iTextSharp: How to find the first and second row height in a table?

问题

I want to get the first and second column height to know if I need to call document.NewPage() or not. But, I can't find a way to do this without adding the table to the document.

Example:

PdfPRow firstRow = new PdfPRow(cells1.ToArray());
table.Rows.Add(firstRow);
PdfPRow secondRow = new PdfPRow(cells2.ToArray());
table.Rows.Add(secondRow);

float h1 = table.GetRowHeight(0), h2 = table.GetRowHeight(1);

if (currentY - h1 - h2 < 30) document.NewPage();

document.Add(table);

回答1:

See my answer here. Basically, you can't know the dimensions of a table until it renders. However, you can render the table to a document that you just throw away and then re-render it later.

回答2:

Interesting question, so +1. And already marked as answered, but...

"But, I can't find a way to do this without adding the table to the document."

It is possible. Wrap the PdfPTable in a ColumnText object and take advantage of the ColumnText.Go() overload to get the total height of any arbitrary/number of rows you want without adding the PdfPTable to the Document. Here's a simple helper method:

public static float TotalRowHeights(
  Document document, PdfContentByte content, 
  PdfPTable table, params int[] wantedRows) 
{
  float height = 0f;
  ColumnText ct = new ColumnText(content);
// respect current Document.PageSize    
  ct.SetSimpleColumn(
    document.Left, document.Bottom, 
    document.Right, document.Top
  );
  ct.AddElement(table);
// **simulate** adding the PdfPTable to calculate total height
  ct.Go(true);
  foreach (int i in wantedRows) {
    height += table.GetRowHeight(i);
  }
  return height;
}

And a simple use case tested with 5.2.0.0:

using (Document document = new Document()) {
  PdfWriter writer = PdfWriter.GetInstance(document, STREAM);
  document.Open();
  PdfPTable table = new PdfPTable(4);
  for (int i = 1; i < 20; ++i) {
    table.AddCell(i.ToString());
  }
  int[] wantedRows = {0, 2, 3};
  document.Add(new Paragraph(string.Format(
    "Simulated table height: {0}",
    TotalRowHeights(document, writer.DirectContent, table, wantedRows)
  )));
// uncomment block below to verify correct height is being calculated
/* 
  document.Add(new Paragraph("Add the PdfPTable"));
  document.Add(table);
  float totalHeight = 0f;
  foreach (int i in wantedRows) {
    totalHeight += table.GetRowHeight(i);
  }
  document.Add(new Paragraph(string.Format(
    "Height after adding table: {0}", totalHeight
  )));
*/
  document.Add(new Paragraph("Test paragraph"));
}

In the use case rows 1, 3, and 4 are used, but only to demonstrate any combination/number of rows will work.

回答3:

Unless you set the width of the table, table.GetRowHeight(0) will always return zero.

// added
table.TotalWidth = 400f;     
//
PdfPRow firstRow = new PdfPRow(cells1.ToArray());

table.Rows.Add(firstRow);
PdfPRow secondRow = new PdfPRow(cells2.ToArray());
table.Rows.Add(secondRow);

float h1 = table.GetRowHeight(0), h2 = table.GetRowHeight(1);

if (currentY - h1 - h2 < 30) document.NewPage();

document.Add(table);

回答4:

There is another way to do this: Create the table at first.

    this.table = new PdfPTable(relativeColumnWidths);
    this.table.SetTotalWidth(absoluteColumnWidths);
    this.rowCells.Clear();

You may now fill the List with table cells:

    Paragraph pText = new Paragraph(text, this.font);
    PdfPCell cell = new PdfPCell(pText);
    this.rowCells.Add(cell);

When you are ready to create the new row:

    PdfPRow row = new PdfPRow(this.rowCells.ToArray());
    this.table.Rows.Add(row);

This is nothing special. But if you now set the table width again, you are able to calculate the row height properly:

    this.table.SetTotalWidth(this.table.AbsoluteWidths);
    this.rowCells.Clear();
    float newRowsHeight = this.table.GetRowHeight(this.table.Rows.Count - 1);

If the row is not fitting your conditions you can simply remove it from the rows collection of the table. The total height of the table will be calculated properly also.

来源：https://stackoverflow.com/questions/9685337/itextsharp-how-to-find-the-first-and-second-row-height-in-a-table

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