Delphi：列表视图中的 Shift-Up 和 Shift-Down

Question

Listview 控件中是否有可以上下移动项目的功能？

Answer 1

由于没有太多使用 TListView （我主要使用数据库网格），我将你的问题视为学习一些东西的机会。下面的代码是结果，它比大卫的答案更直观。它有一些限制：它只会移动第一个选定的项目，并且在移动项目时，移动后 vsIcon 和 vsSmallIcon 的显示很奇怪。

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;

Answer 2

您有两个选择：

• 删除它们，然后将它们重新插入到新位置。
• 使用虚拟列表视图并将它们移动到数据结构中。

我执行第一个选项的例程如下：

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;

SetListItemValues 方法用于填充列表视图的列。

这是虚拟控件为何如此出色的完美示例。