TListBox. First selected element and last selected element

[LemonParty]

I think there should be methods that return first and last selected element in list box.

[ASerge]

I think there should be methods that return first and last selected element in list box.

Code: Pascal  [Select][+][-]

1. {$IFDEF WINDOWS}
2.   uses Windows, Messages;
3. {$ENDIF}
4.  
5. {$IFDEF WINDOWS}
6. procedure GetListSelInfo(AList: TListBox; out First, Last: Integer);
7. var
8.   Cnt: Integer;
9.   Sels: array of Integer = nil;
10. begin
11.   First := -1;
12.   Last := -1;
13.   if AList = nil then
14.     Exit;
15.   Cnt := AList.Count;
16.   SetLength(Sels, Cnt);
17.   Cnt := SendMessage(AList.Handle, LB_GETSELITEMS, Cnt, LPARAM(Sels));
18.   if Cnt > 0 then
19.   begin
20.     First := Sels[0];
21.     Last := Sels[Cnt - 1]
22.   end;
23. end;
24. {$ELSE}
25. procedure GetListSelInfo(AList: TListBox; out First, Last: Integer);
26. var
27.   i: Integer;
28. begin
29.   First := -1;
30.   Last := -1;
31.   if AList = nil then
32.     Exit;
33.   for i := 0 to AList.Count - 1 do
34.     if AList.Selected[i] then
35.     begin
36.       Last := i;
37.       if First < 0 then
38.         First := i;
39.     end;
40. end;
41. {$ENDIF}

[jamie]

Code: Pascal  [Select][+][-]

1.  Memo1.Text:= ListBox1.GetSelectedText;
2.  

I find it strange you only want the first and last so maybe its a miss communication?

In any case, you can use the first and Last of the GetSelectedText results which can be sent to a TStringList.

Jamie

[jamie]

You could always to a local Class hack and add this if you only need the start and end.

Code: Pascal  [Select][+][-]

1. Function ListSelectedStartEnd(Var aStart,AEnd:Integer;Const AListBox:TListBox):Boolean;Inline;
2. var
3.   L:integer;
4. Begin
5.   AStart:=-1;AEnd:=-1;
6.   With aListBox do
7.   Begin
8.   For L := 0 To Items.Count-1 do
9.    Begin
10.      If (aSTart <0)and(Selected[L])THen aSTart:=L;
11.      If (aStart>=0)and(Selected[L])Then aEnd:=L;
12.    end;
13.   end;
14.  Result := (aStart >=0);
15. end;
16.  
17. procedure TForm1.Button1Click(Sender: TObject);
18. Var
19.   S,E:integer;
20. begin
21.  if ListSelectedStartEnd(S,E,ListBox1) Then
22.  Caption := S.ToString+','+E.Tostring else
23.  Caption := 'Nothing Selected';
24. end;                                        
25.  
26.  

That should work in all platforms without change.

[Zvoni]

Jamie has it right: GetSelectedText is the easiest way

Aircode

Code: Pascal  [Select][+][-]

1. Var sl:TStringList;
2.  
3. Begin
4. .....
5.   sl:=TStringList.Create;
6.   sl.Text:=MyListBox.GetSelectedText;
7.   Writeln('First=',sl.Strings[0],'-Last=',sl.Strings[sl.Count-1);
8.  
9. End;

[LemonParty]

You could always to a local Class hack and add this if you only need the start and end.

Code: Pascal  [Select][+][-]

1. Function ListSelectedStartEnd(Var aStart,AEnd:Integer;Const AListBox:TListBox):Boolean;Inline;
2. var
3.   L:integer;
4. Begin
5.   AStart:=-1;AEnd:=-1;
6.   With aListBox do
7.   Begin
8.   For L := 0 To Items.Count-1 do
9.    Begin
10.      If (aSTart <0)and(Selected[L])THen aSTart:=L;
11.      If (aStart>=0)and(Selected[L])Then aEnd:=L;
12.    end;
13.   end;
14.  Result := (aStart >=0);
15. end;
16.  
17. procedure TForm1.Button1Click(Sender: TObject);
18. Var
19.   S,E:integer;
20. begin
21.  if ListSelectedStartEnd(S,E,ListBox1) Then
22.  Caption := S.ToString+','+E.Tostring else
23.  Caption := 'Nothing Selected';
24. end;                                        
25.  
26.  

That should work in all platforms without change.

I can write a loop that finds the first and the last one by myself, but it would be great if there is a method from the box. And this methods may find the n-th selected element from begin / end, that is better than just the last one and the first one.

[Zvoni]

You could always to a local Class hack and add this if you only need the start and end.

Code: Pascal  [Select][+][-]

1. Function ListSelectedStartEnd(Var aStart,AEnd:Integer;Const AListBox:TListBox):Boolean;Inline;
2. var
3.   L:integer;
4. Begin
5.   AStart:=-1;AEnd:=-1;
6.   With aListBox do
7.   Begin
8.   For L := 0 To Items.Count-1 do
9.    Begin
10.      If (aSTart <0)and(Selected[L])THen aSTart:=L;
11.      If (aStart>=0)and(Selected[L])Then aEnd:=L;
12.    end;
13.   end;
14.  Result := (aStart >=0);
15. end;
16.  
17. procedure TForm1.Button1Click(Sender: TObject);
18. Var
19.   S,E:integer;
20. begin
21.  if ListSelectedStartEnd(S,E,ListBox1) Then
22.  Caption := S.ToString+','+E.Tostring else
23.  Caption := 'Nothing Selected';
24. end;                                        
25.  
26.  

That should work in all platforms without change.

I can write a loop that finds the first and the last one by myself, but it would be great if there is a method from the box. And this methods may find the n-th selected element from begin / end, that is better than just the last one and the first one.

GetSelectedText is a full string you can assign to a StringList.
Look there…..

And noone prevents you to write a classhelper

[jamie]

One must remember that the Listbox can have random selections, they don't always have them listed contiguously.

This means if you are interested in the complete range of selections, there could be some in the middle not selected.

 But there is always that chance that maybe the object pointers of each entry is also of interest.


Jamie

[Aruna]

Hello Everyone,

A bit late to the discussion, but I’ve put together two sample projects that should help illustrate what everyone’s been talking about. There are multiple ways a user can click and select items in a TListBox.

The first example (shown in the first screenshot) demonstrates the simple case, tracking only the first and last selected elements.

As Jamie rightly pointed out, “One must remember that the ListBox can have random selections; they aren't always contiguous.” The second example (and its corresponding screenshot) handles exactly that scenario.

Hope this helps!