class="container" scroll-y>
  class="info" id="info" scroll-with-animation scroll-y scroll-top="200" scroll-into-view="{{toView}}" style="height:{{height}}px;">
   class="iitem" id="{{item.id}}" wx:for="{{info_list}}" wx:key="1">
   {{item.id}} . {{item.desc}}
  
 
  class="letter {{active == true " bindtouchstart='start' bindtouchmove='move' bindtouchend='end'>
   class="litem" bindtap='down' data-index="999">☆
   class="litem" wx:for="{{letter_list}}" bindtap='down' wx:for-index="index" wx:key="2" data-index="{{index}}" style="height: {{letter_height}}px;">{{item}}
 
 class="tips" hidden="{{hide}}">{{curView}}

//index.js
//获取应用实例
const app = getApp()
Page({
 data: {
  letter_list: [],
  info_list: [],
  hide: true,
  active: false,
  toView: 'A',
  curView: 'A',
  letter_height: 18
 },
 onLoad: function () {
  this.active = false;
  this.timer = null;
  var letter_list = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'];
  var info_list = [];
  for (var i = 0; i < 26; i++) {
   var obj = {};
   obj.id = letter_list;
   obj.desc = '这是一个用于测试的DEMO。1.目标是用于实现微信好友列表的点击首字母跳转到对应好友位置。2.目标是用于实现微信好友列表的点击首字母跳转到对应好友位置';
   info_list.push(obj);
  }
  this.setData({
   height: app.globalData.height,
   info_list: info_list,
   letter_list: letter_list,
   sHeight: 100 * 26 + 25
  });
 },
 start: function (e) {
  this.setData({
   active: true,
   hide: false
  })
 },
 end: function (e) {
  if (this.timer) {
   clearTimeout(this.timer);
   this.timer = null;
  }
  var moveY = e.changedTouches["0"].clientY - 18, that = this;
  var curIndex = parseInt(moveY / 18);
  var view = this.data.letter_list[curIndex];
  this.setData({
   toView: view,
   active: false
  });
  if (!this.timer) {
   this.timer = setTimeout(function () {
    that.setData({
     hide: true
    })
    that.timer = null;
   }, 1000);
  }
 },
 move: function (e) {
  var moveY = e.changedTouches["0"].clientY - 18;
  var curIndex = parseInt(moveY / 18);
  var view = this.data.letter_list[curIndex];
  this.setData({
   curView: view
  })
 },
 down: function (e) {
  if (this.timer) {
   clearTimeout(this.timer);
   this.timer = null;
  }
  var index = e.currentTarget.dataset.index,
   that = this;
  if (index != 999) {
   var view = this.data.letter_list[index];
   this.setData({
    toView: view,
    curView: view
   })
  } else {
   this.setData({
    toView: 'A',
    curView: '☆'
   })
  }
  if (!this.timer) {
   this.timer = setTimeout(function () {
    that.setData({
     hide: true
    });
    that.timer = null;
   }, 1000);
  }
 }
})

/**index.wxss**/
text {
 font-weight: bold
}
.letter {
 font-size: 12px;
 width: 24px;
 height: 100%;
 position: fixed;
 right: 0;
 top: 0;
 z-index: +999;
}
.litem {
 width: 24px;
 height: 18px;
 line-height: 18px;
 text-align: center;
}
.info {
 font-size: 12px;
 text-align: justify;
 overflow: hidden;
}
.active {
 background: rgba(0, 0, 0, 0.2);
}
.iitem {
 padding: 10rpx 10rpx;
 margin-bottom: 10rpx;
 border-radius: 8rpx;
 background: rgba(222,222,222,0.2);
 box-sizing: border-box;
}
.tips {
 width: 40px;
 height: 40px;
 background: rgba(0,0,0,0.4);
 font-size: 20px;
 text-align: center;
 line-height: 40px;
 color: #fff;
 position: fixed;
 left: 50%;
 top: 50%;
 margin: -20px;
 z-index: +999;
 border-radius: 10rpx;