修改表格的导出添加自适应宽度，表头不遮挡

src/main/java/com/ydtech/utils/CustomCellWriteHandler.java

@@ -0,0 +1,111 @@
+package com.ydtech.utils;
+
+import com.alibaba.excel.enums.CellDataTypeEnum;
+import com.alibaba.excel.metadata.Head;
+import com.alibaba.excel.metadata.data.CellData;
+import com.alibaba.excel.metadata.data.WriteCellData;
+import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
+import com.alibaba.excel.write.style.column.AbstractColumnWidthStyleStrategy;
+import com.baomidou.mybatisplus.core.toolkit.CollectionUtils;
+import org.apache.poi.ss.usermodel.Cell;
+
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.StandardCharsets;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ *  @version
+ *  @author: hxl
+ *  @Date: 2024/7/4 10:44
+ *  @Description:  excel 自适应列宽
+ */
+public class CustomCellWriteHandler extends AbstractColumnWidthStyleStrategy {
+    private static final int MAX_COLUMN_WIDTH = 255;
+    private static final int COLUMN_WIDTH_BASE = 255;
+    private final Map<Integer, Map<Integer, Double>> cache = new HashMap<>(8);
+    private Integer relativeRowIndex = -1;
+
+    public CustomCellWriteHandler() {
+    }
+
+    public CustomCellWriteHandler(Integer relativeRowIndex) {
+        //这里是指定从第几行开始自适应。0是第一行，1是第二行，以此类推
+         this.relativeRowIndex = relativeRowIndex;
+    }
+    @Override
+    protected void setColumnWidth(WriteSheetHolder writeSheetHolder, List<WriteCellData<?>> cellDataList, Cell cell, Head head, Integer relativeRowIndex, Boolean isHead) {
+        boolean needSetWidth = isHead || !CollectionUtils.isEmpty(cellDataList);
+        if (needSetWidth) {
+            if (this.relativeRowIndex == -1 || relativeRowIndex >= this.relativeRowIndex) {
+                Map<Integer, Double> maxColumnWidthMap = cache.computeIfAbsent(writeSheetHolder.getSheetNo(), k -> new HashMap<>(16));
+                double columnWidth = this.dataLength(cellDataList, cell, isHead);
+                if (columnWidth >= 0) {
+                    if (columnWidth > MAX_COLUMN_WIDTH) {
+                        columnWidth = MAX_COLUMN_WIDTH;
+                    }
+                    Double maxColumnWidth = maxColumnWidthMap.get(cell.getColumnIndex());
+                    if (maxColumnWidth == null || columnWidth > maxColumnWidth) {
+                        maxColumnWidthMap.put(cell.getColumnIndex(), columnWidth);
+                        writeSheetHolder.getSheet().setColumnWidth(cell.getColumnIndex(), (int) (maxColumnWidthMap.get(cell.getColumnIndex()) * COLUMN_WIDTH_BASE));
+                    }
+                }
+            }
+        }
+    }
+    private double dataLength(List<WriteCellData<?>> cellDataList, Cell cell, Boolean isHead) {
+          if (isHead) {
+              return cell.getStringCellValue().getBytes().length;
+          } else {
+              CellData<?> cellData = cellDataList.get(0);
+              CellDataTypeEnum type = cellData.getType();
+              //禁止这行
+              cell.getCellStyle().setWrapText(false);
+              if (type == null) {
+                  return -1;
+              } else {
+                  switch (type) {
+                      case STRING:
+                          return getExcelWidth(cellData.getStringValue());
+                      case BOOLEAN:
+                      return getExcelWidth(cellData.getBooleanValue().toString());
+                      case NUMBER:
+                          return getExcelWidth(cellData.getNumberValue().toString());
+                       default:
+                           return -1;
+                  }
+              }
+          }
+    }
+      /**     * 调整单元格字符字节宽度，easyExcel默认直接用的UTF-8的byte长度，导致一旦三字节的字符过多就会变得很宽，一字节的字符过多就会不够宽     */
+      private double getExcelWidth(String str){
+          double length = 0.0;
+          char[] chars = str.toCharArray();
+          for(char c : chars){
+              byte[] bytes = this.getUtf8Bytes(c);
+              if(bytes.length == 1){
+                  length += 1.05;
+              }
+              if(bytes.length == 2){
+                  length += 1.5;
+              }
+              if(bytes.length == 3){
+                  length += 1.85;
+              }
+              if(bytes.length == 4){
+                  length += 2.2;
+              }
+          }
+          return length;
+      }
+      private byte[] getUtf8Bytes(char c) {
+          char[] chars = {c};
+          CharBuffer charBuffer = CharBuffer.allocate(chars.length);
+          charBuffer.put(chars);
+          charBuffer.flip();
+          ByteBuffer byteBuffer = StandardCharsets.UTF_8.encode(charBuffer);
+          return byteBuffer.array();
+      }
+    }