给el-table的表头某列添加自定义el-dropdown，点击无效的问题

slot的方式：

                      <el-table-column prop="policyNo" label="号码" :align="columnAlign">
                        <template slot="header">
                          <el-dropdown trigger="hover" @command="handleCommand">
                            <span style="font-size:12px;font-weight:100">
                              号码<i class="el-icon-arrow-down el-icon--right" />
                            </span>
                            <el-dropdown-menu slot="dropdown">
                              <el-dropdown-item command="a">选中全部</el-dropdown-item>
                              <el-dropdown-item command="b">取消选中全部</el-dropdown-item>
                            </el-dropdown-menu>
                          </el-dropdown>
                        </template>
                      </el-table-column>

render-header的方式：

<el-table-column prop="policyNo" :align="columnAlign" :render-header="renderEmotionValue" />

renderEmotionValue(creatElement, { column, $index }) {
      return (
        <el-dropdown onCommand={this.handleCommand }>
          <span style="font-size:12px;font-weight:100">
          号码<i class='el-icon-arrow-down el-icon--right'></i>
          </span>
          <el-dropdown-menu slot='dropdown'>
            <el-dropdown-item command='a' >选中全部</el-dropdown-item>
            <el-dropdown-item command='b'>取消选中全部</el-dropdown-item>
          </el-dropdown-menu>
        </el-dropdown>
      )
    }

注意：

两种方式的触发事件的写法不一样：
@command=“handleCommand” 和 onCommand={this.handleCommand }