MovieHistory2.java in Java

Generate QR-Code in Java MovieHistory2.java

class HeaderFooter extends PdfPageEventHelper { Phrase[] header = new Phrase[2]; int pagenumber; public void onOpenDocument(PdfWriter writer, Document document) { header[0] = new Phrase("Movie history"); } public void on(PdfWriter writer, Document document, float paragraphPosition, Paragraph title) { header[1] = new Phrase(title.getContent()); pagenumber = 1; } public void onStartPage(PdfWriter writer, Document document) { pagenumber++; } public void onEndPage(PdfWriter writer, Document document) { Rectangle rect = writer.getBoxSize("art"); switch(writer.getPageNumber() % 2) { case 0: ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_RIGHT, header[0], rect.getRight(), rect.getTop(), 0); break; case 1:

ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_LEFT, header[1], rect.getLeft(), rect.getTop(), 0); break; } ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_CENTER, new Phrase( String.format("page %d", pagenumber)), (rect.getLeft() + rect.getRight()) / 2, rect.getBottom() - 18, 0); } }

There are no surprises in this code sample. You define two member variables:

header An array with two Phrase objects. One is set in onOpenDocument(), and it s valid for the full document. The other varies depending on the current chapter. It s set in the on() method. pagenumber A custom page number that is reset to 1 every time a new chapter starts. It s augmented in the onStartPage() method.

No content is added in the page event until a page has been completed. The header and footer are written to the direct content in the onEndPage() method. The parameters writer and document are to be used in the same way as done in section 5.2. Note that you ask the writer for the art box rectangle using the getBoxSize() method. You use this rectangle to position the header and the footer. This will only work if you ve defined that specific page boundary between steps 2 and 3 in the PDF creation process. Otherwise, the getBoxSize() method will return null. Why is it not advised to add content in the onStartPage() method You ll remember from section 5.2.4 that iText ignores newPage() calls when the current page is empty. This method is executed or ignored when you call it explicitly from your code, but it s also invoked implicitly from within iText on multiple occasions. It s important that it s ignored for empty pages; otherwise you d end up with plenty of unwanted new pages that are unintentionally left blank. If you add content in an onStartPage() method, there s always a risk of having unwanted pages. Consider it more safe to reserve the onEndPage() method for adding content.

In the next example, you ll put the page number in the header, and you ll add the total number of pages.

An example of a page X of Y header is shown in figure 5.12. Retrieving the value of X is easy. You have access to the PdfWriter object in the onEndPage() method, so you can get the page number with getPageNumber(). But how can you retrieve the value for Y There s no way of knowing the total number of pages when the headers for the first pages are written. You only know the value of Y for sure when iText has finished writing the last page.

There are two ways to solve this problem. One solution will be discussed in the next chapter. It involves creating the PDF in two passes. You add the content in the first pass and the header or footer in a second pass. The other solution involves a PdfTemplate object and page events. When we discussed form XObjects in section 3.4.2, I explained that iText only writes a PdfTemplate to the OutputStream when you explicitly use the releaseTemplate() method. Otherwise the object is kept in memory until you close the Document. This opens possibilities: you can add a template to page 1, and wait until the final page to write content to this template. Even if the content stream of the first page has already been sent to the OutputStream, the content added to the template afterwards will still be shown on the first page.