Delphi: Shift-Up and Shift-Down in the Listview

Question

Is there a feature in the Listview control to shift items up and down?

Answer 1

You have two options:

• Delete them and then re-insert them at the new location.
• Use a virtual list view and move them in your data structure.

My routine for doing the first of these options is like this:

procedure TBatchTaskList.MoveTasks(const Source: array of TListItem; Target: TListItem);
var
  i, InsertIndex: Integer;
begin
  Assert(IsMainThread);
  BeginUpdate;
  Try
    //work out where to move them
    if Assigned(Target) then begin
      InsertIndex := FListItems.IndexOf(Target);
    end else begin
      InsertIndex := FListItems.Count;
    end;

    //create new items for each moved task
    for i := 0 to high(Source) do begin
      SetListItemValues(
        FListItems.Insert(InsertIndex+i),
        TBatchTask(Source[i].Data)
      );
      Source[i].Data := nil;//handover ownership to the new item
    end;

    //set selection and focus item to give feedback about the move
    for i := 0 to high(Source) do begin
      FListItems[InsertIndex+i].Selected := Source[i].Selected;
    end;
    FBatchList.ItemFocused := FListItems[InsertIndex];

    //delete the duplicate source tasks
    for i := 0 to high(Source) do begin
      Source[i].Delete;
    end;
  Finally
    EndUpdate;
  End;
end;

The method SetListItemValues is used to populate the columns of the list view.

This is a perfect example of why virtual controls are so great.

Answer 2

Not having worked with TListView very much (I mostly use database grids), I took your question as a chance to learn something. The following code is the result, it is more visually oriented that David's answer. It has some limitations: it will only move the first selected item, and while it moves the item, the display for vsIcon and vsSmallIcon is strange after the move.

procedure TForm1.btnDownClick(Sender: TObject);
var
  Index: integer;
  temp : TListItem;
begin
  // use a button that cannot get focus, such as TSpeedButton
  if ListView1.Focused then
    if ListView1.SelCount>0 then
    begin
      Index := ListView1.Selected.Index;
      if Index<ListView1.Items.Count then
      begin
        temp := ListView1.Items.Insert(Index+2);
        temp.Assign(ListView1.Items.Item[Index]);
        ListView1.Items.Delete(Index);
        // fix display so moved item is selected/focused
        ListView1.Selected := temp;
        ListView1.ItemFocused := temp;
      end;
    end;
end;

procedure TForm1.btnUpClick(Sender: TObject);
var
  Index: integer;
  temp : TListItem;
begin
  // use a button that cannot get focus, such as TSpeedButton
  if ListView1.Focused then
    if ListView1.SelCount>0 then
    begin
      Index := ListView1.Selected.Index;
      if Index>0 then
      begin
        temp := ListView1.Items.Insert(Index-1);
        temp.Assign(ListView1.Items.Item[Index+1]);
        ListView1.Items.Delete(Index+1);
        // fix display so moved item is selected/focused
        ListView1.Selected := temp;
        ListView1.ItemFocused := temp;
      end;
    end;
end;