excel poi:将前景色应用于空白单元格 [英] excel poi: apply foreground color to blank cells

问题描述

我想使用 poi 将我的 excel 文件的所有单元格设置为某种颜色.但是，我不断收到空白单元格的空指针异常.这是我目前所拥有的:

I want to use poi to set all cells of my excel file to a certain color. however, i keep on getting a nullpointer exception for blank cells. This is what i have so far:

        HSSFWorkbook workBook = new HSSFWorkbook();
        HSSFCellStyle whiteFG = workBook.createCellStyle();
        whiteFG.setFillForegroundColor(HSSFColor.AQUA.index);
        whiteFG.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);

        //each row has 20 columns
        int numColumns = 20;

        for (int colNum = 0 ; colNum < numColumns ; colNum++){  

            HSSFCell cell = row.getCell((short)colNum); 

            if (cell != null){
                cell.setCellStyle(whiteFG);
            }

            else if ( "".equals(cell.getStringCellValue()) ){       
                cell.setCellStyle(whiteFG);
            } 

                            else () {
                                 cell.setCellStyle(whiteFG);
                            }

关于如何为空白单元格着色的任何建议?

any advice on how i can color the blank cells?

推荐答案

你的代码甚至无法编译.

Your code can not even compile.

但是你得到 NullPointerException 的原因是因为这段代码

But the reason you getting a NullPointerException, is because this code

if (cell != null){
   cell.setCellStyle(whiteFG);
}
else if ( "".equals(cell.getStringCellValue()) ){       
    cell.setCellStyle(whiteFG);
}

所有非空单元格都会进入第一个条件，所以唯一进入第二个条件的单元格是null.

All non-null cell will enter the first condition, so the only cell that enter the second condition is null.

*UPDATE : 回复评论 *

我假设您想创建一个带有彩色单元格的新 xls 文件.但是，您的代码遗漏了一点 - 新创建的 Workbook 不包含任何工作表/行/单元格，您必须自己创建一个.

I assume you want to create a new xls file with colored cell. However, your code miss a point - A new created Workbook dose not contains any sheet/row/cell, you have to create one by yourself.

这是我写的一个例子.

HSSFWorkbook workBook = new HSSFWorkbook();
HSSFCellStyle style = workBook.createCellStyle();
style.setFillForegroundColor(HSSFColor.BROWN.index);
style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);

HSSFSheet sheet = workBook.createSheet();
int numRow = 20;
int numCol = 20;

for (int rowIndex = 0; rowIndex < numRow; rowIndex++) {
    HSSFRow row = sheet.createRow(rowIndex);
    for (int colIndex = 0; colIndex < numCol; colIndex++) {
        HSSFCell cell = row.createCell(colIndex);
        cell.setCellStyle(brownBG);
    }
}

FileOutputStream fos = new FileOutputStream("test.xls");
workBook.write(fos);
fos.flush();
fos.close();
System.out.println("done");

您编写的代码使用 getCell(index) 从一行中检索单元格，此方法只会在您编辑新的 xls 文件时返回 null.

The code you wrote use getCell(index) to retrieve cells from a row, this method will only return a null when a you're editing a new xls file.

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