java - 在 itext7 中更灵活地绘制自定义表格边框

Question

之前我问过一个关于绘制自定义表格边框的问题:Draw custom borders for table spanning across more than one page in itext7

并且提供了一种绘制自定义边框的方法，但它不允许影响完整的行或列线(例如稍微倾斜)，因为单元格边框是为每个单元格单独绘制的。

我想为表格边框添加一些随机性，如下面的屏幕截图所示:

这是我的代码，适用于适合单个页面的表格，但如果表格跨越多个页面，则代码不再起作用:

PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
        Document doc = new Document(pdfDoc);
        doc.add(new Paragraph("Table event"));
        Table table = new Table(UnitValue.createPercentArray(3)).useAllAvailableWidth();
        table.setNextRenderer(new DottedLineTableRenderer(table, new Table.RowRange(0, 0)));
        String s ="";
        for(int i=0;i<35;i++){
        s+="\nTest";
         }
        table.addCell(new Cell().add(new Paragraph(s)).setBorder(Border.NO_BORDER));
        table.addCell(new Cell().add(new Paragraph("A2")).setBorder(Border.NO_BORDER));
        table.addCell(new Cell().add(new Paragraph("A3")).setBorder(Border.NO_BORDER));


        doc.add(table);


        doc.close();

private class DottedLineTableRenderer extends TableRenderer {
    public DottedLineTableRenderer(Table modelElement, Table.RowRange rowRange) {
        super(modelElement, rowRange);
    }

    @Override
    public void drawChildren(DrawContext drawContext) {
        super.drawChildren(drawContext);
        PdfCanvas canvas = drawContext.getCanvas();
        int maxLineTo = 5;
        int minLineTo = 2;
        int lineToHorizontalLine = (int)(Math.random() * maxLineTo) + minLineTo;

        int maxSkewHor = 5;
        int minSkewHor = 2;
        int skewHorizontalLine = (int)(Math.random() * maxSkewHor) + minSkewHor;

        int maxVerticalLine = 5;
        int minVerticalLine = 2;
        int lineToVerticalLine = (int)(Math.random() * maxVerticalLine) + minVerticalLine;


        canvas.setLineWidth(2).setStrokeColor(new DeviceRgb(222, 27, 27));

        // first horizontal line
        CellRenderer[] cellRenderers = rows.get(0);
        canvas.moveTo(cellRenderers[0].getOccupiedArea().getBBox().getLeft()-lineToHorizontalLine,
                cellRenderers[0].getOccupiedArea().getBBox().getTop());
        canvas.lineTo(cellRenderers[cellRenderers.length - 1].getOccupiedArea().getBBox().getRight()+lineToHorizontalLine,
                cellRenderers[cellRenderers.length - 1].getOccupiedArea().getBBox().getTop());


        for (int i = 0; i < rows.size(); i++) {
            skewHorizontalLine = (int)(Math.random() * maxSkewHor) + minSkewHor;
            lineToHorizontalLine = (int)(Math.random() * maxLineTo) + minLineTo;
            cellRenderers = rows.get(i);
            // horizontal lines
            canvas.moveTo(cellRenderers[0].getOccupiedArea().getBBox().getX()-lineToHorizontalLine,
                    cellRenderers[0].getOccupiedArea().getBBox().getY()+skewHorizontalLine);
            canvas.lineTo(cellRenderers[cellRenderers.length - 1].getOccupiedArea().getBBox().getRight()+lineToHorizontalLine,
                    cellRenderers[cellRenderers.length - 1].getOccupiedArea().getBBox().getBottom());

            // first vertical line
            Rectangle cellRect = cellRenderers[0].getOccupiedArea().getBBox();
            canvas.moveTo(cellRect.getLeft(), cellRect.getBottom());

            canvas.lineTo(cellRect.getLeft(), cellRect.getTop()+lineToVerticalLine );

            // vertical lines
            for (int j = 0; j < cellRenderers.length; j++) {
                lineToVerticalLine = (int)(Math.random() * maxVerticalLine) + minVerticalLine;


                cellRect = cellRenderers[j].getOccupiedArea().getBBox();
                canvas.moveTo(cellRect.getRight(), cellRect.getBottom()-lineToVerticalLine);
                canvas.lineTo(cellRect.getRight(), cellRect.getTop()+lineToVerticalLine); //ячейки

