Load rows into listview from an OpenDialog

The LoadFromFile method is not available in Listview , what you can do is load the file information into StringList and popular Listview with TListItem . Here's an example:

procedure AddItemsListview(Listview: TListView; Arquivo: string);
Var
  Items: TStringList;
  Item: TListItem;
  I: Integer;
begin
Items := TStringList.Create;
try
  Items.LoadFromFile(Arquivo);
  for I := 0 to Items.Count -1 do begin
    Item := Listview.Items.Add;
    Item.Caption := Items[I]; // Coloca o valor na primeira coluna do Listview
  end;
finally
  Items.Free;
end;
end;

And to use the above method, assuming you've already added% with%, do the following:

procedure TForm1.Button1Click(Sender: TObject);
begin
OpenDialog1.InitialDir := ExtractFilePath(ParamStr(0)); // Abre o diálogo no diretório do programa
OpenDialog1.Filter := 'Arquivos de texto (.txt) | *.txt'; // Somente arquivos de texto

if OpenDialog1.Execute = false then exit;
AddItemsListview(ListView1, OpenDialog1.FileName);
end;