在引用this示例时，我创建了一个用于页眉页脚和页码的程序。
但是在运行该程序时，它将引发BadElementException：Template不能为null。
以下是我的完整代码
import java.awt.Desktop;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import wt.query.QueryException;
import wt.util.WTException;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Element;
import com.itextpdf.text.Image;
import com.itextpdf.text.PageSize;
import com.itextpdf.text.Phrase;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.ColumnText;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfPCell;
import com.itextpdf.text.pdf.PdfPTable;
import com.itextpdf.text.pdf.PdfPageEventHelper;
import com.itextpdf.text.pdf.PdfTemplate;
import com.itextpdf.text.pdf.PdfWriter;
import com.itextpdf.text.pdf.draw.LineSeparator;
public class TestHF2 {
public static final String RESULT="Pagenumber.pdf";
public class HeaderFooter extends PdfPageEventHelper
{
String header;
PdfTemplate total;
public void setHeader(String header)
{
this.header=header;
}
public void openDocument(PdfWriter writer,Document document)
{
total=writer.getDirectContent().createTemplate(30, 16);
}
public void onEndPage(PdfWriter writer,Document document)
{
PdfPTable table=new PdfPTable(3);
try {
table.setWidths(new int[]{24,24,2});
table.setTotalWidth(527);
table.setLockedWidth(true);
table.getDefaultCell().setFixedHeight(20);
table.getDefaultCell().setBorder(Rectangle.BOTTOM);
table.addCell(header);
table.getDefaultCell().setHorizontalAlignment(Element.ALIGN_LEFT);
table.addCell(String.format("Page %d of", writer.getPageNumber()));
PdfPCell cell=new PdfPCell(Image.getInstance(total));
cell.setBorder(Rectangle.BOTTOM);
table.addCell(cell);
table.writeSelectedRows(0, -1, 34, 803, writer.getDirectContent());
} catch (DocumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void onCloseDocument(PdfWriter writer,Document document)
{
ColumnText.showTextAligned(total, Element.ALIGN_LEFT, new Phrase(String.valueOf(writer.getPageNumber()-1)), 2, 2, 0);
}
@SuppressWarnings("unchecked")
public void createPDF() throws QueryException, WTException, DocumentException, IOException
{
String PartNO="GT024";
List L=winpar.start(PartNO);
List M=child.start1(PartNO);
Iterator it = L.iterator();
Iterator its = M.iterator();
Document document=new Document(PageSize.A4,36,36,54,36);
PdfWriter writer=PdfWriter.getInstance(document, new FileOutputStream(RESULT));
HeaderFooter event=new HeaderFooter();
writer.setPageEvent(event);
document.open();
@SuppressWarnings("unused")
PdfContentByte contentByte=writer.getDirectContent();
PdfPTable table=new PdfPTable(4);
table.setWidthPercentage(100);
table.getDefaultCell().setBorder(Rectangle.NO_BORDER);
table.getDefaultCell().setBorder(Rectangle.BOTTOM);
table.getDefaultCell().setHorizontalAlignment(Element.ALIGN_LEFT);
table.getDefaultCell().setFixedHeight(20);
LineSeparator ls=new LineSeparator();
document.add(ls);
table.addCell("Name");
table.addCell("Number");
table.addCell("State");
table.addCell("Container");
LineSeparator ls1=new LineSeparator();
document.add(ls1);
while (it.hasNext()) {
insertCell(table, it.next().toString(), Element.ALIGN_LEFT, 1);
insertCell(table, it.next().toString(), Element.ALIGN_LEFT, 1);
insertCell(table, it.next().toString(), Element.ALIGN_LEFT, 1);
insertCell(table, it.next().toString(), Element.ALIGN_LEFT, 1);
}
while (its.hasNext()) {
insertCell(table, its.next().toString() , Element.ALIGN_LEFT, 1);
insertCell(table, its.next().toString(), Element.ALIGN_LEFT, 1);
insertCell(table, its.next().toString(), Element.ALIGN_LEFT, 1);
insertCell(table, its.next().toString(), Element.ALIGN_LEFT, 1);
}
document.add(table);
document.close();
File file = new File("PageAndheader.pdf");
if (file.toString().endsWith(".pdf")) {
Runtime.getRuntime().exec("rundll32 url.dll,FileProtocolHandler " + file);
} else {
Desktop desktop = Desktop.getDesktop();
desktop.open(file);
}
}
}
private static void insertCell(PdfPTable table, String text, int align, int colspan) {
//create a new cell with the specified Text and Font
PdfPCell cell = new PdfPCell(new Phrase(text.trim()));
cell.setBorder(Rectangle.NO_BORDER);
//set the cell alignment
cell.setHorizontalAlignment(align);
//set the cell column span in case you want to merge two or more cells
cell.setColspan(colspan);
//in case there is no text and you wan to create an empty row
if (text.trim().equalsIgnoreCase("")) {
cell.setMinimumHeight(10f);
}
//add the call to the table
table.addCell(cell);
}
public static void main(String args[]) throws QueryException, DocumentException, WTException, IOException,ClassCastException, com.lowagie.text.DocumentException
{
TestHF2 ot=new TestHF2();
TestHF2.HeaderFooter obj=ot.new HeaderFooter();
obj.createPDF();
}
}
我得到这样的输出
`Query size ===8
child size is: 4
com.itextpdf.text.BadElementException: The template can not be null.
at com.itextpdf.text.ImgTemplate.<init>(ImgTemplate.java:74)
at com.itextpdf.text.Image.getInstance(Image.java:589)
at ext.gt.checkOut.TestHF2$HeaderFooter.onEndPage(TestHF2.java:61)
at com.itextpdf.text.pdf.PdfDocument.newPage(PdfDocument.java:858)
at com.itextpdf.text.pdf.PdfDocument.close(PdfDocument.java:793)
at com.itextpdf.text.Document.close(Document.java:416)
at ext.gt.checkOut.TestHF2$HeaderFooter.createPDF(TestHF2.java:118)
at ext.gt.checkOut.TestHF2.main(TestHF2.java:154)
Exception in thread "main" java.lang.NullPointerException
at com.itextpdf.text.pdf.ColumnText.showTextAligned(ColumnText.java:1189)
at com.itextpdf.text.pdf.ColumnText.showTextAligned(ColumnText.java:1251)
at ext.gt.checkOut.TestHF2$HeaderFooter.onCloseDocument(TestHF2.java:73)
at com.itextpdf.text.pdf.PdfDocument.close(PdfDocument.java:799)
at com.itextpdf.text.Document.close(Document.java:416)
at ext.gt.checkOut.TestHF2$HeaderFooter.createPDF(TestHF2.java:118)
at ext.gt.checkOut.TestHF2.main(TestHF2.java:154)
`
从这个类中，我已经将另外两个称为我的自定义类。但是我不知道为什么会得到BadElementException：模板不能为null。所以我在这里创建了一个模板，但是我不知道为什么会这样。
对不起，添加了我的程序的整个部分。我别无选择。感谢您阅读我的所有问题。我需要一些帮助
最佳答案
当执行onEndPage（）时，“ total”变量为null。