如何更改Android中每个PDF页面的标题

Question

I created pdf page using itext in android application,need to add header and footer for pdf page and need to change header in every page.

i did like for adding header and footer

public class HeaderAddFooter extends PdfPageEventHelper {

private Phrase footer;
private Phrase header;
private String patientName;
private String patientID;
Font headerFont = new Font(FontFamily.TIMES_ROMAN, 12, Font.NORMAL);
Font footerFont = new Font(FontFamily.TIMES_ROMAN, 12, Font.NORMAL);
Font TitleFont = new Font(FontFamily.COURIER, 14, Font.NORMAL);

/*
 * constructor
 */
public HeaderAddFooter(String name,String id) {
    super();

    header = new Phrase("***** Header *****");
    footer = new Phrase("**** Footer ****");
    patientName=name;
    patientID=id;
}


@Override
public void onStartPage(PdfWriter writer, Document document) {

    super.onStartPage(writer, document);


}

@Override
public void onEndPage(PdfWriter writer, Document document) {

    PdfContentByte cb = writer.getDirectContent();

    SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
   // Date date = new Date();
    Calendar cal = Calendar.getInstance();



  ColumnText.showTextAligned(cb, Element.ALIGN_LEFT, new Phrase("welcome",headerFont), 
            document.leftMargin()-1, document.top()+10, 0);

    ColumnText.showTextAligned(cb, Element.ALIGN_RIGHT, new Phrase("Name",headerFont), 
            document.right(), document.top()+15, 0);
    ColumnText.showTextAligned(cb, Element.ALIGN_RIGHT, new Phrase("Designation",headerFont), 
            document.right(), document.top()+1, 0);


    /*
     * Foooter
     */

    ColumnText.showTextAligned(cb, Element.ALIGN_MIDDLE, new Phrase("Page:"+String.format(" %d ", 
            writer.getPageNumber()),footerFont), 
            document.right() - 280 , document.bottom() - 10, 0);
    ColumnText.showTextAligned(cb, Element.ALIGN_MIDDLE, new Phrase(dateFormat.format(cal.getTime()),footerFont), 

            document.right() - 350 , document.bottom() - 25, 0);


}

}

now when add new values to header it showing like merge text both previous text and new header text. how can i change header dynamically for every page

Answer 1

When asked how he adds new values to header, the OP clarified in a comment that he does so by

sending values to constructor for each page

This seems to indicate that he every once in a while creates a new HeaderAddFooter instance and forwards it to the PdfWriter method setPageEvent .

Unfortunately the OP was not able or willing to provide more code. Thus, let's assume his code looks like this

Document document = new Document();
PdfWriter writer = PdfWriter.getInstance(document, ...);
document.open();

for (int page = ...)
{
    String nameForPage = ...
    String idForPage = ...
    writer.setPageEvent(new HeaderAddFooter(nameForPage, idForPage));

    ... add content for page ...
    document.newPage();
}

document.close();

This, unfortunately, does not work as expected because PdfWriter.setPageEvent is a bit misnamed (and also mis-documented in the Javadocs): It is not a true setter but instead more like an adder:

public void setPageEvent(final PdfPageEvent event) {
    if (event == null) this.pageEvent = null;
    else if (this.pageEvent == null) this.pageEvent = event;
    else if (this.pageEvent instanceof PdfPageEventForwarder) ((PdfPageEventForwarder)this.pageEvent).addPageEvent(event);
    else {
        PdfPageEventForwarder forward = new PdfPageEventForwarder();
        forward.addPageEvent(this.pageEvent);
        forward.addPageEvent(event);
        this.pageEvent = forward;
    }
}

Thus, the OP's assumed code does not replace the former page event listener by a new one but insteads adds to it.

There are two ways to fix this:

• Either set only one HeaderAddFooter instance initially outside the loop and change the contents of its members inside the loop:

   Document document = new Document(); PdfWriter writer = PdfWriter.getInstance(document, ...); document.open(); HeaderAddFooter headerAddFooter = new HeaderAddFooter("", ""); writer.setPageEvent(headerAddFooter); for (int page = ...) { String nameForPage = ... String idForPage = ... headerAddFooter.patientName = nameForPage; headerAddFooter.patientID = idForPage; ... add content for page ... document.newPage(); } document.close(); 

  This most likely will require making those HeaderAddFooter member variables more visible. Alternatively setter methods may be added for them.

• Or make use of the special treatment of null in PdfWriter.setPageEvent :

   Document document = new Document(); PdfWriter writer = PdfWriter.getInstance(document, ...); document.open(); for (int page = ...) { String nameForPage = ... String idForPage = ... writer.setPageEvent(null); writer.setPageEvent(new HeaderAddFooter(nameForPage, idForPage)); ... add content for page ... document.newPage(); } document.close(); 

The first alternative (with the use of setter methods for cleaner code) is the more common variant.