Organizing content in tables in Java

Create Quick Response Code in Java Organizing content in tables

iText s table functionality has evolved from a very low-level class in the early versions of iText to the twin classes Table and PdfTable in iText 0.30 (2000). These classes were useful, but they had some flaws. It was hard to fine-tune them due to design decisions made by the iText developers; that is, by me. Developers wanted to define how to split the table upon a page break, to control the way borders are drawn, and so on. The PdfPTable class, introduced by the codeveloper of iText, Paulo Soares, solved this problem. The Table and PdfTable classes were removed in iText 5 (2009). So were SimpleTable and SimpleCell, two other table classes discussed in the first edition of iText in Action. Only PdfPTable and PdfPCell remain. They will be discussed in this chapter.

Suppose that you need to create a simple table that looks like figure 4.1. The code to generate this kind of table is pretty simple.

PdfPTable table = new PdfPTable(3); Creates table with 3 columns PdfPCell cell; cell = new PdfPCell(new Phrase("Cell with colspan 3")); Adds cell with cell.setColspan(3); colspan 3 table.addCell(cell); cell = new PdfPCell(new Phrase("Cell with rowspan 2")); Adds cell with cell.setRowspan(2); rowspan 2 table.addCell(cell); table.addCell("row 1; cell 1"); table.addCell("row 1; cell 2"); Adds remaining table.addCell("row 2; cell 1"); cells table.addCell("row 2; cell 2");

When you create a PdfPTable, you always need to pass the number of columns to the constructor. Creating a table with zero columns results in a RuntimeException. You can add different objects to a PdfPTable object using the addCell() method.

There s a PdfPRow object in the com.itextpdf.text.pdf package, but you aren t supposed to address it directly. iText uses this class internally to store the cells that belong to the same row.

In listing 4.1, the table has three columns B. After adding the first cell with column span 3 C, the first row is full. The next cell is added to a second row that is created automatically by iText. This cell has to span 2 rows D, so a third row is created, of which the first cell is reserved. Four more cells are then added E; the first pair completes the second row; the second pair completes the third row.

When you add a PdfPTable to a Document, only complete rows are added. If you have a table with three columns and your final row has only two cells, the row won t be added unless you use the method PdfPTable. completeRow().

You don t have to worry about creating rows; iText creates them for you. Just make sure you re adding the correct number of cells.

We ll talk about cells and cell properties such as text alignment, spacing, and borders in the next section. First, let s take a look at the properties of the table: the width of the table and its columns, the spacing before and after the table, and the alignment of the table. The default width of a table is 80 percent of the available width. Let s do the math for the table created by listing 4.1. The width of the page is 595 pt minus the margins, which are 36 pt. Eighty percent of this width is (595 (2 * 36)) * 0.80, which amounts to 418.4 pt.

Each PdfPTable keeps two values for the width:

widthPercentage A percentage of the available width totalWidth The absolute width expressed in user space units

When you add a PdfPTable to a Document, iText looks at one of these values, ignoring the other, depending on the value of lockedWidth. If this value is true, the table will have a fixed width, as defined by the totalWidth variable. By default, the value is false, and the exact width of the table will depend on the width available on the page or the width of the ColumnText object to which it s added. The default width of the columns is equal to the width of the table divided by the number of columns.

FAQ Is it possible to have the column width change dynamically based on the content of the cells PDF isn t HTML, and a PdfPTable is completely different from an HTML table rendered in a browser; iText can t calculate column widths based on the content of the columns. The result would depend on too many design decisions and wouldn t always correspond to what a developer expects. It s better to have the developer define the widths.

You could say that each column has a relative width equal to 1. You can change this by defining new relative widths, or by setting absolute widths for the columns.