使用 jxl 库使用 Java 向 Excel 文件中的单元格添加注释

Question

我正在尝试向 Excel 中的单元格添加注释。我正在使用 jxl 库来做到这一点：

   cell = sheet.getWritableCell(1, 2); // cols, rows
   WritableCellFeatures wcf = cell.getWritableCellFeatures();
   wcf.setComment("comment2");

最后一行返回：Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException。尽管进行了多次尝试，但我无法修复它。帮助将不胜感激。谢谢你。

--EDIT--
这是修改后的addNumber方法：

private static void addNumber(WritableSheet sheet, int column, int row,
        double d) throws WriteException, RowsExceededException {

    Number number;
    number = new Number(column, row, d, timesStandard);

    //sheet.addCell(number); // need to add the cell first

    if (user wants to add a comment) {
        WritableCellFeatures wcf = new WritableCellFeatures();
        wcf.setComment("the comment");
        number.setCellFeatures(wcf);
    }

    //sheet.addCell(number); // but may need to add the cell with comments as well
}

Answer 1

您之前是否在该位置添加过单元格？问题是您无法在 an 上设置单元格特征EmptyCell，并且它将始终null作为其单元格特征返回。

如果您先添加一个单元格，它就会起作用（为了清楚起见，省略了 try/catch），如下面的代码所示。请注意，它还会首先WritableCellFeatures在新Label单元格上设置 a ，因为最初单元格特征始终为null。

            WritableWorkbook book = Workbook.createWorkbook(new File("output.xls"));
            WritableSheet sheet = book.createSheet("Some Sheet", 0);

            Label label = new Label(1, 2, "Some label"); 
            sheet.addCell(label); // add cell!

            WritableCellFeatures wcf = new WritableCellFeatures();
            wcf.setComment("Hello!");

            // set cell features!
            label.setCellFeatures(wcf);

            book.write();
            book.close();

将其与OP中的方法一起使用：

我修改了方法以返回创建的（和添加的！）Number实例。如果您不希望这样做，您可以使用WritableWorkbook.getWritableCell()相同的行/列来检索相同的单元格。

public static void main(String[] args) throws IOException, RowsExceededException, WriteException {

    File file = new File("output.xls");
    WritableWorkbook workbook = Workbook.createWorkbook(file);
    WritableSheet sheet = workbook.createSheet("First Sheet", 0);

    Number number = addNumber(sheet, 3, 2, 565d);

    WritableCellFeatures wcf = number.getWritableCellFeatures();
    if (wcf == null) wcf = new WritableCellFeatures();
    wcf.setComment("the comment");
    number.setCellFeatures(wcf);

    workbook.write(); 
    workbook.close();

}

private static Number addNumber(WritableSheet sheet, int column, int row,
        double d) throws WriteException, RowsExceededException {

    Number number = new Number(column, row, d, timesStandard);
    sheet.addCell(number); // need to add the cell first
    return number;
}