Author: Tomas Rutkauskas

I have a TListBox with, say, 10 strings, and I want to be able to use Drag and Drop 
to reorder those 10 items at runtime. How exactly do I do that?

Answer:

Here's the code I use to do list reordering. Create a new form, place a TListBox on 
it, set its DragMode property to dmAutomatic and connect the following event 
handlers.
1   
2   procedure TForm1.ListBox1DragDrop(Sender, Source: TObject; X, Y: Integer);
3   var
4     aListBox: TListBox;
5     DropIndex: Integer;
6   begin
7     aListBox := Sender as TListBox;
8     DropIndex := aListBox.ItemAtPos(Point(X, Y), False);
9     if aListBox.ItemIndex < DropIndex then
10      dec(DropIndex);
11    aListBox.Items.Move(aListBox.ItemIndex, DropIndex);
12    aListBox.ItemIndex := DropIndex;
13  end;
14  
15  procedure TForm1.ListBox1DragOver(Sender, Source: TObject; X, Y: Integer;
16    State: TDragState; var Accept: Boolean);
17  begin
18    Accept := Sender = ListBox1;
19  end;