Developing the Http aSync Download Sample Application

[om3raltiparmak 0]

Hi all,

 

I tried to develop the HttpAsyncDownload sample application for myself in RAD Studio 10.4 Demos-master.

 

The original application downloads the file from the URL contained in a single edit object. The filename is also being changed from another edit object. There is no error in the original application, it works smoothly.

 

I wanted to encode the application for multi download and I added a listbox of random URLs in it. The application is running, but this time it thinks it has downloaded some files and gives the information that it is complete. It also downloads some files without any problems. Also, I added a code that will remove the edit object where the filename is written, to preserve the original filename in the URL.

 

I am attaching the codes I edited below and the pas file of the original application.

 

I will be glad if you can help me with the error.

 

Example URL

https://tdsoftware.files.wordpress.com/2010/10/delphi_giris.pdf
https://dtffvb2501i0o.cloudfront.net/images/rad-studio/rad-11/RAD_11_Visuals_Set_5.png
https://dtffvb2501i0o.cloudfront.net/images/rad-studio/rad-11/smartmockups_kt2ezvfb.png
https://d3rs4yn018y0eg.cloudfront.net/tutorial/images/1470835852.jpg
https://web.itu.edu.tr/~sakarya/files/delphi.pdf

 

The Code I Edited By Myself

System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
 FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, System.Net.URLClient, System.Net.HttpClient,
 System.Net.HttpClientComponent, FMX.StdCtrls, FMX.Edit, FMX.Controls.Presentation, FMX.ScrollBox, FMX.Memo,
 System.ImageList, FMX.ImgList, FMX.Memo.Types, FMX.Layouts, FMX.ListBox;

type
 TFormDownloadDemo = class(TForm)
   PanelTop: TPanel;
   PanelCenter: TPanel;
   LabelFile: TLabel;
   BStartDownload: TButton;
   Memo1: TMemo;
   ImageList1: TImageList;
   LabelURL: TLabel;
   LabelGlobalSpeed: TLabel;
   ProgressBarDownload: TProgressBar;
   BStopDownload: TButton;
   DPath: TEdit;
   ListBox1: TListBox;
   EditFileName: TEdit;
   Label1: TLabel;
   procedure BStartDownloadClick(Sender: TObject);
   procedure ButtonCancelClick(Sender: TObject);
   procedure BStartComponentClick(Sender: TObject);
   procedure ReceiveDataEvent(const Sender: TObject; AContentLength: Int64; AReadCount: Int64; var Abort: Boolean);
   procedure FormCreate(Sender: TObject);
   procedure FormDestroy(Sender: TObject);
 private
   { Private declarations }
   FClient: THTTPClient;
   FGlobalStart: Cardinal;
   FAsyncResult: IAsyncResult;
   FDownloadStream: TStream;

   procedure DoEndDownload(const AsyncResult: IAsyncResult);
 public
   { Public declarations }
   procedure SampleDownload;
 end;

var
 FormDownloadDemo: TFormDownloadDemo;

implementation

{$R *.fmx}

uses
 System.IOUtils;

procedure TFormDownloadDemo.BStartDownloadClick(Sender: TObject);
begin
 BStartDownload.Enabled := False;
 SampleDownload;
end;

procedure TFormDownloadDemo.ButtonCancelClick(Sender: TObject);
begin
 (Sender as TButton).Enabled := False;
 FAsyncResult.Cancel;
end;

procedure TFormDownloadDemo.BStartComponentClick(Sender: TObject);
begin
 BStartDownload.Enabled := False;
 SampleDownload;
end;

procedure TFormDownloadDemo.DoEndDownload(const AsyncResult: IAsyncResult);
var
 LAsyncResponse: IHTTPResponse;
begin
 try
   LAsyncResponse := THTTPClient.EndAsyncHTTP(AsyncResult);
   TThread.Synchronize(nil,
     procedure
     begin
       Memo1.Lines.Add('Download Finished!');
       Memo1.Lines.Add(Format('Status: %d - %s', [LAsyncResponse.StatusCode, LAsyncResponse.StatusText]));
     end);
 finally
   LAsyncResponse := nil;
   FreeandNil(FDownloadStream);
   BStopDownload.Enabled := False;
   BStartDownload.Enabled := True;
 end;
end;

procedure TFormDownloadDemo.FormCreate(Sender: TObject);
begin
 FClient := THTTPClient.Create;
 FClient.OnReceiveData := ReceiveDataEvent;
end;

procedure TFormDownloadDemo.FormDestroy(Sender: TObject);
begin
 FDownloadStream.Free;
 FClient.Free;
end;

procedure TFormDownloadDemo.ReceiveDataEvent(const Sender: TObject; AContentLength, AReadCount: Int64;
 var Abort: Boolean);
var
 LTime: Cardinal;
 LSpeed: Integer;
begin
 LTime := TThread.GetTickCount - FGlobalStart;
 LSpeed := (AReadCount * 1000) div LTime;
 TThread.Queue(nil,
   procedure
   begin
     ProgressBarDownload.Value := AReadCount;
     LabelGlobalSpeed.Text := Format('Global speed: %d KB/s', [LSpeed div 1024]);
   end);
end;

procedure TFormDownloadDemo.SampleDownload;
var
 URL: string;
 LResponse: IHTTPResponse;
 LFileName, Filename: string;
 LSize: Int64;
   i: integer;
begin
 DPath.Text := TPath.GetDocumentsPath;

 i := 0;




   try

    for i := 0 to ListBox1.Items.Count-1 do
     begin


    ListBox1.ItemIndex := i;

   URL := ListBox1.Items[i];

   Filename := StringReplace(URL, '/', '\', [rfReplaceAll]);
   LFileName := TPath.Combine(DPath.Text, ExtractFileName(Filename));
   EditFilename.Text := ExtractFileName(Filename);

   LResponse := FClient.Head(URL);
   LSize := LResponse.ContentLength;
   Memo1.Lines.Add(Format('Head response: %d - %s', [LResponse.StatusCode, LResponse.StatusText]));
   LResponse := nil;

   ProgressBarDownload.Max := LSize;
   ProgressBarDownload.Min := 0;
   ProgressBarDownload.Value := 0;
   LabelGlobalSpeed.Text := 'Global speed: 0 KB/s';

   Memo1.Lines.Add(Format('Downloading: "%s" (%d Bytes) into "%s"' , [ExtractFileName(Filename), LSize, LFileName]));

   // Create the file that is going to be dowloaded
   FDownloadStream := TFileStream.Create(LFileName, fmCreate);
   FDownloadStream.Position := 0;

   FGlobalStart := TThread.GetTickCount;

   // Start the download process
   FAsyncResult := FClient.BeginGet(DoEndDownload, URL, FDownloadStream);


   end;

 finally
   BStopDownload.Enabled := FAsyncResult <> nil;
   BStartDownload.Enabled := FAsyncResult = nil;
 end;



end;

end.

 

FDownloadDemo.zip

Edited March 5, 2022 by om3raltiparmak