How to decide the right coordinates in the middle of a PDF page? - itext

Question

I am new to iText and I looked at its many examples. The thing I have hard time to figure it out is the rectangle. On the page
http://developers.itextpdf.com/examples/form-examples-itext5/multiline-fields
there are many examples with hard-coded values for Rectangle objects. For example:
Rectangle rect = new Rectangle(36, 770, 144, 806);
My problem is that I create one Paragraph and I would like to add a fillable text input box (multi-lines) beneath it. How do I know the exact values for creating a Rectangle object that can be nicely put just after the paragraph. The size of the text of a Paragraph can change. So I cannot assume any hard-coded value.

Answer 1

In iText 5, iText keeps track of the coordinates of the content when using document.add(). You could take control yourself by adding content at absolute positions (e.g. by using ColumnText), but that's hard, because then you have to keep track of many things yourself (for instance: you have to introduce page breaks yourself when the content reaches the bottom of the page).
If you leave the control of the coordinates to iText, you can get access to these coordinates by using page events.
Take a look at the example below, where we keep track of the start and the end of a Paragraph in the onParagraph() and onParagraphEnd() method. This code sample is not easy to understand, but it's the only way to get the coordinates of a Paragraph in iText 5 for instance if we want to draw a rectangle around a block of text. As you can read at the bottom of that page, iText 7 makes it much easier to meet this requirement.
If you stick to iText 5, it's much easier to use generic tags to define locations. See the GenericFields example, where we use empty Chunks that result in fields. If you want to see a screen shot of the result, see Add PdfPCell to Paragraph
In your case, I'd create a Paragraph containing a Chunk that spans different lines, and I'd add the field in the onGenericTag() method of a page event.
Suppose that we have the following text file: jekyll_hyde.txt
How do we convert it to a PDF that looks like this:
Note the blue border that is added to the titles, and the page number at the bottom of each page. In iText 5, these elements are added using page events:
class MyPageEvents extends PdfPageEventHelper {
protected float startpos = -1;
protected boolean title = true;
public void setTitle(boolean title) {
this.title = title;
}
#Override
public void onEndPage(PdfWriter writer, Document document) {
Rectangle pagesize = document.getPageSize();
ColumnText.showTextAligned(
writer.getDirectContent(),
Element.ALIGN_CENTER,
new Phrase(String.valueOf(writer.getPageNumber())),
(pagesize.getLeft() + pagesize.getRight()) / 2,
pagesize.getBottom() + 15,
0);
if (startpos != -1)
onParagraphEnd(writer, document,
pagesize.getBottom(document.bottomMargin()));
startpos = pagesize.getTop(document.topMargin());
}
#Override
public void onParagraph(PdfWriter writer, Document document,
float paragraphPosition) {
startpos = paragraphPosition;
}
#Override
public void onParagraphEnd(PdfWriter writer, Document document,
float paragraphPosition) {
if (!title) return;
PdfContentByte canvas = writer.getDirectContentUnder();
Rectangle pagesize = document.getPageSize();
canvas.saveState();
canvas.setColorStroke(BaseColor.BLUE);
canvas.rectangle(
pagesize.getLeft(document.leftMargin()),
paragraphPosition - 3,
pagesize.getWidth() - document.leftMargin() - document.rightMargin(),
startpos - paragraphPosition);
canvas.stroke();
canvas.restoreState();
}
}
We can use the following code to convert a text file to a PDF and introduce the page event to the PdfWriter:
public void createPdf(String dest)
throws DocumentException, IOException {
Document document = new Document();
PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(dest));
MyPageEvents events = new MyPageEvents();
writer.setPageEvent(events);
document.open();
BufferedReader br = new BufferedReader(new FileReader(TEXT));
String line;
Paragraph p;
Font normal = new Font(FontFamily.TIMES_ROMAN, 12);
Font bold = new Font(FontFamily.TIMES_ROMAN, 12, Font.BOLD);
boolean title = true;
while ((line = br.readLine()) != null) {
p = new Paragraph(line, title ? bold : normal);
p.setAlignment(Element.ALIGN_JUSTIFIED);
events.setTitle(title);
document.add(p);
title = line.isEmpty();
}
document.close();
}
Source: developers.itextpdf.com