Header, footer and large tables with iTextSharp

问题

I've added an header and a footer on my document by PdfPageEventHelper.

The document has several "large" tables populated at runtime.

I've tried to add those tables simply by "documen.Add(table)", but my header and my footer results overwritten.

I've already tried both methods to add the tables (WriteSelectedRows and document.Add(myPdfPtable).

Here is the code of the PageEventHelper:

private class MyPageEventHandler : PdfPageEventHelper
{
        public iTextSharp.text.Image ImageHeader { get; set; }
        public iTextSharp.text.Image ImageFooter { get; set; }

        public override void OnEndPage(PdfWriter writer, Document document)
        {
            var fontintestazione = FontFactory.GetFont("Verdana", 10, Font.BOLD, BaseColor.LIGHT_GRAY);
            var fontRight = FontFactory.GetFont("Verdana", 8, Font.BOLD, BaseColor.WHITE);
            var fontFooter = FontFactory.GetFont("Verdana", 6, Font.NORMAL, BaseColor.BLUE);
            float cellHeight = document.TopMargin;
            Rectangle page = document.PageSize;
            PdfPTable head = new PdfPTable(3);
            head.TotalWidth = page.Width;

            PdfPCell c = new PdfPCell(ImageHeader, true);
            c.HorizontalAlignment = Element.ALIGN_LEFT;
            c.FixedHeight = cellHeight;
            c.Border = PdfPCell.NO_BORDER;
            head.AddCell(c);
             c = new PdfPCell(new Phrase("somePhrase", fontintestazione));
            c.Border = PdfPCell.NO_BORDER;
            head.AddCell(c);
            c = new PdfPCell(new Phrase("someTextBlah", fontRight));
            c.Border = PdfPCell.NO_BORDER;
            c.HorizontalAlignment = 1;
            c.BackgroundColor = new BaseColor(70, 130, 180);
            head.AddCell(c);
            head.WriteSelectedRows(0, -1, 10, page.Height - cellHeight + head.TotalHeight -30, writer.DirectContent);

            PdfPTable footer = new PdfPTable(2);
            footer.TotalWidth = 316f;
            float[] cfWidths = new float[] { 2f, 1f };
            footer.SetWidths(cfWidths);
            PdfPCell cf = new PdfPCell(ImageFooter, true);
            cf.HorizontalAlignment = Element.ALIGN_RIGHT;
            cf.FixedHeight = cellHeight;
            cf.Border = PdfPCell.NO_BORDER;
            footer.AddCell(cf);
            cf = new PdfPCell(new Phrase("someEndingText", fontFooter));
            cf.HorizontalAlignment = Element.ALIGN_LEFT;
            cf.Border = PdfPCell.NO_BORDER;
            footer.AddCell(cf);
            footer.WriteSelectedRows(0, -1, 10, 50, writer.DirectContent);
        }

On my page, i simply do:

var document = new Document(PageSize.A4);

                var output = new MemoryStream();
                var writer = PdfWriter.GetInstance(document, output);
                iTextSharp.text.Image imageHeader = iTextSharp.text.Image.GetInstance(Server.MapPath("/images/header.ong"));
                iTextSharp.text.Image imageFooter = iTextSharp.text.Image.GetInstance(Server.MapPath("/images/footer.png"));
                MyPageEventHandler eve = new MyPageEventHandler
                {
                    ImageHeader = imageHeader ,
                    ImageFooter = imageFooter
                };
                writer.PageEvent = eve;
                document.Open();
//adding a table
PdfPTable cvTable = new PdfPtable(3);
cvTable.TotalWidth = document.PageSize.Width;
PdfPCell hCell = new PdfPCell(new Phrase("Jobs By User", aCustomFont));
cvTable.AddCell(hCell);
for(int i = 0; i < myTable.Records.Count; i++)
{
    PdfPCell idCell = new PdfPCell(new Phrase(myTable.Records[i]._id, aFont));
    cvTable.Add(idCell);
    //same stuff for other fields of table
}
//first attempt.... failed:
document.Add(cvTable) //<- header and footer are overwritten by table
//second attempt..... failed too...
cvTable.WriteSelectedRows(0, -1, 10, myPoisition, writer.DirectContent);
//kind of fail...:
//the table is large and need more pages. It is trunked on the first page and overwrite
//the footer.

回答1:

In your OnEndPage method you have this line:

head.WriteSelectedRows(0, -1, 10, page.Height - cellHeight + head.TotalHeight - 30, writer.DirectContent);

That code correctly calculates where to put content based on the page's height and top margin but also includes a magical 30 in there which is causing the header to be drawn on top of the table. Change it to this and your header will be fine.

head.WriteSelectedRows(0, -1, 10, page.Height - cellHeight + head.TotalHeight, writer.DirectContent);

I'm guessing that that 30 is trying to include some padding between your header and the table itself. What I would recommend is actually changing the document's margins themselves in the main code:

document.SetMargins(document.LeftMargin, document.RightMargin, document.TopMargin + 30, document.BottomMargin);

And then accounting for that in the OnEndPage method:

float cellHeight = document.TopMargin - 30;

Your footer code doesn't actually account for the bottom margin and just draws it at 50 so this will always overlap. The quick fix would be to change it to:

footer.WriteSelectedRows(0, -1, 10, footer.TotalHeight, writer.DirectContent);

This will at least get the footer bottom-aligned. If you want some more padding like above just adjust the document margins again:

document.SetMargins(document.LeftMargin, document.RightMargin, document.TopMargin + 30, document.BottomMargin + 30);

来源：https://stackoverflow.com/questions/9864525/header-footer-and-large-tables-with-itextsharp