保持一个子菜单展开

static/html/setting_left.html

@@ -7,7 +7,8 @@
         background-color="#222d32"
         text-color="#b8c7ce"
         active-text-color="#fff"
-        default-active="{{.tab_index}}" :default-openeds="openIndex">
+        default-active="{{.tab_index}}" :default-openeds="openIndex"
+        unique-opened="true">
     <el-submenu index="1">
         <template slot="title">
             <i class="el-icon-s-custom"></i>