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Sorting a Virtual Listview

Posted on 2007-11-20
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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.
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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;

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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.

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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.

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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

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How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails

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