java - 如何在开始时将标题设置为PDF以及如何设置居中对齐

Question

在这张图片中，我想使用库itextpdf(版本7.0.2)设置我的pdf标题，但结果是:

代码:

    String file = "C:/Users/User/Desktop/generator/Test.pdf";
    PdfDocument pdfDoc = new PdfDocument(new PdfWriter(file));
    Document doc = new Document(pdfDoc);
    float[] pointColumnWidths = {450, 200F};
    Table table = new Table(pointColumnWidths);

    Text text1 = new Text("BLABLA BLABLA");
    PdfFont font = PdfFontFactory.createFont(FontConstants.HELVETICA_BOLD);
    text1.setFont(font);
    text1.setFontSize(20);
    text1.setBackgroundColor(Color.BLUE, 170, 20, 170, 20);
    text1.setFontColor(Color.WHITE);
    Paragraph paragraph1 = new Paragraph();
    paragraph1.add(text1);
    doc.add(paragraph1);


    Cell c1 = new Cell();
    c1.add("BlaBla:");
    c1.setBorder(Border.NO_BORDER);
    c1.setTextAlignment(TextAlignment.LEFT);
    table.addCell(c1);


    Cell c2 = new Cell();
    String number = "45875454";
    c2.setBorder(Border.NO_BORDER);
    c2.add(number);
    c2.setTextAlignment(TextAlignment.LEFT);
    table.addCell(c2);

    Cell c3 = new Cell();
    c3.add("BlaBla:");
    c3.setBorder(Border.NO_BORDER);
    c3.setTextAlignment(TextAlignment.LEFT);
    table.addCell(c3);


    Cell c4 = new Cell();
    String date = "06.04.2020";
    c4.setBorder(Border.NO_BORDER);
    c4.add(date);
    c4.setTextAlignment(TextAlignment.LEFT);
    table.addCell(c4);

    Cell c5 = new Cell();
    c5.add("BlaBla:");
    c5.setBorder(Border.NO_BORDER);
    c5.setTextAlignment(TextAlignment.LEFT);
    table.addCell(c5);


    Cell c6 = new Cell();
    String index = "56";
    c6.setBorder(Border.NO_BORDER);
    c6.add(index);
    c6.setTextAlignment(TextAlignment.LEFT);
    table.addCell(c6);

    Cell c7 = new Cell();
    c7.add("BlaBla:");
    c7.setBorder(Border.NO_BORDER);
    c7.setTextAlignment(TextAlignment.LEFT);
    table.addCell(c7);


    Cell c8 = new Cell();
    String blaBla = "06.04.2020";
    c8.setBorder(Border.NO_BORDER);
    c8.add(blaBla);
    c8.setTextAlignment(TextAlignment.LEFT);
    table.addCell(c8);

    doc.add(table);

    doc.close();

Answer 1

import com.itextpdf.text.Document;
import com.itextpdf.text.Element;
import com.itextpdf.text.Phrase;
import com.itextpdf.text.pdf.ColumnText;
import com.itextpdf.text.pdf.PdfPageEventHelper;
import com.itextpdf.text.pdf.PdfWriter;

public class HeaderFooterPageEvent extends PdfPageEventHelper {

    public void onStartPage(PdfWriter writer, Document document) {
        ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_CENTER, new Phrase("Top Left"), 30, 800, 0);
        ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_CENTER, new Phrase("Top Right"), 550, 800, 0);
    }

    public void onEndPage(PdfWriter writer, Document document) {
        ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_CENTER, new Phrase("Bla Bla"), 110, 30, 0);
        ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_CENTER, new Phrase("page " + document.getPageNumber()), 550, 30, 0);
    }

}

iText 提供了 PdfPageEventHelper 类，该类具有在编写 PDF 时调用的不同事件方法。要添加页眉和页脚，我们需要创建一个扩展 PdfPageEventHelper 的类并重写 onStartPage 和 onEndPage 方法。使用 PdfWriter 注册此类。

创建事件类HeaderFooterPageEvent扩展PdfPageEventHelperPdfPageEventHelper 类对于 PDF 有不同的事件方法。它实现了PdfPageEvent接口(interface)。 PdfPageEventHelper的一些事件方法如下

onOpenDocument
onStartPage
onEndPage
onCloseDocument
onParagraph
onParagraphEnd