Different Leading for each page in itext 7

Question

How i can set different fixedLending on specific page page ? How i can specific page when i add a paragraph?

 String line = "Hello! Welcome to iTextPdf";
    Div div = new Div();
        for (int i = 0; i < 30; i++) {
            Paragraph element = new Paragraph();
            element.add(line + " " + i);
      

            paragraphs.add(element);

        }

  
--------------
      if(page==1) // This is just for an example. How I want it to be
       element.setFixedLeading(100);
       else if(page==3)
     element.setFixedLeading(50);

After adding paragraphs, I need to do different setFixedLeading for the first and third page

Answer 1

You need a custom renderer for it - the renderer knows the context in which the element is going to be placed. Here is example code:

private static class VariableLeadingParagraphRenderer extends ParagraphRenderer {
    public VariableLeadingParagraphRenderer(Paragraph modelElement) {
        super(modelElement);
    }

    @Override
    public LayoutResult layout(LayoutContext layoutContext) {
        setLeadingBasedOnPageNumber(layoutContext.getArea().getPageNumber());
        return super.layout(layoutContext);
    }

    private void setLeadingBasedOnPageNumber(int pageNumber) {
        if (pageNumber == 1) {
            this.setProperty(Property.LEADING, new Leading(Leading.FIXED, 100));
        } else {
            this.setProperty(Property.LEADING, new Leading(Leading.FIXED, 50));
        }
    }

    @Override
    public IRenderer getNextRenderer() {
        return new ParagraphRenderer((Paragraph) modelElement);
    }
}

Note that the logic of determining the desired leading depending on the page number resides in VariableLeadingParagraphRenderer#setLeadingBasedOnPageNumber

You can then use the custom renderer as follows:

Document document = new Document(pdfDocument);

String line = "Hello! Welcome to iTextPdf";
for (int i = 0; i < 30; i++) {
    Paragraph element = new Paragraph();
    element.add(line + " " + i);
    element.setNextRenderer(new VariableLeadingParagraphRenderer(element));
    document.add(element);
}

Visual result. Page 1:

Page 2: