AcroForm and AcroField PLUS FAQ ENTRY 2006-08-31 - By Mark Storer
Back
I'm pretty sure this is in the FAQ somewhere. Thought I don't know the FAQ URL
off the top of my head... lets see here... It's not there. I'm shocked.
But there is a form for submitting FAQs:
<site:faq-entry name="Why do forms behave strangely when I merge them?">
<site:question>When I merge two forms together, different copies of the same
name have the same value. What can I do to maintain seperate copies of the
fields within the same form?</site:question>
<site:answer>
All fields in a PDF file with the same name share a value. This becomes
obvious when two copies of a form try to coexist within a single PDF, but can
be a relatively subtle problem with common field names ("Name", "Address" and
so forth).
This problem can be further obscured by iText when it is asked to generate
field appearances. The individual appearances will contain the corresponding
value until one of them is edited. At that time, Reader will update all the
fields to hold the new value. From Reader's point of view, they always shared
a value and merely had inaccurate appearances. JavaScript asked to retrieve a
given field's value will return that single value.
There are two solutions if you absolutely must merge forms:
1) Flatten the individual instances of the form, save them, then stitch them
all together.
Flattened forms aren't really forms anymore, they're regular PDFs that happen
to look like one. They aren't editable, and there's no script, calculations,
or formatting (which can be a problem). You don't need PdfCopyForm, PdfCopy
alone will work. In fact, you can merge a single normal form together with any
number of flattened forms.
2) Rename all the fields.
For all but the simplest forms, you should strive to avoid merging them unless
you know EXACTLY what you are doing, and can plan for it.
Develop some name-mangling scheme and consistently apply it to your fields as
you import them. Something like appending "__#" where the # is an ID number.
This avoids name collisions. You'll have to bone up on the PdfReference and
manipulate PdfDictionary objects directly. Further, this must be done before
attaching them to an instance of PdfCopyForm. Once a PdfWriter is attached to
a PdfReader, you can't be sure that any changes you make will "stick".
There are problems with renaming fields. Firstly, most field scripts are
written with specific field names in mind. Furthermore, some signatures key
off field names, but merging them will invalidate those signatures no matter
what you do.
Assuming for a moment that you have control over the initial PDF forms you'll
be using, you can rewrite your scripts to recognise which instance of a
particular field is the appropriate one. In field events, you can check the
current field's name to see how to access other fields from the same form.
Parse out the mangled name, and use it to determine the name of the appropriate
field form the same form. Document level scripts and events are more
challenging though it should be possible to set a global on each page's "Page
Open" event and access the appropriate fields that way.
If you do not have control over the forms and cannot rewrite their script,
there's not much you can do programmatically. The moment someone builds a
field name from parts (getField("quantity_" + rowNum)), it's effectively
impossible to fix in a general way. Specific cases may be more tractable.
</site:answer>
</site:faq-entry>
--Mark Storer
Senior Software Engineer
Cardiff Software
#include <disclaimer>
typedef std::Disclaimer<Cardiff> DisCard;
> -- --Original Message-- --
> From: itext-questions-bounces@(protected)
> [mailto:itext-questions-bounces@(protected)]On
> Behalf Of Henry
> Doan
> Sent: Thursday, August 31, 2006 9:47 AM
> To: itext-questions@(protected)
> Subject: [iText-questions] AcroForm and AcroField
>
>
> Hi i am coping the same pdf file into one big one and each
> time i copy them
> in I fill out the form field uniquely, and it shows up too.
> But when i try
> to change the form field inside a browser on one pdf page it
> changes on all
> of the other pdf page too.
>
>
> Heres my code:
>
> // FOR COPYING FORMS
> PdfCopyFields copy = new PdfCopyFields(baos);
> // GET THE FILE
> PdfReader reader2 = null, reader = new PdfReader("e:/myFile.pdf");
>
> int tmp =0;
> while (tmp <= 5){
> // WRITE TO PDF
> reader2 = new PdfReader("e:/Webs/walton/ICF.pdf");
> stamp1 = new PdfStamper(reader2, baos2);
> acroField = stamp1.getAcroFields();
> acroField.setField("Name", strName);
>
> stamp1.close();
> reader.close();
>
> //write to baos then read from it and copy it to [copy]
> reader2 = new PdfReader(baos2.toByteArray());
> copy.addDocument(reader2);
> tmp++;
> }
>
> Thank you,
>
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