微信小程序顶部栏图片随页面滚动渐变展示隐藏

小程序顶部通栏，展示图片，随着页面滚动，开始渐变展标题记及纯色吸顶样式
主要使用了小程序中的scroll-view组件，通过滚动时触发 bindscroll和滚动到顶部 bindscrolltoupper改变顶部栏的样式效果

 效果如图：

 运用技术：
主要使用了小程序中的scroll-view组件，通过滚动时触发 bindscroll和滚动到顶部 bindscrolltoupper改变顶部栏的样式效果，如果不使用bindscrolltoupper，有时候会在快速滑动到顶部时，不能到最顶部。

代码如下：

index.wxml

<view class="page">
<!--头部导航-->
<view class="page-hd">
  <view class="hd-background"
        style="opacity: {
   
   {opacity == 0 ? 1 : opacity}};background: {
   
   {opacity == 0 ? '#fff' : ''}}">
  </view>
  <view class="hd-text"
        style="opacity: {
   
   {1-opacity}};top: {
   
   {statusNavHeight}}px;height: {
   
   {nMenuButtonHeight}}px;line-height: {
   
   {nMenuButtonHeight}}px;">
    高会答案早知晓
  </view>
</view>
<!--界面主体-->
<view class="page-bd">
  <scroll-view scroll-y style="height: 90vh;" bindscroll="fnScrollEvent" bindscrolltoupper="fnScrollToupper">
    <view class="me-container">
      <view class="me-hd">
        <view class="box-cont">
          <view class="box-white-cont">
            <view class="box-title">讲解介绍</view>
          </view>
        </view>
      </view>
      <view class="me-bd">
      </view>
    </view>
  </scroll-view>
</view>
</view>

index.js

Page({
  data: {
    statusNavHeight: 20,
    nMenuButtonHeight: 40,
    opacity: 1,
  },
  onLoad() {
    // 获取状态栏和胶囊位置
    const {top, height} = wx.getMenuButtonBoundingClientRect()
    this.setData({
      statusNavHeight: top,
      nMenuButtonHeight: height
    })
  },
  // 滚动时触发
  fnScrollEvent(e) {
    let scrolltop = e.detail.scrollTop;
    if (scrolltop > 150) {
      this.setData({
        opacity: 0
      })
      return;
    }
    this.setData({
      opacity: (150 - scrolltop) / 150
    })
  },
  // 滚动到顶部
  fnScrollToupper() {
    this.setData({
      opacity: 1
    })
  },
})

index.wxss

.page{
  height: 100vh;
  width: 100vw;
  display: flex;
  flex-direction: column;
  background: #ffffff;
}
  /* 界面头部 */
.page-hd{
  height: 10vh;
  width: 100%;
}
.hd-background{
  width: 100%;
  height: 100%;
  background: url(https://636c-cloud1-5gfii8jlc56b5045-1306536140.tcb.qcloud.la/wxfile/background.png?sign=6a62c2c13c024f0091a1f8034f4d6155&t=1627552695) ;
  background-repeat: no-repeat;
  background-size: 100vw;
}
.hd-text{
  position: fixed;
  width: 100%;
  text-align: center;
  top: 20px;
  font-size: 28rpx;
  color: #333;
}
.page-bd{
  flex:1;
}
.me-container{
  height: 100%;
  width: 100%;
}
.me-hd{
  width: 100vw;
  height: 40vh;
  background-image: url(https://636c-cloud1-5gfii8jlc56b5045-1306536140.tcb.qcloud.la/wxfile/background.png?sign=6a62c2c13c024f0091a1f8034f4d6155&t=1627552695);
  background-repeat: no-repeat;
  background-size: contain;
  background-position: 0 -10vh;
}
.me-bd{
  height: 100vh;
}
.main-image{
  width: 100%;
  height: 100%;
}
.box-cont{
  padding-top: 200rpx;
  height: 100%;
  box-sizing: border-box;
}
.box-white-cont{
  height: 100%;
  background-color: #fff;
  border-radius: 40rpx 40rpx 0 0;
  display: flex;
  flex-direction: column;
  align-items: center;
}
.box-title{
  margin-top: 20rpx;
  font-size: 28rpx;
}

index.json

{
  "usingComponents": {},
  "navigationStyle": "custom",
  "navigationBarTextStyle": "black"
}