iTextsharp PdfPTable writeselectedrows

Question

为什么我不能将包含PdfPTable的{​​{1}}写入现有PDF？ iTextSharp告诉我

  

在此上下文中不受支持。使用PdfFormField。

PdfStamper.addAnnotation()

Answer 1

问题

iTextSharp类FieldPositioningEvents只能在将基础PdfWriter与PdfDocument实例结合使用时从头开始创建新PDF，因为它使用writer.addAnnotation(field) / fieldWriter.addAnnotation(cellField)调用在标记上下文中不受支持。

解决方案

要解决此限制，只需创建自己的单元格事件侦听器，该侦听器使用addAnnotation重载，并在PdfStamper中显示页码。

（不幸的是，我在本世纪尚未完成任何VB编码;但我希望，C＃中的示例也可以提供帮助。）

E.g。以下是从原始FieldPositioningEvents代码派生的事件监听器，但仅限于单元格事件并适用于PdfStamper：

public class StampingFieldPositioningEvents : IPdfPCellEvent
{
    /** Keeps the form field that is to be positioned in a cellLayout event. */
    protected PdfFormField cellField = null;

    /** The PdfStamper to use when a field has to added in a cell event. */
    protected PdfStamper fieldStamper = null;

    /** Some extra padding that will be taken into account when defining the widget. */
    public float padding;

    /** The page on which the field is added */
    int fieldPage = 0;

    /** Creates a new event. This constructor will be used if you need to position fields with a Cell Event. */
    public StampingFieldPositioningEvents(PdfStamper stamper, PdfFormField field, int page)
    {
        this.cellField = field;
        this.fieldStamper = stamper;
        this.fieldPage = page;
    }

    /** Creates a new event. This constructor will be used if you need to position fields with a Cell Event. */
    public StampingFieldPositioningEvents(PdfStamper stamper, String text, int page)
    {
        this.fieldStamper = stamper;
        TextField tf = new TextField(stamper.Writer, new Rectangle(0, 0), text);
        tf.FontSize = 14;
        cellField = tf.GetTextField();
        this.fieldPage = page;
    }

    /** The padding to set. */
    virtual public float Padding
    {
        set
        {
            padding = value;
        }
        get
        {
            return padding;
        }
    }

    /** IPdfPCellEvent implementation */
    virtual public void CellLayout(PdfPCell cell, Rectangle rect, PdfContentByte[] canvases)
    {
        cellField.Put(PdfName.RECT, new PdfRectangle(rect.GetLeft(padding), rect.GetBottom(padding), rect.GetRight(padding), rect.GetTop(padding)));
        fieldStamper.AddAnnotation(cellField, fieldPage);
    }
} 

它的使用方式类似于OP的原始代码：

PdfReader reader = new PdfReader(SOURCE);
PdfStamper stamper = new PdfStamper(reader, new FileStream(DESTINATION, FileMode.Create));

int pageMargin = 20;
PdfPTable table = new PdfPTable(1);
table.TotalWidth = reader.GetPageSize(1).Width - 40;

PdfFormField formField = PdfFormField.CreateTextField(stamper.Writer, false, false, 50);
formField.SetWidget(new Rectangle(0, 0), null);
formField.FieldName = "TestField";
PdfPCell tbCell = new PdfPCell
{
    CellEvent = new StampingFieldPositioningEvents(stamper, formField, 1),
    MinimumHeight = 10,
    BorderWidth = 0.1f
};

table.AddCell(tbCell);

table.WriteSelectedRows(0, -1, reader.GetPageSize(1).Left + pageMargin, reader.GetPageSize(1).Bottom + table.TotalHeight + pageMargin, stamper.GetOverContent(1));

stamper.Close();
reader.Close();