Why moving ItemIndex of FileListBox in runtime, filelistbox1.FileName
is blank
lazarus / 16-Databases

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asdf · 2012-12-04 09:51

Code: [Select]var
u: integer;
load1: string;

begin
for u:=0 to filelistbox1.Count-1 do begin;
    filelistbox1.ItemIndex:=u;
    load1:= filelistbox1.FileName;

    memo1.Append('1. u = '+inttostr(u));
    memo1.Append('2. Load1 = '+load1);
    memo1.Append('3. '+filelistbox1.FileName;
    memo1.Append(' ');                       
Why moving ItemIndex by 'u' gave the 'filelistbox1.FileName' blank ?
On the other hand, clicking on it by mouse, it gave the correct
filename.

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User137 · 2012-12-04 10:47

If you check the components code internally, filename is made like
this:
Code: [Select]FFileName:= FDirectory+DirectorySeparator+FFileName;
So if you don't want to call FileListBox1.UpdateFileList; , which i
don't recommend (because that command may be slow, especially if
directory is large), you can change the code to roughly this:
Code: [Select]for u:=0 to filelistbox1.Count-1 do begin;
    load1:= filelistbox1.Directory + DirectorySeparator +
filelistbox1.Items[u];
edit: And also, what you found is a bug. There is no setter function
to Itemindex property, so filename isn't updated realtime. It could be
event-driven, Application.Processmessages might update it too.

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asdf · 2012-12-04 22:29

If so, do I have to change 'all' I have ever written like this ...
Code: [Select]    load1:= filelistbox1.FileName;
to be like this ...
Code: [Select]load1:= filelistbox1.Directory + DirectorySeparator +
filelistbox1.Items[u];   ?

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User137 · 2012-12-04 23:33

You have a for-loop which goes through all the files. Itemindex was
never intended to be changed like that, and so often. So it is much
better and faster way to use the .Items[] property.

If you don't change Itemindex in code, then you should be ok to use
.Filename.

There's internal function UpdateSelectedFileName; but it's private,
and so you can't use it. UpdateFileList; does that, but it also
searches the entire folder for files, so that's why i don't recommend
using that in a for-loop, especially one that depends on amount of
files in that folder.

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asdf · 2012-12-04 23:55

Thank you so much   .