我用IDHTTP控件进行下载文件的,procedure TMainForm.IdHTTP1Work(Sender: TObject; AWorkMode: TWorkMode;
  const AWorkCount: Integer);
begin
  Application.ProcessMessages;
  self.ProgressBar1.StepBy(AWorkCount);
end;procedure TMainForm.IdHTTP1WorkBegin(Sender: TObject; AWorkMode: TWorkMode;
  const AWorkCountMax: Integer);
begin
   self.ProgressBar1.Max:= AWorkCountMax;
   self.ProgressBar1.Position := 0;
end;