How to calculate total and subtotal of a table column in itext 7? - subtotal

Question

In itext 5, it can be used cell events to compute a subtotal of a table column. How can this be done in itext 7?
The itext 5 example can be found in this URL: http://developers.itextpdf.com/examples/tables/using-cell-events-add-special-content#2887-subtotal.java

Answer 1

There is currently no direct alternative of cell event functionality in iText7.
Howerver, the desired output can be achieved using rich rendering mechanism which allows a lot more than just events.
I will provide just one of the possible ways to implement a subtotal of table on the page. Total is easy and thus I'm leaving it out of the scope of the answer.
For the starters, we will need a class responsible for calculations:
private static class SubtotalHandler {
private int subtotalSum;
public void reset() {
subtotalSum = 0;
}
public void add(int val) {
subtotalSum += val;
}
public int get() {
return subtotalSum;
}
}
The code for generating the table itself will look like this:
Table table = new Table(UnitValue.createPercentArray(new float[] {1, 1})).setWidth(400);
table.setHorizontalAlignment(HorizontalAlignment.CENTER);
// Create our calculating class instance
SubtotalHandler handler = new SubtotalHandler();
for (int i = 0; i < 200; i++) {
table.addCell(new Cell().add(String.valueOf(i + 1)));
int price = 10;
Cell priceCell = new Cell().add(String.valueOf(price));
// Note that we set a custom renderer that will interact with our handler
priceCell.setNextRenderer(new SubtotalHandlerAwareCellRenderer(priceCell, handler, price));
table.addCell(priceCell);
}
table.addFooterCell(new Cell().add("Subtotal"));
Cell subtotalCell = new Cell();
// We create a custom renderer for the subtotal value itself as well because the text of the cell will depend on the state of the subtotal handler
subtotalCell.setNextRenderer(new SubtotalCellRenderer(subtotalCell, handler));
table.addFooterCell(subtotalCell);
Renderers of cells with price just tell the subtotal handler that some amount has been added:
private static class SubtotalHandlerAwareCellRenderer extends CellRenderer {
private SubtotalHandler subtotalHandler;
private int price;
public SubtotalHandlerAwareCellRenderer(Cell modelElement, SubtotalHandler subtotalHandler, int price) {
super(modelElement);
this.subtotalHandler = subtotalHandler;
this.price = price;
}
#Override
public void draw(DrawContext drawContext) {
super.draw(drawContext);
subtotalHandler.add(price);
}
#Override
public IRenderer getNextRenderer() {
return new SubtotalHandlerAwareCellRenderer((Cell) modelElement, subtotalHandler, price);
}
}
When it comes to the rendering of the footer cell, the corresponding cell asks the subtotal handler about the amount and prints it, and resets the subtotal handler afterwards:
private static class SubtotalCellRenderer extends CellRenderer {
private SubtotalHandler subtotalHandler;
public SubtotalCellRenderer(Cell modelElement, SubtotalHandler subtotalHandler) {
super(modelElement);
this.subtotalHandler = subtotalHandler;
}
#Override
public void draw(DrawContext drawContext) {
super.draw(drawContext);
new Canvas(drawContext.getCanvas(), drawContext.getDocument(), occupiedArea.getBBox()).
showTextAligned(String.valueOf(subtotalHandler.get()), occupiedArea.getBBox().getX() + 3,
occupiedArea.getBBox().getY() + 3, TextAlignment.LEFT);
subtotalHandler.reset();
}
#Override
public IRenderer getNextRenderer() {
return new SubtotalCellRenderer((Cell) modelElement, subtotalHandler);
}
}
The output looks like this: