Delphi中的TActionList有个标准动作TDownLoadURL，内部是使用的URLDownloadToFile，它下载文件时会定时产生OnDownloadProgress 事件，这样就可以用进度条显示。
本文讲述了Delphi用TActionList实现下载文件的方法，实现代码如下所示：
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:='https://www.jb51.net/images/logo.gif';
FileName := 'logo.gif';
OnDownloadProgress := URL_OnDownloadProgress;
ExecuteTarget(nil) ;
finally
Free;
end;
showMessage('OK');
ProgressBar1.Max := 0;
end;
