Delphi用TActionList下載文件

TActionList有個標准動作TDownLoadURL，內部是使用的URLDownloadToFile，它下載文件時會定時產生OnDownloadProgress 事件，這樣就可以用進度條顯示：

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, ExtActns, ActnList, StdCtrls, ComCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    ActionList1: TActionList;
    ProgressBar1: TProgressBar;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    procedure URL_OnDownloadProgress
              (Sender: TDownLoadURL;
              Progress, ProgressMax: Cardinal;
              StatusCode: TURLDownloadStatus;
              StatusText: String; var Cancel: Boolean) ;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure Tform1.URL_OnDownloadProgress;
begin
   ProgressBar1.Max:= ProgressMax;
   ProgressBar1.Position:= Progress;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
   with TDownloadURL.Create(self) do
   try
     URL:='http://static.cnblogs.com/images/logo_small.gif';
     FileName := 'logo.jpg';
     OnDownloadProgress := URL_OnDownloadProgress;
     ExecuteTarget(nil) ;
   finally
     Free;
   end;
   showMessage('OK');
   ProgressBar1.Max := 0;
end;