Author: Lou Adler

I'm populating a treeview from a folder location. At this moment I know how to scan 
that folder for files and other folders. How can I perform a search so that the 
items get grouped first the folders and then the files (like Windows Explorer)?

Answer:

You have basically two options:

Do two separate scans, one for folders only, one for files only. This way the 
treeview gets populated in two chunks. But the two sections will not be sorted 
alphabetically or so, since the order in which Findfirst/FindNext retrieves the 
files/folders is undefined (or better: nobody outside MS knows how it is defined ).

or

Sort the treeview after you have populated it using a single scan. By blocking the 
treeview from redrawing while you populate it (Items.beginUpdate/items.endupdate) 
you can do populating and sorting without any visual upheaval.

You do the sorting by calling the handling CustomSort method of the treeview. There 
are two ways to use it, you can hand it a custom comparison function or you can let 
it call the treeviews OnCompare event to get a descision fromn you which node of a 
pair to consider "larger". The second method may be easier for you, so you would 
construct you treeview population code like

1   { ... }
2   treeview1.items.beginupdate;
3   try
4     PopulateTreeView;
5     treeview1.CustomSort(nil, 0);
6   finally
7     treeview1.items.endupdate;
8   end;
9   { ... }


and handle the OnCompare event to compare two nodes. The comparison would inspect 
two items of data for each node: whether it is a folder node or not, and the nodes 
Text. So you need some way to indicate that a node stands for a folder. You could 
use the nodes Data property for that, e.g. store Pointer(1) into it for a folder 
and Nil (Pointer(0)) for a file. In this case the compare event handler would be 
this:
10  
11  procedure TForm1.TreeView1Compare(Sender: TObject; Node1, Node2: TTreeNode;
12    Data: Integer; var Compare: Integer);
13  begin
14    if node1.Data = node2.Data then
15      compare := AnsiCompareText(Node1.Text, NOde2.Text)
16    else if Assigned(node1.data) then
17      compare := -1 {folders sort before files}
18    else
19      compare := 1;
20  end;