How to extract fieldname of PdfFormField from PdfAnnotation

Question

So I create a radio group using this PdfFormField.createRadioButton() then calling the setFieldName().

However, the PdfAnnotation does not show any keys that stores the field name. I looked at the other dictionaries inside the PdfAnnotation but could not find any.

reader.getAcroFields().getFields().keySet() does list the field names of the form fields but I wish to ask if there is any way via PdfAnnotation?

I tried to put a custom PdfName inside the radio group object but it does not show up in the PdfAnnotation's dictionary.

Answer 1

You are confusing the concept of an annotation (link annotation, file attachment annotation, widget annotation,...) and a form field (text field, choice field, button field, signature field).

In iText 5, annotations are dealt with in a class named PdfAnnotation; form fields are dealt with in a class named PdfFormField. You are trying to do something that is specific for a PdfFormField using the class PdfAnnotation. That's wrong.

I understand the root of the confusion: every visible form field corresponds with at least one widget annotation. Most of the visible form fields correspond with exactly one widget annotation. That's why we made a design choice in iText 5 to have PdfFormField extends PdfAnnotation.

This design choice is in line with the PDF specification where it says that field dictionaries of fields that correspond with a single widget annotation may be merged into a single PDF dictionary.

In practice, you will find PDF dictionaries in a PDF that combine entries typical for a widget annotation dictionary and a field dictionary. (That also explains why there's a getMerged() method in iText: that method gets you the merged dictionary objects.)

I hope this already explains part of your problem. You seem to have another problem too, but I don't understand what you want to do. Please clarify using references to ISO-32000-1 so that people can understand which technical feature you are trying to implement.