Itext7 CellRenderer并不总是有效

Question

我正在使用Itext7创建一个带有表格的pdf.
该表占用多个页面.
我还要重写单元格渲染器,将formfield添加到某个单元格.
我注意到当表转到新页面时,第一行不会触发CellRender类的draw方法.
我在下面放了一些代码以便更好地理解.

...
//adding the cells to table
for (int i = 0; i < 10; i++) {
    addRow(table,i);
}
...
//addRow implementation
private void addRow(Table table, int row) throws IOException {
    table.startNewRow();

    PdfFont zapfdingbats = PdfFontFactory.createFont(FontConstants.ZAPFDINGBATS);

    Cell checkBoxCell = new Cell().add(new Paragraph("o").setFont(zapfdingbats).setMargins(9, 0, 0, 11)).setKeepTogether(true);
    checkBoxCell.setNextRenderer(new CheckboxCellRenderer(checkBoxCell, "cb"+row));
    table.addCell(checkBoxCell);
    ...
    //other cells here
}
...
//The implementation of the custom CellRender
protected class CheckboxCellRenderer extends CellRenderer {
    protected String name;

    public CheckboxCellRenderer(Cell modelElement, String name) {
        super(modelElement);
        this.name = name;
    }
    //this method is not triggered for the first row when a new page is created
    @Override
    public void draw(DrawContext drawContext) {
        System.out.println(name);
        super.draw(drawContext);
        float x = getOccupiedAreaBBox().getLeft();
        float y = getOccupiedAreaBBox().getBottom();
        float width = getOccupiedAreaBBox().getRight()-getOccupiedAreaBBox().getLeft();
        float height = getOccupiedAreaBBox().getTop()-getOccupiedAreaBBox().getBottom();
        Rectangle rect = new Rectangle(x+5, y+5, width-10, height-10);
        PdfTextFormField pdfTextFormField = PdfFormField.createText(drawContext.getDocument(), rect, name);
        PdfAcroForm.getAcroForm(drawContext.getDocument(), true).addField(pdfTextFormField);
    }
}

我究竟做错了什么？

Answer 1

你没有覆盖一个非常重要的方法:public IRenderer getNextRenderer().

如果单元格无法放置在页面上,iText会创建一个溢出单元格(请参阅protected AbstractRenderer createOverflowRenderer(int layoutResult)方法.如果getNextRenderer默认情况下不覆盖iText,则使用其getModelElement()创建简单的CellRenderer.

所以我建议你添加summat: @Override public IRenderer getNextRenderer() { return new CheckboxCellRenderer(getModelElement(), name); }

我已经使用您的代码创建了下一个示例,它可以按预期工作.`

public class ArrayToTable extends GenericTest {
public static final String DEST = "./target/test/resources/sandbox/tables/array_to_table.pdf";

public static void main(String[] args) throws Exception {
    File file = new File(DEST);
    file.getParentFile().mkdirs();
    new CustomRendererTest().manipulatePdf(DEST);
}

@Override
protected void manipulatePdf(String dest) throws Exception {
    PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
    Document doc = new Document(pdfDoc);

    Table table = new Table(1);
    //adding the cells to table
    for (int i = 0; i < 25; i++) {
        addRow(table, i);
    }

    doc.add(table);
    doc.close();
}

    //addRow implementation
    private void addRow(Table table, int row) throws IOException {
        table.startNewRow();

        PdfFont zapfdingbats = PdfFontFactory.createFont(FontConstants.ZAPFDINGBATS);

        Cell checkBoxCell = new Cell().add(new Paragraph("o").setFont(zapfdingbats).setMargins(9, 0, 0, 11)).setKeepTogether(true);
        checkBoxCell.setNextRenderer(new CheckboxCellRenderer(checkBoxCell, "cb"+row));
        table.addCell(checkBoxCell);
        //other cells here
    }

    //The implementation of the custom CellRender
    protected class CheckboxCellRenderer extends CellRenderer {
        protected String name;

        public CheckboxCellRenderer(Cell modelElement, String name) {
            super(modelElement);
            this.name = name;
        }
        //this method is not triggered for the first row when a new page is created
        @Override
        public void draw(DrawContext drawContext) {
            System.out.println(name);
            super.draw(drawContext);
            float x = getOccupiedAreaBBox().getLeft();
            float y = getOccupiedAreaBBox().getBottom();
            float width = getOccupiedAreaBBox().getRight()-getOccupiedAreaBBox().getLeft();
            float height = getOccupiedAreaBBox().getTop()-getOccupiedAreaBBox().getBottom();
            Rectangle rect = new Rectangle(x+5, y+5, width-10, height-10);
            PdfTextFormField pdfTextFormField = PdfFormField.createText(drawContext.getDocument(), rect, name);
            PdfAcroForm.getAcroForm(drawContext.getDocument(), true).addField(pdfTextFormField);
        }

        @Override
        public IRenderer getNextRenderer() {
            return new CheckboxCellRenderer(getModelElement(), name);
        }

    }

}

Answer 2

如果您转到新页面,那么您将Renderer被丢弃并Renderer创建一个新对象.这样做是为了避免在模型对象发生变化的情况下混淆状态.在这种情况下,该方法getNextRenderer称为:

/**
 * Gets a new instance of this class to be used as a next renderer, after this renderer is used, if
 * {@link #layout(LayoutContext)} is called more than once.
 * @return new renderer instance
 */
IRenderer getNextRenderer();

如果您只是在自定义CheckboxCellRenderer类中重写此方法,那么您应该没问题:

@Override
public IRenderer getNextRenderer() {
    return new CheckboxCellRenderer(getModelElement(), name);
}