;
	oc.FirstPos := 0;
	MyList.Add(oc);
 
	oc := TOccurrence.Create;
	oc.TheWord := 'brown';
	oc.Count := 2;
	oc.FirstPos := 4;
	MyList.Add(oc);
 
	oc := TOccurrence.Create;
	oc.TheWord := 'dog';
	oc.Count := 1;
	oc.FirstPos := 10;
	MyList.Add(oc);
 
 
	oc := TOccurrence.Create;
	oc.TheWord := 'jumped';
	oc.Count := 1;
	oc.FirstPos := 14;
	MyList.Add(oc);
 
	oc := TOccurrence.Create;
	oc.TheWord := 'over';
	oc.Count := 1;
	oc.FirstPos := 21;
	MyList.Add(oc);
 
	oc := TOccurrence.Create;
	oc.TheWord := 'fence';
	oc.Count := 1;
	oc.FirstPos := 36;
	MyList.Add(oc);
	ListView1.Items.Count := MyList.Count;
end;
 
procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
MyList.Free;
end;
 
procedure TForm1.ListView1ColumnClick(Sender: TObject; Column: TListColumn);
begin
    SortColumn := Column.Index;
 
	if Column.Index = 0 then
		MyList.Sort(SortWord)
	else if Column.Index = 1 then
		MyList.Sort(SortCount)
	else if Column.Index = 2 then
		MyList.Sort(SortFirstPos);
 
	ListView1.Refresh;
 
    LvSortOrder[Column.Index] := not LvSortOrder[Column.Index];
 
end;
 
end.

Open in new window

0
Gigs: Get Your Project Delivered by an Expert

Select from freelancers specializing in everything from database administration to programming, who have proven themselves as experts in their field. Hire the best, collaborate easily, pay securely and get projects done right.

 

Author Closing Comment

by:Romans
ID: 31410212
Thanks!!
0
 
LVL 14

Expert Comment

by:SteveBay
ID: 20328494
Put an imagelist on your form. Add two small images, an up arrow and a down arrow. Then put this code in your ListView1ColumnClick event

for i := 0 to ListView1.Columns.Count - 1 do
  ListView1.Columns[i].ImageIndex := -1;
if LvSortOrder[Column.Index] then
 Column.ImageIndex := 0
else
 Column.ImageIndex := 1;

0
 

Author Comment

by:Romans
ID: 20328510
Thanks Steve - Great help to me and I really appreciate it!
0

Featured Post

Gigs: Get Your Project Delivered by an Expert

Select from freelancers specializing in everything from database administration to programming, who have proven themselves as experts in their field. Hire the best, collaborate easily, pay securely and get projects done right.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Have you ever had your Delphi form/application just hanging while waiting for data to load? This is the article to read if you want to learn some things about adding threads for data loading in the background. First, I'll setup a general applica…
Hello everybody This Article will show you how to validate number with TEdit control, What's the TEdit control? TEdit is a standard Windows edit control on a form, it allows to user to write, read and copy/paste single line of text. Usua…
Along with being a a promotional video for my three-day Annielytics Dashboard Seminor, this Micro Tutorial is an intro to Google Analytics API data.
Two types of users will appreciate AOMEI Backupper Pro: 1 - Those with PCIe drives (and haven't found cloning software that works on them). 2 - Those who want a fast clone of their boot drive (no re-boots needed) and it can clone your drive wh…

805 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question