如何计算itext 7中表格列的总数和小计？

Question

在itext 5中，可以使用单元格事件来计算表格列的小计。这怎么能在itext 7中完成？

把itext 5的例子可以在以下网址找到：http://developers.itextpdf.com/examples/tables/using-cell-events-add-special-content#2887-subtotal.java

Answer 1

目前的细胞事件的功能在iText7没有直接替代品。使用丰富的渲染机制可以实现期望的输出，该机制允许比事件更多地实现期望的输出。

我只会提供一种可能的方法来实现页面上的小表的小计。总是很容易，因此我将它放在答案的范围之外。

对于初学者来说，我们需要负责计算类：

private static class SubtotalHandler { 
    private int subtotalSum; 

    public void reset() { 
     subtotalSum = 0; 
    } 

    public void add(int val) { 
     subtotalSum += val; 
    } 

    public int get() { 
     return subtotalSum; 
    } 
} 

生成表中的代码本身看起来像这样：

同价位细胞

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); 

渲染器只是告诉已添加部分金额的小计处理程序：

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); 
    } 
} 

何时来s到页脚单元的渲染，对应的单元格询问量，并把它打印小计处理，事后重置大部处理程序：

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); 
    } 
} 

输出看起来是这样的：