原理
- 将数据源放到一个新建的隐藏的sheet中
- 将选项的子选项的对应字典设置到名称管理器中（名称是当前选项的内容，值是他对应的子菜单的单元格范围，在1里面的sheet中）
- 子菜单的数据根据INDIRECT函数去左边那个单元格获取内容，根据内容去名称管理器中获取字典的key，也就是子菜单的单元格范围
- 使用方式只需要构建CascadeCellBO对象即可，定义级联初始位置和行数，还有选项列表nameCascadeList，他的结构很简单就是name和子nameCascadeList。代码会自动扫描出最深的子菜单层数，根据这个层数构建下拉的个数
优缺点
优点
选项的个数和内容的个数不限制
缺点
- 因为excel的名称管理器的名称有很多限制比如不支持特殊字符、不支持括号、不能数字开头等等，所以选项的内容也会有这些限制
- 因为excel的名称管理器的名称不能相同，所有如果有两个相同二级菜单在不同的一级菜单中，那这两个二级菜单的三级菜单会是一样的
总之使用名称管理器+INDIRECT函数实现的级联下拉列表，只能做一些简单的数据，如果想克服那些缺点，需要用另一种方式，请看下篇文章
代码
import lombok.Data;
import java.util.List;
/**
* @date 2024-01-19 21:05
*/
@Data
public class CascadeCellBO {
/**
* 初始的行
*/
private int rowIndex;
/**
* 初始的列
*/
private int colIndex;
/**
* 行数
*/
private int rowNum;
/**
* 选项
*/
private List<NameCascadeBO> nameCascadeList;
}import lombok.Data;
import java.util.List;
/**
* @date 2024-01-20 10:26
*/
@Data
public class NameCascadeBO {
/**
* 名称
*/
private String name;
/**
* 子选项
*/
private List<NameCascadeBO> nameCascadeList;
}
import com.alibaba.excel.write.handler.SheetWriteHandler;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteWorkbookHolder;
import lombok.Data;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.CellRangeAddressList;
import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.IntStream;
@Data
public class CascadeWriteHandler implements SheetWriteHandler {
private final String dataSourceName;
private final CascadeCellBO cascadeCellBO;
public CascadeWriteHandler(CascadeCellBO cascadeCellBO) {
this.cascadeCellBO = cascadeCellBO;
this.dataSourceName = "dataSource" + System.currentTimeMillis();
}
@Override
public void beforeSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
}
@Override
public void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
//获取工作簿
Sheet sheet = writeSheetHolder.getSheet();
Workbook book = writeWorkbookHolder.getWorkbook();
//创建一个专门用来存放地区信息的隐藏sheet页
//因此不能在现实页之前创建，否则无法隐藏。
Sheet hideSheet = book.createSheet(dataSourceName);
book.setSheetHidden(book.getSheetIndex(hideSheet), true);
// 将具体的数据写入到每一行中，每行的第一个单元格为父级区域的值，后面是子区域。
List<NameCascadeBO> nameCascadeList = cascadeCellBO.getNameCascadeList();
if (nameCascadeList == null || nameCascadeList.isEmpty()) {
return;
}
Row row = hideSheet.createRow(0);
IntStream.range(0, nameCascadeList.size()).forEach(i ->
row.createCell(i).setCellValue(nameCascadeList.get(i).getName()));
// 大类规则
int colIndex = cascadeCellBO.getColIndex();
int firstRowIndex = cascadeCellBO.getRowIndex();
int lastRowIndex = firstRowIndex + cascadeCellBO.getRowNum();
///开始设置（大类小类）下拉框
DataValidationHelper dvHelper = sheet.getDataValidationHelper();
CellRangeAddressList expRangeAddressList = new CellRangeAddressList(firstRowIndex, lastRowIndex, colIndex, colIndex);
String bigEndCol = colIndex2Str(nameCascadeList.size());
DataValidationConstraint bigFormula = dvHelper.createFormulaListConstraint("=" + dataSourceName + "!$A$1:$" + bigEndCol + "$1");
setValidation(sheet, dvHelper, bigFormula, expRangeAddressList, "提示", "你输入的值未在备选列表中，请下拉选择合适的值");
// 小类规则(各单元格按个设置)
// "INDIRECT($A$" + 2 + ")" 表示规则数据会从名称管理器中获取key与单元格 A2 值相同的数据，如果A2是浙江省，那么此处就是浙江省下面的市
// 为了让每个单元格的公式能动态适应，使用循环挨个给公式。
// 循环几次，就有几个单元格生效，次数要和上面的大类影响行数一一对应，要不然最后几个没对上的单元格实现不了级联
AtomicInteger rowId = new AtomicInteger(1);
buildName(book, hideSheet, nameCascadeList, rowId);
int maxLevel = getMaxLevel(nameCascadeList, 0);
for (int num = 1; num < maxLevel; num++) {
String start = colIndex2Str(colIndex + num);
String preStart = "$" + start + "$";
for (int i = firstRowIndex; i <= lastRowIndex; i++) {
CellRangeAddressList rangeAddressList = new CellRangeAddressList(i, i, colIndex + num, colIndex + num);
DataValidationConstraint formula = dvHelper.createFormulaListConstraint("INDIRECT(" + preStart + (i + 1) + ")");
setValidation(sheet, dvHelper, formula, rangeAddressList, "提示", "你输入的值未在备选列表中，请下拉选择合适的值");
}
}
}
// 添加名称管理器
private void buildName(Workbook book, Sheet hideSheet, List<NameCascadeBO> nameCascadeList, AtomicInteger rowId) {
Optional.ofNullable(nameCascadeList).ifPresent(l -> l.forEach(nameCascadeBO -> {
List<NameCascadeBO> childList = nameCascadeBO.getNameCascadeList();
if (childList != null && !childList.isEmpty()) {
