java 如何调整 PdfPTable 的大小以适合页面？

How to resize a PdfPTable to fit the page?

提问by Jannis Alexakis

I am generating a document, like in the following code, except ofcourse the contents of the table, which are varying. What I need to do is make sure that this table never exceeds one page in size, regardless of the amount of content in the cells. Is there a way to do it ?

我正在生成一个文档，就像下面的代码一样，当然表的内容除外，它们是变化的。我需要做的是确保该表格的大小永远不会超过一页，无论单元格中的内容量如何。有没有办法做到这一点？

import com.itextpdf.text.Phrase;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.PageSize;
import com.itextpdf.text.pdf.PdfPCell;
import com.itextpdf.text.pdf.PdfPTable;
import java.awt.Desktop;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;


public void createTemplate() throws DocumentException, FileNotFoundException, IOException{
        String TARGET = System.getProperty("user.home")+"\temp.pdf";

        Document document = new Document(PageSize.A4);
        PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(TARGET));
        document.open();

    PdfPTable table = new PdfPTable(7);         

    for (int i = 0; i < 105; i++) {
        Phrase p = new Phrase("some text");
        PdfPCell cell = new PdfPCell();
        cell.addElement(p);
        table.addCell(cell);            
    }

    table.setTotalWidth(PageSize.A4.getWidth()-10);
    table.setLockedWidth(true);
    PdfContentByte canvas = writer.getDirectContent();
    PdfTemplate template = canvas.createTemplate(table.getTotalWidth(),table.getTotalHeight());
    table.writeSelectedRows(0, -1, 0, PageSize.A4.getHeight(), template);
    Image img = Image.getInstance(template);
    img.scaleToFit(PageSize.A4.getWidth(), PageSize.A4.getHeight());
    img.setAbsolutePosition(0, PageSize.A4.getHeight());
    document.add(img);
    document.close();

    Desktop desktop = Desktop.getDesktop();
    File file = new File(TARGET);
    desktop.open(file);    }

Edit: @Bruno Lowagie. The hint with the template wrapped in an image sounds just right to me, and I changed the code according, but all I get now is an empty PDF. Am I doing something wrong, or is this the wrong approach alltogether?

编辑：@Bruno Lowagie。包含在图像中的模板提示对我来说听起来恰到好处，我相应地更改了代码，但现在我得到的只是一个空的 PDF。我做错了什么，还是这完全是错误的方法？

回答by Bruno Lowagie

If you want a table to fit a page, you should create the table before even thinking about page size and ask the table for its height as is done in the TableHeightexample. Note that the getTotalHeight()method returns 0 unless you define the width of the table. This can be done like this:

如果您希望表格适合页面，您应该在考虑页面大小之前创建表格并询问表格的高度，如TableHeight示例中所做的那样。请注意，getTotalHeight()除非您定义表格的宽度，否则该方法返回 0。这可以像这样完成：

    table.setTotalWidth(width);
    table.setLockedWidth(true);

Now you can create a Documentwith size Rectangle(0, 0, width + margin * 2, getTotalHeight() + margin * 2)and the table should fit the document exactly when you add it with the writeSelectedRows()method.

现在您可以创建一个Document大小，Rectangle(0, 0, width + margin * 2, getTotalHeight() + margin * 2)并且当您使用该writeSelectedRows()方法添加表格时，表格应该完全适合文档。

If you don't want a custom page size, then you need to create a PdfTemplatewith the size of the table and add the table to this template object. Then wrap the template object in an Imageand use scaleToFit()to size the table down.

如果您不想要自定义页面大小，那么您需要创建一个PdfTemplate具有表格大小的表格并将表格添加到此模板对象中。然后将模板对象包装在一个中Image并用于scaleToFit()缩小表格的大小。

public static void main(String[] args) throws DocumentException, FileNotFoundException, IOException {
    String TARGET = "temp.pdf";
    Document document = new Document(PageSize.A4);
    PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(TARGET));
    document.open();


    PdfPTable table = new PdfPTable(7);         

    for (int i = 0; i < 700; i++) {
        Phrase p = new Phrase("some text");
        PdfPCell cell = new PdfPCell();
        cell.addElement(p);
        table.addCell(cell);            
    }

    table.setTotalWidth(PageSize.A4.getWidth());
    table.setLockedWidth(true);
    PdfContentByte canvas = writer.getDirectContent();
    PdfTemplate template = canvas.createTemplate(table.getTotalWidth(), table.getTotalHeight());
    table.writeSelectedRows(0, -1, 0, table.getTotalHeight(), template);
    Image img = Image.getInstance(template);
    img.scaleToFit(PageSize.A4.getWidth(), PageSize.A4.getHeight());
    img.setAbsolutePosition(0, (PageSize.A4.getHeight() - table.getTotalHeight()) / 2);
    document.add(img);
    document.close();
}