我有一个 PdfPTable 命名表，在它的单元格中，我成功地创建了简单的文本、复选框和文本字段。现在我正在尝试创建一个包含组合框（下拉列表）的列，我使用了与添加前面的组件几乎相同的逻辑，但是，组合框不会显示在pdf中的表格单元格中。

private void insertComboBox(PdfPTable table) throws DocumentException, IOException {
        PdfFormField selectGroup = PdfFormField.createEmpty(writer);
        selectGroup.setFieldName("myCombos");
        String[] options = {"Choose first option", "Choose second option", "Choose third option"};
        String[] exports = {"option1", "option2", "option3"};
        PdfPCell cell = new PdfPCell();
        cell.setCellEvent(new SelectCellEvent(selectGroup, "combo1", exports, options));
        cell.setMinimumHeight(20);
        table.addCell(cell);
        writer.addAnnotation(selectGroup);
    }
``` `writer` 在上一个 `insertComboBox` 方法的执行方式如下：

ByteArrayOutputStream baos = createTemporaryOutputStream();
Document document = new Document(PageSize.A4, 30, 30, 30, 30);
this.writer = PdfWriter.getInstance(document, baos);

selectcellevent.java

public class SelectCellEvent implements PdfPCellEvent {
protected PdfFormField selectGroup;
protected String name;
protected String[] exports;
protected String[] options;
protected BaseFont font;

    public SelectCellEvent(PdfFormField selectGroup, String name, String[] exports, String[] options)
            throws DocumentException, IOException {
        this.selectGroup = selectGroup;
        this.name = name;
        this.exports = exports;
        this.options = options;
        font = BaseFont.createFont(BaseFont.TIMES_ROMAN, BaseFont.CP1250, BaseFont.NOT_EMBEDDED);
        font.setSubset(false);
    }
    public void cellLayout(PdfPCell cell, Rectangle position, PdfContentByte[] canvases) {
        PdfWriter writer = canvases[0].getPdfWriter();
        TextField tf = new TextField(writer, position, name);
        tf.setFont(font);
        tf.setBorderStyle(PdfBorderDictionary.STYLE_BEVELED);
        tf.setVisibility(TextField.VISIBLE_BUT_DOES_NOT_PRINT);
        tf.setBorderColor(BaseColor.GRAY);
        tf.setChoiceExports(exports);
        tf.setChoices(options);
        tf.setAlignment(Element.ALIGN_CENTER);
        try {
            selectGroup.addKid(tf.getComboField());
        } catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

}

请注意，当我运行我基本上复制的代码时，会在一个空白的pdf文档中创建一个组合框。所以我的适应一定有问题。与我的适应。