Row row = hideSheet.createRow(rowId.getAndIncrement());
row.createCell(0).setCellValue(nameCascadeBO.getName());
IntStream.range(0, childList.size()).forEach(c ->
row.createCell(c + 1).setCellValue(childList.get(c).getName()));
// 添加名称管理器
String endCol = colIndex2Str(1 + childList.size());
String range = "$B$" + rowId.get() + ":$" + endCol + "$" + rowId.get();
Name name = book.createName();
name.setNameName(nameCascadeBO.getName());
name.setRefersToFormula(dataSourceName + "!" + range);
buildName(book, hideSheet, childList, rowId);
}
}));
}
private int getMaxLevel(List<NameCascadeBO> nameCascadeList, int preLevel) {
int curLevel = preLevel + 1;
int maxLevel = curLevel;
for (NameCascadeBO nameCascadeBO : nameCascadeList) {
List<NameCascadeBO> childList = nameCascadeBO.getNameCascadeList();
if (childList != null && !childList.isEmpty()) {
int level = getMaxLevel(childList, curLevel);
maxLevel = Math.max(level, maxLevel);
}
}
return maxLevel;
}
/**
* 设置验证规则
*
* @param sheet sheet对象
* @param helper 验证助手
* @param constraint createExplicitListConstraint
* @param addressList 验证位置对象
* @param msgHead 错误提示头
* @param msgContext 错误提示内容
*/
private void setValidation(Sheet sheet, DataValidationHelper helper, DataValidationConstraint constraint, CellRangeAddressList addressList, String msgHead, String msgContext) {
DataValidation dataValidation = helper.createValidation(constraint, addressList);
dataValidation.setErrorStyle(DataValidation.ErrorStyle.STOP);
dataValidation.setShowErrorBox(true);
dataValidation.setSuppressDropDownArrow(true);
dataValidation.createErrorBox(msgHead, msgContext);
sheet.addValidationData(dataValidation);
}
public static String colIndex2Str(int column) {
if (column <= 0) {
return null;
}
String columnStr = "";
column--;
do {
if (columnStr.length() > 0) {
column--;
}
columnStr = ((char) (column % 26 + (int) 'A')) + columnStr;
column = (int) ((column - column % 26) / 26);
} while (column > 0);
return columnStr;
}
}使用
public static void main(String[] args) {
List<List<String>> header = new ArrayList<>();
header.add(Arrays.asList( "sc2"));
header.add(Arrays.asList( "sc3"));
int colIndex = header.size() - 1;
List<NameCascadeBO> nameCascadeList = new ArrayList<>();
NameCascadeBO nameCascadeBO = new NameCascadeBO();
nameCascadeBO.setName("第一层1");
List<NameCascadeBO> nameCascadeList2 = new ArrayList<>();
NameCascadeBO nameCascadeBO2 = new NameCascadeBO();
nameCascadeBO2.setName("第二层11");
List<NameCascadeBO> nameCascadeList3 = new ArrayList<>();
IntStream.range(0, 400).forEach(i -> {
NameCascadeBO nameCascadeBO3 = new NameCascadeBO();
nameCascadeBO3.setName("第三层11" + i);
nameCascadeList3.add(nameCascadeBO3);
});
nameCascadeBO2.setNameCascadeList(nameCascadeList3);
nameCascadeList2.add(nameCascadeBO2);
nameCascadeBO2 = new NameCascadeBO();
nameCascadeBO2.setName("第二层12");
nameCascadeList2.add(nameCascadeBO2);
nameCascadeBO.setNameCascadeList(nameCascadeList2);
nameCascadeList.add(nameCascadeBO);
nameCascadeBO = new NameCascadeBO();
nameCascadeBO.setName("第一层2");
nameCascadeList2 = new ArrayList<>();
nameCascadeBO2 = new NameCascadeBO();
nameCascadeBO2.setName("第二层21");
nameCascadeList2.add(nameCascadeBO2);
nameCascadeBO2 = new NameCascadeBO();
nameCascadeBO2.setName("第二层22");
nameCascadeList2.add(nameCascadeBO2);
nameCascadeBO.setNameCascadeList(nameCascadeList2);
nameCascadeList.add(nameCascadeBO);
IntStream.range(2, 200).forEach(i -> {
NameCascadeBO item = new NameCascadeBO();
item.setName("第一层" + i);
nameCascadeList.add(item);
});
CascadeCellBO cascadeCellBO = new CascadeCellBO();
cascadeCellBO.setRowIndex(2);
cascadeCellBO.setRowNum(10);
cascadeCellBO.setColIndex(colIndex);
cascadeCellBO.setNameCascadeList(nameCascadeList);
CascadeWriteHandler cascadeWriteHandler = new CascadeWriteHandler(cascadeCellBO);
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
EasyExcelFactory.write(outputStream).head(header)
.registerWriteHandler(cascadeWriteHandler)
.sheet("导入信息").doWrite(new ArrayList<>());
FileUtils.save2File("/Users/admin/aa/导入模板.xlsx", outputStream.toByteArray());
}
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