使用jxl库向使用Java的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。尽管许多尝试，我无法修复它。帮助将不胜感激。谢谢。

- 编辑 -
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

你有以前添加在那个位置的单元格？问题是您无法设置EmptyCell上的单元格功能，并且它始终会返回null作为其单元格功能。

如果您先添加一个单元格，它会起作用（为了清晰起见，省略了try/catch），如下面的代码所示。请注意，它也首先在新的Label单元格上设置WritableCellFeatures，因为最初单元格功能始终为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(); 

在OP的方法，使用这样的：

我修改返回创建Number实例的方法（和增加！）。如果你不想这样做，你可以使用相同的行/列使用WritableWorkbook.getWritableCell()取代同一个单元格。

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; 
} 

Answer 2

从意见和：

• http://www.docjar.org/html/api/jxl/demo/ReadWrite.java.html
• http://kickjava.com/src/jxl/demo/Write.java.htm

我做了这个：

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); 

    if (user wants to add a comment) { 
    WritableCell cell = sheet.getWritableCell(column, row) 
    Label l = (Label) cell; 
    WritableCellFeatures cellFeatures = new WritableCellFeatures(); 
    cellFeatures.setComment("the cell comment"); 
    l.setCellFeatures(cellFeatures); 
    sheet.addCell(l); 
    } 

}