微信小程序 实现listview带字母滑动

 <!--字母滑动-->
 <view class="letter-position" wx:if="{{filtertype == 'name'}}" hidden="{{lettershow?'true':''}}" style="z-index:{{zindex}}" catchtouchstart="handleralphatap" catchtouchmove="handlermove" catchtouchend="handlerend">
  <image class="no-stars star-icon" data-loc="star" src="../img/no-stars.png"></image>
  <text class="letter" wx:for="{{groups}}" wx:for-item="group" data-loc="{{group.id}}" wx:key="l_{{group.id}}">
   {{group.id}}
  </text>
  <text class="letter no-letter">
   #
  </text>
 </view>

<scroll-view scroll-into-view="{{locationto}}" bindscrolltolower="onscrolllower" scroll-y="{{trues}}" style="height: {{clientheihgt?clientheihgt+'px':'auto'}}" bindscroll="scroll" scroll-top="{{scrolltop}}" hidden="{{favoritecards.length==0 && starcards.length ==0}}">

handleralphatap(e) {
  var ap = e.target.dataset.loc; //字母
  this.setdata({
   locationto: ap
  });

  var list = this.data.groups;
  this.offsettop = (this.data.clientheihgt - list.length * 16) / 2;

 },

 handlermove(e) {
  var _this = this;
  var list = this.data.groups;
  var movey = e.touches[0].clienty;
  var ry = movey - this.offsettop;
  if (ry >= 0) {
   var index = math.ceil((ry - 16) / 16);
   if (0 <= index && index < list.length) {
    _this.setdata({
     locationto: list[index].id,
     nonwapid: list[index].id,
     fly: false,
     //nonwap: list[index]
    });
    // _this.setdata({
    //  nonwapid:_this.data.nonwap.id
    // }); 
   }

  }
 },
 handlerend(e) {
  //  try{
  this.setdata({
   nonwapid: '',
   fly: true,
   // locationto:this.data.nonwap.id
  });
  // }catch(e){

  // }
  var _this = this;
  this.setdata({
   scottttp: e.currenttarget.dataset.scrolltop
  });

 },