element-ui的第三級(jí)導(dǎo)航菜單被同時(shí)展開(kāi)或收起

element ui的三級(jí)導(dǎo)航菜單，點(diǎn)擊任意一個(gè)第二級(jí)導(dǎo)航時(shí)，所有的三級(jí)導(dǎo)航都會(huì)被展開(kāi)

如圖，當(dāng)我點(diǎn)擊二級(jí)菜單如攝像頭時(shí)，wifi和攝像頭的子菜單都會(huì)同時(shí)展開(kāi)或關(guān)閉
代碼部分：

<template v-for="item in items">

                        <el-submenu :index="item.index">
                            <template slot="title">
                                <img :src="item.icon" alt="">{{ item.title }}
                            </template>
                            <template v-for="(subItem,i) in item.subs" >
                                    <template v-if="subItem.sonSubs">
                                        <el-submenu   :index="subItem.index">
                                            <template slot="title">
                                                <img :src="'../../../static/img/'+subItem.mark+'.svg'" alt="">{{ subItem.title }}
                                            </template>
                                            <el-menu-item v-for="(sonSubItem,r) in subItem.sonSubs"  :index="sonSubItem.index">
                                                <img :src="'../../../static/img/'+sonSubItem.mark+'.svg'" alt="">{{sonSubItem.title}}
                                            </el-menu-item>
                                        </el-submenu>
                                    </template>
                                </template>
                        </el-submenu>
            </template>