Delphi HTMLParser - Sample 1 - Reading tags

July 30th, 2007 by William Yang

HTMLParser is really easy to use. I have made an sample project for anyone who likes to use HTMLParser for their project.

Assume you have downloaded HTMLParser , and have extracted the files into your library directory.

First you need to drop the following items to your form.

  • Memo1: TMemo;
  • Edit1: TEdit;
  • OpenDialog1: TOpenDialog;
  • Button1: TButton;
  • Button2: TButton;
  • txtTitle: TEdit;
  • txtDescription: TEdit;
  • txtKeywords: TEdit;
  • Memo2: TMemo;

HTMLParser Sample 1 - reading tag screenshot

2. Add the following code.

Show Code

  1. procedure TForm1.Button1Click(Sender: TObject);
  2. begin
  3.   if (OpenDialog1.Execute) then
  4.   begin
  5.     Memo1.Lines.LoadFromFile(OpenDialog1.FileName);
  6.   end;
  7. end;
  8.  
  9. procedure TForm1.FormCreate(Sender: TObject);
  10. begin
  11.   fHTML := THTMLObject.Create;
  12. end;
  13.  
  14. procedure TForm1.FormDestroy(Sender: TObject);
  15. begin
  16.   fHTML.Free;
  17. end;
  18.  
  19. procedure TForm1.Memo1Change(Sender: TObject);
  20. begin
  21.   fHTML.LoadFromStrings(Memo1.Lines);
  22.   UpdateFields;
  23. end;

3. Create a new procedure in Form1.

This method is used to make calls to fHTML to get TITLE tag, Description and Keywords meta tag

Show Code

  1. procedure TForm1.UpdateFields;
  2. var
  3.   i: Integer;
  4.   metatag: TTagObject;
  5. begin
  6.   //Get title content, just like in Javascipt, tagobject has innerText property
  7.   txtTitle.Text := fHTML.TagByName['TITLE'].innerText;
  8.   //Specify which tag we need look for
  9.   fHTML.TagName := 'META';
  10.   // Reset tag array index to first
  11.   fHTML.First;
  12.   // Look for next META tag
  13.   metatag := fHTML.Next;
  14.   while metatag <> nil do
  15.   begin
  16.     if metatag.CompareValue('NAME', 'DESCRIPTION') or metatag.CompareValue('HTTP-EQUIV', 'DESCRIPTION') then
  17.     begin
  18.       txtDescription.Text := metatag.ReadString('CONTENT', '');
  19.     end else
  20.     if metatag.CompareValue('NAME', 'KEYWORDS') or metatag.CompareValue('HTTP-EQUIV', 'KEYWORDS') then
  21.     begin
  22.       txtKeywords.Text := metatag.ReadString('CONTENT', '');
  23.     end;
  24.     metatag := fHTML.Next;
  25.   end;
  26. end;

4. At this point you can already run this program, you should be able click Browse (button1) to parse any file on your computer or paste the HTML content from clipboard.

The following code is to show you how to get all A tags from an HTML content

Show Code

  1. procedure TForm1.Button2Click(Sender: TObject);
  2. var
  3.   i: Integer;
  4.   metatag: TTagObject;
  5. begin
  6.   fHTML.TagName := 'A';
  7.   // Reset tag array index to first
  8.   fHTML.First;
  9.   // Look for next A tag
  10.   metatag := fHTML.Next;
  11.   Memo2.Lines.Clear;
  12.   while metatag <> nil do
  13.   begin
  14.     Memo2.Lines.Add(metatag._RS('href', '(empty url)'));
  15.     metatag := fHTML.Next;
  16.   end;
  17. end;

Download full source code

This entry was posted on Monday, July 30th, 2007 at 11:13 pm and is filed under Delphi code. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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2 comments to “Delphi HTMLParser - Sample 1 - Reading tags”

  1. Comment by Sam:
    Monday, August 13th 2007 at 11:52 am

    [Error] Unit1.pas(69): Illegal character in input file: ‘&’ ($26)

    in procedure TForm1.UpdateFields;
    …..
    while metatag <> nil do
    …..

  2. Comment by William:
    Friday, August 24th 2007 at 11:41 pm

    Hi Sam:

    Is this compiling time error? If is, what Delphi version are you using?

    I know the code compiles without any errors on Delphi v7.

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