uniapp如何实现自定义设置导航栏

"navigationStyle": "custom"

<template>    <view>        <view>            <view>                <view></view>            </view>            测试辣        </view>    </view></template><script>    export default {        data () {            return {                demo: {                    top: 0,                    height: 0                }            }        },        created () {            const demo = uni.getMenuButtonBoundingClientRect()            this.demo.top = demo.top            this.demo.height = demo.height        }    }</script><style>    .demo{        position: relative;        display: flex;        align-items: center;        justify-content: center;        background: #fff;        font-size: 26rpx;        .left{            float: left;            position: absolute;            width: max-content;            height: max-content;            top: 0;            bottom: 0;            left: 20rpx;            margin: auto;            .iconfont{                color: #3C3C3C;            }        }    }</style>