Question

Indy HTTP - MultiThreading

Asked by: darrello

I have a relatively simple question (simple for those Delphi gurus out there at least).  I am using an Indy HTTP object to access an image from a map server on the net, saving the image to a file and then loading it in my application.

However, I would like to be able to run the HTTP request and save in a separate thread because it takes a while and my users can get stuff done while it goes about it's business.  I would just maintain a link to the form that will load the image and when it is done, I would call a function with the filename to load.

I am also concerned about exception handling in the TidHTTP.Get(...) command.



A sample http link is (http://www.vwvortex.com/artman/uploads/alpine.jpg)


Currently I am using the following code (among other things I am doing):


  responseStream:=TMemoryStream.Create;
 httpIndy:=TIDHTTP.Create(nil);
 httpIndy.Host:=host;
  httpIndy.Request.ContentType:='image/jpeg';

  httpIndy.Get(url,responseStream);
  responseStream.SaveToFile(path + fileName + '.jpg');

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Asked On
2004-02-10 at 18:13:28ID20880505
Tags

multithreading

,

delphi

Topic

Delphi Programming

Participating Experts
1
Points
250
Comments
4

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Answers

 

by: StevenBPosted on 2004-02-10 at 18:44:02ID: 10328873

Something along these lines should get you started:








unit Unit1;

interface

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

type
  TJPEGLoaderThread = class(TThread)
  private
    FHost, FURL, FPath, FFileName : string;
  protected
    procedure Execute; override;
  public
    constructor Create(sHost, sURL, sPath, sFileName : String; aOnTerminate : TNotifyEvent); reintroduce;

  end;

  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    procedure LoadFinished(Sender: TObject);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses
  IdHTTP;


procedure TForm1.LoadFinished(Sender: TObject);
begin
  ShowMessage('Done');
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  TJPEGLoaderThread.Create('', 'http://www.vwvortex.com/artman/uploads/alpine.jpg', 'C:\ARSE\', 'Temp', LoadFinished);
end;

{ TJPEGLoaderThread }
constructor TJPEGLoaderThread.Create(sHost, sURL, sPath, sFileName: String; aOnTerminate : TNotifyEvent);
begin
  inherited Create(False);
  FreeOnTerminate := True;
  OnTerminate := aOnTerminate;
  FHost := sHost;
  FURL := sURL;
  FPath := sPath;
  FFileName := sFileName;
end;

procedure TJPEGLoaderThread.Execute;
var
  ResponseStream : TMemoryStream;
  HttpIndy : TIDHTTP;
begin
  inherited;
  ResponseStream := nil;
  HttpIndy := TIDHTTP.Create(nil);
  try
    ResponseStream := TMemoryStream.Create;
    HttpIndy.Host := FHost;
    HttpIndy.Request.ContentType := 'image/jpeg';
    HttpIndy.Get(FURL , ResponseStream);
    ResponseStream.SaveToFile(FPath + FFileName + '.jpg');
  finally
    FreeAndNil(ResponseStream);
    FreeAndNil(HttpIndy);
  end;
end;

end.

 

by: StevenBPosted on 2004-02-10 at 18:45:07ID: 10328881

 'C:\ARSE\' is my temp directory :o)

 

by: darrelloPosted on 2004-02-10 at 18:48:27ID: 10328901

I like the response - not so sure I like the temp directory name, I certainly hope you didn't name it for me!
cheers.

 

by: StevenBPosted on 2004-02-10 at 19:31:14ID: 10329152

 There is a long and boring story behind that name, which has nothing to do with you :o)

  I keep it now mainly because it is at the top of the folder tree and thus easy to locate.

20120131-EE-VQP-002

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