element-plus:el-dropdown组件利用popover制作二级菜单

利用组件el-popver组件，在组件内放入el-menu或者自己用a标签写加上样式。

注意：el-dropdown点击打开=>trigger="click"，el-popver则使用鼠标滑过=>trigger="hover"

代码如下：

<el-dropdown v-if="$store.state.user" trigger="click">
  <div>
    <span>{{$store.state.username}}</span>
    <el-avatar :size="24" :src="require('../assets/img/touxiang.png')"></el-avatar>
  </div>
  <template #dropdown>
    <el-dropdown-menu>
      <el-dropdown-item>
        <el-popover placement="left-start" trigger="hover" :offset="15">
          <template #reference>
            <span>个人中心</span>
          </template>
          <el-menu mode="vertical" :default-active="$route.meta.route" router>
            <el-menu-item index="/usercenter/users">用户</el-menu-item>
            <el-menu-item index="/usercenter/nft">NFTs</el-menu-item>
            <el-menu-item index="/usercenter/contract">合同</el-menu-item>
          </el-menu>
        </el-popover>
      </el-dropdown-item>
      <el-dropdown-item @click="go('/usercenter/reset')">修改密码</el-dropdown-item>
      <el-dropdown-item @click="go('/usercenter/info')">修改资料</el-dropdown-item>
      <el-dropdown-item @click="isLogout">退出登录</el-dropdown-item>
    </el-dropdown-menu>
  </template>
</el-dropdown>