一、 实现思路

通过 wx.getSystemInfoSync 计算得到的整个导航栏高度，pages.json 设置自定义导航：

{
    "path": "pages/mine/index",
    "style": {
      "navigationBarTitleText": "我的",
      "navigationStyle":"custom" 
    }
  }

二、 代码解析

<template>
    <view class="nav-box" :style="{'height':height+'px','background':bgColor}">
      <!-- 自定义导航栏 -->
      <view class="status_bar" :style="{'height':statusBarHeight+'px'}">
            <!-- uni-ui这里是状态栏 -->
      </view>
      <!-- 胶囊位置信息 -->
      <view class="nav-main flex align-center justify-center" :style="{height: navBarHeight+'px'}">
        <view class="nav-main-back" @click="back" v-if="backIcon">
          <uni-icons type="back" size="26" color="#fff"></uni-icons>
        </view>
        <text class="nav-main-title">{{title}}</text>
      </view>
    </view>
</template>
 
<script>
  export default {
    props:{
      bgColor: {type:String,default: "#F5F5F5"},
      backIcon: {type: Boolean, default: true},
      title: {type:String,default:"我的"}
    },
    data() {
        return {
          //总高度
          height: 0,
          //胶囊位置信息
          menuButtonRect: {},
          //状态栏的高度
          statusBarHeight: 0 ,
          //导航栏的高度
          navBarHeight: 0
        }
    },
    created() {
          //this.height = wx.getStorageSync('navBarHeight')
          this.getHeight();
    },
    methods: {      
      //获取屏幕导航栏高度
      getHeight(){
        if (wx.canIUse('getMenuButtonBoundingClientRect')) {
          let sysInfo = wx.getSystemInfoSync(); //状态栏的高度
          this.statusBarHeight = sysInfo.statusBarHeight;
          // 胶囊位置信息
          let rect = wx.getMenuButtonBoundingClientRect();
          this.menuButtonRect = JSON.parse(JSON.stringify(rect));
          // 导航栏高度
          let navBarHeight = (rect.top-sysInfo.statusBarHeight)*2+rect.height;
          this.navBarHeight = navBarHeight;
          // 自定义导航栏的高度
          this.height = sysInfo.statusBarHeight + navBarHeight;
        } else {
          wx.showToast({
            title: '您的微信版本过低，界面可能会显示不正常',
            icon: 'none',
            duration: 4000
          });
        }
      },
      //返回
      back() {
            uni.navigateBack({
                 delta: 1
            })
      },
    }
  }
</script>
 
<style lang="scss" scoped>
.status_bar {
        // height: var(--status-bar-height);
        width: 100%;
        // background:#ff0;
    }
    .nav-main{
        position: relative;
        // background:#f00;
    .nav-main-back{
      position: absolute;left: 10rpx;
    }
    .nav-main-title{
    color:#fff;font-size:16px;
    }
}
</style>

三、 页面使用

<template>
    <view class="box">
        <MyNav title="我的" bgColor="" :backIcon="false"></MyNav>
    </view>
</template>
<script>
    import MyNav from "@/components/my-navbar.vue"
    export default {
        components: {
            MyNav
        },
    }
</script>