ElementPlus菜单如何默认打开第一个，router-view里替换变的，menu菜单没有跳转怎么办，开启路由:router=“true“，如何设置点击空格就调用方法

<template>
  <div class="common-layout">
    <el-container>
      <el-header>
        <el-menu
    :default-active="activeIndex"
    class="el-menu-demo"
    mode="horizontal"
    background-color="#545c64"
    text-color="#fff"
    active-text-color="#ffd04b"
    >
    <el-menu-item index="1">Processing Center</el-menu-item>
    <el-sub-menu index="2">
      <template #title>Workspace</template>
      <el-menu-item index="2-1">item one</el-menu-item>
      <el-menu-item index="2-2">item two</el-menu-item>
      <el-menu-item index="2-3">item three</el-menu-item>
      <el-sub-menu index="2-4">
        <template #title>item four</template>
        <el-menu-item index="2-4-1">item one</el-menu-item>
        <el-menu-item index="2-4-2">item two</el-menu-item>
        <el-menu-item index="2-4-3">item three</el-menu-item>
      </el-sub-menu>
    </el-sub-menu>
    <el-menu-item index="3" disabled>Info</el-menu-item>
    <el-menu-item index="4">Orders</el-menu-item>
  </el-menu>
      </el-header>
      <el-main>Main</el-main>
    </el-container>
  </div>
</template>
<script>
export default {
    data(){
        return{
            activeIndex: '1'
        }
    }
};
</script>
 
<style scoped lang="less">
.el-header {
  background-color: #b3c0d1;
  color: #333;
  text-align: center;
  line-height: 60px;
}
.el-main {
  background-color: #e9eef3;
  color: #333;
  text-align: center;
  line-height: 160px;
}
</style>

<el-input @keydown.enter="mySearch()" placeholder="请输入您想看的视频">