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I create a PDF using iText. The content consists of text and I need to draw a line to delimit this text every 25 words as shown in the following image:

Desired result

I'm aware there's a way of that I can extract text and text positions once I have a finished PDF, but considering I'm writing the text to the PDF file, I guess there could be a way of adding these lines during the creation process without really having to find the text position, right?

Posted on StackOverflow on Feb 25, 2015 by Matias Bello

Please take a look at the Every25Words example. In that example, I read a text file into a String with the readFile() method. I then split the text into words based on the occurrence of spaces, and I add each word one by one:

public void createPdf(String dest) throws IOException, DocumentException {
    Document document = new Document();
    PdfWriter writer =
        PdfWriter.getInstance(document, new FileOutputStream(dest));
    writer.setPageEvent(new WordCounter());
    String[] words = readFile().split("\\s+");
    Chunk chunk = null;
    for (String word : words) {
        if (chunk != null) {
            document.add(new Chunk(" "));
        chunk = new Chunk(word);

The magic happens in this line:

writer.setPageEvent(new WordCounter());

First we declare an instance of the WordCounter event. You may choose a better name for that class, as not only does it count words, it also draws a dashed line:

public class WordCounter extends PdfPageEventHelper {
    public int count = 0;

    public void onGenericTag(
        PdfWriter writer, Document document, Rectangle rect, String text) {
        if (count % 25 == 0) {
            PdfContentByte canvas = writer.getDirectContent();
            canvas.setLineDash(5, 5);
            canvas.moveTo(document.left(), rect.getBottom());
            canvas.lineTo(rect.getRight(), rect.getBottom());
            canvas.lineTo(rect.getRight(), rect.getTop());
            canvas.lineTo(document.right(), rect.getTop());

Do you see what we do between the saveState() and restoreState() method? We define a dash pattern, we move to the left of the page, we construct a path to the right of the word, then we draw a short upwards line, to finish the path with a line to the right. Once the path is constructed, we stroke the line.

This onGenericTag() method will be triggered every time a Chunk is added on which we used the setGenericTag method.

This is what the result looks like every25words.pdf:

Screen shot of result

Screen shot of result

Click this link if you want to see how to answer this question in iText 7.