java - CELL_TYPE_ERROR 有什么用？

Question

我想了解单元格类型CELL_TYPE_ERROR在apache poi中的使用。我尝试了以下代码，没有看到错误。

Workbook wb = new XSSFWorkbook();
Row row = sheet1.createRow(0);
Cell cell = row.createCell(0);

cell.setCellType(Cell.CELL_TYPE_ERROR);
cell.setCellValue(234);
System.out.println("error cell value-"+ cell.getNumericCellValue()); //this prints 234.0

此外，我想了解如果我们不手动设置单元格的类型，单元格是否可以为 error 类型。

Answer 1

查看代码中的注释。

import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.xssf.usermodel.*;
import org.apache.poi.ss.usermodel.*;

import java.io.FileOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

class CellTypeErrorTest {

 public static void main(String[] args) {
  Workbook wb = new XSSFWorkbook();
  Sheet sheet = wb.createSheet("Sheet1");
  Row row = sheet.createRow(0);
  Cell cell = row.createCell(0);

  //The following works, but it makes no sense, because the cell will have no real content.
  //If you wants to see, how this will be shown into the Workbook, then comment out the
  //following code that overwrites the Cell with numeric content.
  cell.setCellType(Cell.CELL_TYPE_ERROR);
  cell.setCellErrorValue(FormulaError.DIV0.getCode());
  System.out.println("error cell value-"+ FormulaError.forInt(cell.getErrorCellValue()).getString());

  //If you put real content in the cell, then the CELL_TYPE_ERROR goes away, if the content 
  //not produces ERROR.
  cell.setCellValue(234);
  System.out.println(cell.getCellType()); //0 == CELL_TYPE_NUMERIC

  //If you put a Formula in the Cell, it will not be evaluated automatically.
  //So there is no error, even the formula will produce error if it will be evaluated.
  cell = row.createCell(1);
  cell.setCellFormula("1/0");
  System.out.println(cell.getCellType()); //2 == CELL_TYPE_FORMULA

  //It you need to check if a formula produces error, then you have to evaluate it.
  FormulaEvaluator evaluator = wb.getCreationHelper().createFormulaEvaluator();
  CellValue cellValue = evaluator.evaluate(cell);
  System.out.println(cellValue.getCellType()); //5 == CELL_TYPE_ERROR
  if (cellValue.getCellType() == Cell.CELL_TYPE_ERROR) {
   System.out.println("error cell value-"+ FormulaError.forInt(cellValue.getErrorValue()).getString());
  }

  try {
   FileOutputStream fileOut = new FileOutputStream("workbook.xlsx");
   wb.write(fileOut);
   fileOut.close();
  } catch (FileNotFoundException fnfex) {
  } catch (IOException ioex) {
  }

 }
}

结论:

Cell.CELL_TYPE_ERROR 是检测单元格内容是否产生错误所必需的。手动设置它基本上没有意义。

可以使用cell.setCellErrorValue手动将其设置为没有实际内容的单元格。但这大多没有意义，因为如果单元格获取真实内容并且不会产生错误，则 CellType 会自动更改为另一种类型。

POI 不会自动计算单元格公式。带有公式的单元格类型始终为 Cell.CELL_TYPE_FORMULA。因此，要检查单元格公式是否产生错误，我们必须手动计算，然后检查计算的CellValue的CellType。请参阅:http://poi.apache.org/spreadsheet/eval.html

问候

阿克塞尔