unit Unit3;

interface

uses

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

  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, System.Net.HttpClient,

  Vcl.ComCtrls;

type

  TForm3 = class(TForm)

    btnStart: TButton;

    ProgressBar1: TProgressBar;

    edt1: TEdit;

    procedure btnStartClick(Sender: TObject);

    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);

    procedure FormShow(Sender: TObject);

    procedure FormCreate(Sender: TObject);

  private

    { Private declarations }

    ///

    /// 下载的时候不允许关闭窗体

    ///

    FAllowFormClose: Boolean;

    ///

    /// 接收数据事件

    ///

    procedure ReceiveDataEvent(const Sender: TObject; AContentLength: Int64; AReadCount: Int64; var Abort: Boolean);

  public

    { Public declarations }

  end;

var

  Form3: TForm3;

implementation

{$R *.dfm}

procedure TForm3.ReceiveDataEvent(const Sender: TObject; AContentLength: Int64; AReadCount: Int64; var Abort: Boolean);

begin

  //加上这句界面不卡死.

  Application.ProcessMessages;

  ProgressBar1.Position := AReadCount;

end;

procedure TForm3.btnStartClick(Sender: TObject);

var

  MyHTTPClient: THTTPClient;

  MyHTTPResponse: IHTTPResponse;

  MyMemoryStream: TMemoryStream;

  downloadUrl: string;

begin

  MyHTTPClient := THTTPClient.Create;

  MyMemoryStream := TMemoryStream.Create;

  try

    btnStart.Enabled := False;

    FAllowFormClose := False;

    downloadUrl := Trim(edt1.Text);

    //获取文件的大小

    MyHTTPResponse := MyHTTPClient.Head(downloadUrl);

    ProgressBar1.Position := 0;

    ProgressBar1.Max := MyHTTPResponse.ContentLength;

    //开始下载,保存到本地

    MyHTTPClient.OnReceiveData := ReceiveDataEvent;

    MyHTTPResponse := MyHTTPClient.Get(downloadUrl, MyMemoryStream);

    if MyHTTPResponse.StatusCode = 200 then

    begin

      MyMemoryStream.SaveToFile('c:\aa.exe');

      ShowMessage('下载完成');

    end;

  finally

    MyHTTPClient.Free;

    MyMemoryStream.Free;

    //最终都允许关闭窗体

    btnStart.Enabled := True;

    FAllowFormClose := True;

  end;

end;

procedure TForm3.FormCloseQuery(Sender: TObject; var CanClose: Boolean);

begin

  CanClose := FAllowFormClose;

end;

procedure TForm3.FormCreate(Sender: TObject);

begin

  ReportMemoryLeaksOnShutdown := True;

end;

procedure TForm3.FormShow(Sender: TObject);

begin

  btnStart.Enabled := True;

  FAllowFormClose := True;

  ProgressBar1.Position := 0;

end;

end.