在 iText7 中专门为数字输入创建 PdfTextFormField

Question

I need a PdfTextFormField that can carry only numeric input as decimal values (currency). Other characters must be forbidden. Any hints can also be given in Java although I code in C#.

Answer 1

Yes, it is possible. Actually Adobe has some functions that you can use for validation (watch AFNumber_ stuff on the code below):

public void helloWorldForm() throws IOException {
    logger.info("create PDF on {}", DEST);

    final PdfWriter pdfWriter = new PdfWriter(DEST);
    final PdfDocument pdfDocument = new PdfDocument(pdfWriter);

    try (final Document document = new Document(pdfDocument)) {

        document.add(new Paragraph("Number with 2 decimal places"));

        PdfAcroForm form = PdfAcroForm.getAcroForm(pdfDocument, true);
        PdfTextFormField nameField = PdfTextFormField.createText(pdfDocument,
                new Rectangle(99, 753, 425, 15), "value", "");
        form.addField(nameField);

        PdfAction validation = PdfAction.createJavaScript("AFNumber_Format(2,0,0,0,\"\", true);");
        nameField.setAdditionalAction(PdfName.F, validation);

        validation = PdfAction.createJavaScript("AFNumber_Keystroke(2,0,0,0,\"\", true);");
        nameField.setAdditionalAction(PdfName.K, validation);

    }

    pdfDocument.close();
}

This will create a form that will only take numbers, and you can use a "." (period) for decimal places.

The PDF Reference mentions these Dictionary keys:

• PdfName.F - "A JavaScript action to be performed before the field is formatted to display its current value. This action can modify the field's value before formatting."
• PdfName.K - "A JavaScript action to be performed when the user types a keystroke into a text field or combo box or modifies the selection in a scrollable list box. This action can check the keystroke for validity and reject or modify it."

You can find some documentation on these functions on Adobe's Forms API Reference (page 119).

This mimics what you can set within Adobe Acrobat PRO:

(I have tested this method in Adobe Reader and Foxit Reader. It is possible that some reader may not support it, in which case, I would recommend you implement your own Javascript validation in a similar fashion)