<view class='select_box'>  <view class='select' catchtap='selectTap'>    <text class='select_text'>{{selectData[index]}}</text>    <image class='select_img {{show&&"select_img_rotate"}}' src='/image/gobottom.png'></image>       </view>  <view class='option_box' style='height:{{show?(selectData.length>5?300:selectData.length*60):0}}rpx;'>    <text class='option' style='{{index==selectData.length-1&&"border:0;"}}' wx:for='{{selectData}}' wx:key='this' data-index='{{index}}' catchtap='optionTap'>{{item}}</text>  </view></view><!-- show&&"select_img_rotate"-----給顯示框右邊的下拉箭頭添加動畫 height:{{show?(selectData.length>5?300:selectData.length*60):0}}rpx;-----給改變下拉框高度，實現下拉框的顯示隱藏，每個下拉選項的高度為60，下拉框的最大高度這里設置的是300，所以這里寫成當數據長度大于5時，下拉框高度為300，反之下拉框高度為數據長度乘以60 index==selectData.length-1&&"border:0;"-----取消下拉選項的最后一個的下邊框 -->

page{ background: #f3f7f7;}.select_box{ background: #fff; width: 80%; margin: 30rpx auto; position: relative;}.select{ box-sizing: border-box; width: 100%; height: 70rpx; border:1px solid #efefef; border-radius: 8rpx; display: flex; align-items: center; padding: 0 20rpx;}.select_text{ font-size: 30rpx; flex: 1;}.select_img{ width: 40rpx; height: 40rpx; display: block; transition:transform 0.3s;}.select_img_rotate{ transform:rotate(180deg); }.option_box{ position: absolute; top: 70rpx; width: 100%; border:1px solid #efefef; box-sizing: border-box; height: 0; overflow-y: auto; border-top: 0; background: #fff; transition: height 0.3s;}.option{ display: block; line-height: 40rpx; font-size: 30rpx; border-bottom: 1px solid #efefef; padding: 10rpx;}

Page({ data: {  show:false,//控制下拉列表的顯示隱藏，false隱藏、true顯示  selectData:['1','2','3','4','5','6'],//下拉列表的數據  index:0//選擇的下拉列表下標 }, // 點擊下拉顯示框 selectTap(){  this.setData({   show: !this.data.show  }); }, // 點擊下拉列表 optionTap(e){  let Index=e.currentTarget.dataset.index;//獲取點擊的下拉列表的下標  this.setData({   index:Index,   show:!this.data.show  }); }, onLoad: function (options) {  }})