iText制作PDF，RaidoGroup

package test;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Phrase;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfFormField;
import com.itextpdf.text.pdf.PdfPCell;
import com.itextpdf.text.pdf.PdfPCellEvent;
import com.itextpdf.text.pdf.PdfPTable;
import com.itextpdf.text.pdf.PdfWriter;
import com.itextpdf.text.pdf.RadioCheckField;
public class RadioGroupMultiPage2 {
	 public static final String DEST = "E:\\RadioGroup.pdf";
	    public static void main(String[] args) throws DocumentException, IOException {
	        File file = new File(DEST);
	        file.getParentFile().mkdirs();
	        new RadioGroupMultiPage2().createPdf(DEST);
	    }
	    public void createPdf(String dest) throws IOException, DocumentException {
	        Document document = new Document();
	        PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(dest));
	        document.open();
	        PdfFormField radiogroup = PdfFormField.createRadioButton(writer, true);
	        radiogroup.setFieldName("answer");
	        PdfPTable table = new PdfPTable(2);
	        PdfPCell cell;
	        for (int i = 0; i < 25; i++) {
	            cell = new PdfPCell(new Phrase("Question " + i));
	            table.addCell(cell);
	            cell = new PdfPCell(new Phrase("Answer " + i));
	            table.addCell(cell);
	        }
	        for (int i = 0; i <25; i++) {
	            cell = new PdfPCell(new Phrase("Radio: " + i));
	            table.addCell(cell);
	            cell = new PdfPCell();
	            cell.setCellEvent(new MyCellField(writer, radiogroup, "answer" + i));
	            table.addCell(cell);
	        }
	        document.add(table);
	        writer.addAnnotation(radiogroup);
	        document.close();
	        System.out.println("===========:end");
	    }
	 
	    class MyCellField implements PdfPCellEvent {
	 
	        protected PdfWriter writer;
	        protected PdfFormField radiogroup;
	        protected String value;
	 
	        public MyCellField(PdfWriter writer, PdfFormField radiogroup, String value) {
	            this.writer = writer;
	            this.radiogroup = radiogroup;
	            this.value = value;
	        }
	 
	        public void cellLayout(PdfPCell cell, Rectangle position, PdfContentByte[] canvases) {
	            try {
	                RadioCheckField radio = new RadioCheckField(writer, position, null, value);
	                PdfFormField field = radio.getRadioField();
	                writer.addAnnotation(field);
	                //关键
	                radiogroup.addKid(field);
	            } catch (IOException ex) {
	                // do nothing
	            } catch (DocumentException ex) {
	                // do nothing
	            }
	        }
	    }
}