如何在iText 5中显示所见即所得字段？

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Font;
import com.itextpdf.text.FontFactory;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.AcroFields;
import com.itextpdf.text.pdf.BaseFont;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;
import com.itextpdf.text.pdf.TextField;

import java.io.FileOutputStream;
import java.io.IOException;

public class ITextExample {
    public static void main(String[] args) {
        try {
            // 读取现有的PDF文件
            PdfReader reader = new PdfReader("input.pdf");
            // 创建一个新的PDF文件
            PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("output.pdf"));
            // 获取AcroFields对象
            AcroFields form = stamper.getAcroFields();
            
            // 创建文本域字段
            TextField textField = TextField.createTextField(stamper.getWriter(), new Rectangle(100, 100, 200, 50), "text_field");
            textField.setFontSize(12);
            textField.setTextColor(BaseColor.BLACK);
            textField.setBorderStyle(PdfBorderDictionary.STYLE_SOLID);
            textField.setBorderColor(BaseColor.GRAY);
            textField.setFieldFlags(PdfFormField.FF_MULTILINE);
            // 设置文本域的默认值
            textField.setText("Default value");
            // 将字段添加到AcroFields对象
            form.setField("text_field", textField.getTextField());
            
            // 关闭PdfStamper对象
            stamper.close();
            // 关闭PdfReader对象
            reader.close();
            
            System.out.println("PDF created successfully.");
        } catch (IOException | DocumentException e) {
            e.printStackTrace();
        }
    }
}