            }
        }
        canvas.stroke();
    }
}

我想自己绘制自定义边框:)

Answer 1

首先，我们需要正确重写渲染器，即重写getNextRenderer()方法。目前，TableRenderer 的重写存在很大问题，因为 TableRenderer 的无参数构造函数不可访问，并且其他构造函数会执行一些更改状态的隐式工作。但我们仍然可以通过以下代码解决这个问题:

@Override
public IRenderer getNextRenderer() {
    CustomTableRenderer nextTable = new CustomTableRenderer((Table) modelElement);
    nextTable.rows.clear();
    nextTable.rowRange = null;
    return nextTable;
}

免责声明:由于答案使用了 TableRenderer 的私有(private)实现细节，因此将来可能无法工作。它适用于 7.1.6，这是撰写本文时最新发布的版本。您应该为此目的创建一个自定义代码分支。 Pull requests也欢迎。

如果我们查看 TableRenderer 的实现，我们会发现该类包含 heights ( line in code ) 和 countedColumnWidth ( line in code ) )听起来很有趣的字段，但它们是私有(private)。这意味着我们应该创建 iText 的自定义分支(源代码位于 https://github.com/itext/itext7 )，使这些字段 protected 并在我们的子类中使用它们。

您可以在代码中使用反射，风险自负，但不应该使用它，因为它可能不适用于您的 JVM(强烈建议不要更改可访问性修饰符)或者可能不适用于iText 的下一个版本，或者可能由于其他原因而无法工作。我不会在我的答案中添加反射代码以进一步阻止其使用。

我们需要做的就是重写drawBorders()方法。下面的代码已经为线条添加了一些随机性。

private static class CustomTableRenderer extends TableRenderer {
    public CustomTableRenderer(Table modelElement) {
        super(modelElement);
    }

    @Override
    public IRenderer getNextRenderer() {
        CustomTableRenderer nextTable = new CustomTableRenderer((Table) modelElement);
        nextTable.rows.clear();
        nextTable.rowRange = null;
        return nextTable;
    }

    @Override
    protected void drawBorders(DrawContext drawContext) {
        PdfCanvas canvas = drawContext.getCanvas();
        canvas.saveState();
        canvas.setStrokeColor(ColorConstants.RED);

        Random r = new Random();

        // Draw vertical lines
        float curX = getOccupiedAreaBBox().getLeft();
        for (int i = 0; i <= countedColumnWidth.length; i++) {
            canvas.moveTo(curX, getOccupiedAreaBBox().getTop() + 3);
            canvas.lineTo(curX + r.nextInt(4), getOccupiedAreaBBox().getBottom() - 3);
            if (i < countedColumnWidth.length) {
                float curWidth = countedColumnWidth[i];
                curX += curWidth;
            }
        }

        // Draw horizontal lines
        float curY = getOccupiedAreaBBox().getBottom();
        for (int i = 0; i <= heights.size(); i++) {
            canvas.moveTo(getOccupiedAreaBBox().getLeft() - 3, curY);
            canvas.lineTo(getOccupiedAreaBBox().getRight() + 3, curY + r.nextInt(4));
            if (i < heights.size()) {
                float curHeight = heights.get(i);
                curY += curHeight;
            }
        }

        canvas.stroke();
        canvas.restoreState();
    }
}

要激活自定义渲染器，请在添加到文档之前将其设置到表格:

PdfDocument pdfDoc = new PdfDocument(new PdfWriter(outFileName));
Document doc = new Document(pdfDoc);

Table table = new Table(UnitValue.createPercentArray(new float[]{30, 30}));
for (int i = 0; i < 40; i++) {
    table.addCell(new Cell().add(new Paragraph("Hello")));
    table.addCell(new Cell().add(new Paragraph("World")));
    table.startNewRow();
}
table.setNextRenderer(new CustomTableRenderer(table));
doc.add(table);

结果表如下所示: