Greetings,
I have two listboxes on a form; each has a vertical scrollbar. I am
trying to understand how to read the selected item. In Delphi, does the
user have to scroll thru listbox list and then select the item in the
listbox before the program recognizes an item has been selected? That
seems to be one step too many; the user should just have to scroll thru
the list then stop at the item of choice.

If there's an event or property for the listboxes that I can use to read
the selection w/o the user having to scroll AND select?

Best,
Bill

You should be able to read the selected item regardless of whether the user
has scrolled the listbox or clicked on it.  Of course, when a list box is
initially created and then populated, there is no "default" selected item,
so either your application or the user must select an item in the list box
as the "selected" item in order for you to recognize it in your code.

To get the currently selected item, use:

var
  SelectedItem : String;
begin
  If (ListBox1.ItemIndex >= 0) Then
      SelectedItem := ListBox1.Items[ListBox1.ItemIndex];

Of couse, you must check if ItemIndex <> -1 first before referencing items
using that property.  If ItemIndex >= 0, then you can get the selected item.
If ItemIndex = -1, then no item has been selected and you should not try to
use ItemIndex as an index into the Items array.

Your app can initially set the first item in the list as the default
selected item by using the following code after the list has already been
populated:

If (Listbox1.Items.Count > 0) Then
    ListBox1.ItemIndex := 0;

Hope this helps.

--
Vinnie Murdico
Software with Brains, Inc.
SWBTracker - Professional Bug Tracking Software
http://www.softwarewithbrains.com

Thanks for your reply. I used your code example to get the values but I
still only get the listbox values to update when the user both scrolls
then selects an entry from the list. I use showmessage() to test the
code.

Here's some of the code:
I initially populate listboxes and radiogroup with default values in
FormCreate:

procedure TMainForm.FormCreate(Sender: TObject);
begin     lbDimension.ItemIndex := 1;
  lbKernel.ItemIndex := 0;
  rgEmbedState.ItemIndex := 2;
  rbClose.Checked := true;
end;

The user can make parameter selections from the listboxes or accept the
default values. He then hits a button to start the simulation.

procedure TMainForm.bStartClick(Sender: TObject);
//At this point in the program, the user has seleected
//a file and should have selected all the inputs
var
  i, j : integer;
  strKernel, dimen : string;
begin        //grab the dimension
  If (lbDimension.ItemIndex >= 0) Then
      dimen := lbDimension.Items[lbDimension.ItemIndex];
      showmessage('Here is dimension ' + dimen);

//grab the kernel type
  If (lbKernel.ItemIndex >= 0) Then
      strkernel := lbKernel.Items[lbKernel.ItemIndex];
      showmessage('Here is Kernel ' + strKernel);

//grab the dimension
  If (lbDimension.ItemIndex >= 0) Then
      strkernel := lbDimension.Items[lbDimension.ItemIndex];
      showmessage('Here is strkernel ' + strkernel);

....

When I run this code, the background color of the listboxes on my
mainform is green and when I press the StartSimulation button, the
showmessages display the correct values. However, when I change a value
in a listbox by using the scrollbar, the background color changes to
white but when I run the code again the showmessages don't update and
show the new values I've selected.  Only when I click on the field
inside the listbox (which turns the background color green) will the
showmessage display the correct (updated) values.

I don't know what's going on...

Bill

"Vinnie Murdico" <vin...@softwarewithbrainsSPAMKILL.com> wrote in
message news:4zWdnSTNAZgumqejXTWc3w@gbronline.com...

In article <Xjm_9.6267$ZX5.169...@twister.austin.rr.com>, "William Vedder"

Any item in a TListBox is selected by clicking on the displayed item. Once an
item has been selected, then TListBox.ItemIndex is set to the index of the
selected item. That selection and ItemIndex remains as ir was set even if the
listbox is scrolled.

The user can select an item _only_ by clicking on it (multi-select selects
additional items by clicks with a modifier key).

While a TListBox has a TopIndex which reads or sets the item at the top of a
displayed listbox, one cannot sense when a mouse-up occurs on the scroll-bar so
that one might select the top item on that event for example.

I think you cannot do what you appear to want to do.

Alan Lloyd
alangll...@aol.com

Thanks Alan.  I was hoping that there was an "onchange" event or
something that I was missing.  It seems senseless to have to scroll AND
select.

Best,
Bill

news:20030201085805.04274.00000054@mb-co.aol.com...

Please don't include attached files with your messages. Post the code if
necessary (and not too long).

In article <fuV_9.12285$2y.582...@twister.austin.rr.com>, "William Vedder"

But how do you know which (of the many items displayed when scrolling) the user
wants to select. Or are you displaying only one item as the scrolling takes
place. If that's the case, then there are other ways of doing that sort of
thing.

Alan Lloyd
alangll...@aol.com

Yes, I have sized the listboxes such that the user sees only one item at
a time. I am interested to hear other suggestions besides a listbox... I
looked at doing this w/ radio buttons but that's ugly.

Bill

news:20030201150949.18097.00000393@mb-mc.aol.com...

I apologize for the attachment but that's not what I sent or at least
intended to send. I cut/pasted some code into my email response. I don't
know how it ended up as an attachment.

Best,
Bill
"John of Aix" <j.murphyNOS...@libertysurf.fr> wrote in message
news:b1h87g$12t1si$13@ID-157326.news.dfncis.de...

This screams for a dropdown-listbox (a specific style of combobox).

In normal listboxes, you can scroll the selection out of sight.
That can be somewhat useful sometimes.

A propos the radio buttons versus the dropdown-listbox, this is
the exact difference between NT4's and NT5's logoff dialogs.
In NT4, you can _see_ the options without clicking anything. As
a result, I can pick them blindly using the cursor keys. This is
convenient. In NT5, not only do I need more motions, but I have
to read the list anew every time. It just doesn't stick. This is
_not_ convenient.

Groetjes,
Maarten Wiltink

In article <CBX_9.12382$2y.610...@twister.austin.rr.com>, "William Vedder"

A TStringList, a read-only TEdit, and a TUpDown would IMO be the best as
follows ...

var
  MyStrList : TStringList;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Edit1.AutoSelect := false;   // ... or set in IDE
  Edit1.ReadOnly := true;      // ... or set in IDE
  {create a TStringList with the user options}
  MyStrList := TStringList.Create;
  MyStrList.Text := 'One'#13'Two'#13'Three'#13'Four'#13'Five';
  {set the UpDown}
  UpDown1.Min := 0;
  UpDown1.Max := MyStrList.Count - 1;
  UpDown1.Position := 0;
  {display first selection}
  UpDown1Click(nil, btNext);
end;

procedure TForm1.UpDown1Click(Sender: TObject; Button: TUDBtnType);
begin
  Edit1.Text := MyStrList.Strings[UpDown1.Position];
end;

Alan Lloyd
alangll...@aol.com

It's not *that* bad as you can select a combo box entry
by typing its initial letter. Nevertheless the old design
was better IMHO, too.
Uli.