unit Unit1;

 interface

 uses

   Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,

   Vcl.Controls, Vcl.Forms, Vcl.Dialogs, IdComponent, Vcl.ComCtrls, Vcl.StdCtrls,

   IdAntiFreezeBase, IdAntiFreeze, IdBaseComponent, IdTCPConnection, IdTCPClient,

   IdHTTP;

 type

   TForm1 = class(TForm)

     Label1: TLabel;

     Label2: TLabel;

     Edit1: TEdit;

     Edit2: TEdit;

     IdHTTP1: TIdHTTP;

     IdAntiFreeze1: TIdAntiFreeze;

     Button1: TButton;

     ProgressBar1: TProgressBar;

     Label3: TLabel;

     Label4: TLabel;

     Label5: TLabel;

     Label6: TLabel;

     procedure IdHTTP1WorkBegin(ASender: TObject; AWorkMode: TWorkMode;

       AWorkCountMax: Int64);

     procedure IdHTTP1Work(ASender: TObject; AWorkMode: TWorkMode;

       AWorkCount: Int64);

     procedure Button1Click(Sender: TObject);

   private

     { Private declarations }

   public

     { Public declarations }

   end;

 var

   Form1: TForm1;

 implementation

 {$R *.dfm}

 //1. 字节数转换为KB或MB字符串

 function BytesToStr(iBytes: Integer): String;

 var

   iKb: Integer;

 begin

   iKb := Round(iBytes / );

   if iKb >  then

     Result := Format('%.2f MB', [iKb / ])

   else

     Result := Format('%d KB', [iKb]);

 end;

 procedure TForm1.IdHTTP1WorkBegin(ASender: TObject; AWorkMode: TWorkMode;

   AWorkCountMax: Int64);

 begin

   ProgressBar1.Max := AWorkCountMax;                // 获取要下载的文件大小

   Label2.Caption := BytesToStr(AWorkCountMax);

   Update;

 end;

 procedure TForm1.IdHTTP1Work(ASender: TObject; AWorkMode: TWorkMode;

   AWorkCount: Int64);

 begin

   Label1.Caption := BytesToStr(aWorkCount);      //更新进度

   ProgressBar1.Position := aWorkCount;           //更新进度条

   Update;

 end;

 procedure TForm1.Button1Click(Sender: TObject);

 var

   tStream: TMemoryStream;

 begin

   tStream := TMemoryStream.Create;

   try

     IdHTTP1.Get(Edit1.Text, tStream);       //保存到内存流 （下载链接）

     tStream.SaveToFile(Edit2.Text);         //保存为文件  （路径）

     ShowMessage('下载成功！');

   except

     ShowMessage('下载失败！');

   end;

   tStream.Free;

 end;

 end.