iTextsharp PdfPTable写行

Question

为什么我不能将包含PdfPTable的PdfFormField写到现有的PDF中？iTextSharp告诉我

在这种情况下不受支持。使用PdfStamper.addAnnotation()。

Private Sub RR(PdfFileName As String)
    Dim reader As New PdfReader(PdfFileName)
    Dim RandomFileName As String = System.IO.Path.GetRandomFileName
    Dim OutputPdf As String = System.IO.Path.GetDirectoryName(PdfFileName) & "\" & System.IO.Path.GetFileNameWithoutExtension(RandomFileName) & ".pdf"

    Dim stamper As New PdfStamper(reader, New FileStream(OutputPdf, FileMode.Create))
    Dim table As New PdfPTable(1)
    Dim PageMargin As Single = 20
    Dim tbCell As New PdfPCell()

    table.TotalWidth = (reader.GetPageSize(1).Right - reader.GetPageSize(1).Left) - 20
    Dim PDfFormField As PdfFormField = CreateTextField(stamper.Writer, "TestField", 0, 0)
    tbCell = New PdfPCell With {.CellEvent = New iTextSharp.text.pdf.events.FieldPositioningEvents(stamper.Writer, PDfFormField), .MinimumHeight = 10, .BorderWidth = 0.1}

    With table
        .AddCell(tbCell)
    End With

    table.WriteSelectedRows(0, -1, PageMargin, Bottom + table.TotalHeight + PageMargin, stamper.GetOverContent(1))

    stamper.Close()
    reader.Close()

End Sub

Answer 1

问题

现在的iTextSharp类FieldPositioningEvents只有在结合使用基本PdfWriter和PdfDocument实例从头创建新的PDF时才能使用，因为它使用了在冲压上下文中不支持的writer.addAnnotation(field) / fieldWriter.addAnnotation(cellField)调用。

解决方案

要解决这个限制，只需创建您自己的单元格事件侦听器，它使用addAnnotation重载并在PdfStamper中显示一个页码。

(不幸的是，在本世纪我还没有做过任何VB编码；不过，我希望C#中的示例也能有所帮助。)

例如，下面是从原始FieldPositioningEvents代码派生的这样一个事件侦听器，但仅被缩减为单元事件，并适合于在PdfStamper中使用

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);
    }
} 

它可以以类似OP的原始代码的方式使用：

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();