本文主要是介绍微信小程序原生的下拉框组件，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

前言

近日开发微信小程序时，需要一个下拉框的组件，使用和PC端下拉框一样的方式会显得很丑，于是发现微信官方API有个wx.showActionSheet，但是有诸多限制，例如：最大长度只能是6项，多选等等。

由于业务需要，下面用到下拉框（actionSheet）支持自定义 高度， 选项，单选，多选，以及遮罩层的透明度等参数。

效果

看完效果直接上代码

组件代码

index.js

Component({
  properties: {
    //数据集
    options: {
      type: JSON,
      value: ''
    },
    //内容层高度
    topsHeight: {
      type: String,
      value: '40%'
    },
    //遮罩层透明度
    opacity: {
      type: String,
      value: '0.5'
    },
    //是否单选
    IsSingle: {
      type: Boolean,
      value: true
    }
  },
  data: {
    isShow: false,
    contentAnimate: null, //内容动画
    overlayAnimate: null, //遮罩层动画
  },
  methods: {

    /**
     * 关闭
     */
    _close: function () {
      var that = this;
      this.contentAnimate.bottom("-40%").step();
      this.overlayAnimate.opacity(0).step();
      this.setData({
        contentAnimate: this.contentAnimate.export(),
        overlayAnimate: this.overlayAnimate.export(),
      });
      setTimeout(function () {
        that.setData({
          isShow: false,
        })
      }, 200)
    },
    /**
     * 显示
     */
    _show: function () {
      var that = this;
      that.setData({
        isShow: true,
      })
      // 容器上弹
      var contentAnimate = wx.createAnimation({
        duration: 200,
      })
      contentAnimate.bottom(0).step();
      //遮罩层
      var overlayAnimate = wx.createAnimation({
        duration: 250,
      })
      overlayAnimate.opacity(`${this.properties.opacity}`).step();
      this.contentAnimate = contentAnimate;
      this.overlayAnimate = overlayAnimate;
      this.setData({
        contentAnimate: contentAnimate.export(),
        overlayAnimate: overlayAnimate.export(),
      })
    },
    /**
     * 设置选中
     */
    _setSelect: function (even) {
      let data = this.data.options;
      let index = even.currentTarget.dataset.index;
      if (this.properties.IsSingle) {
        data.forEach((item, i) => {
          if (i == index) {
            item.Selected = !item.Selected;
          }
          else {
            item.Selected = false;
          }
        });
      }
      else {
        data[index].Selected = !data[index].Selected;
      }
      this.setData({
        options: data
      });
    },
    /**
     * 确定 
     * */
    _submit: function () {
      this.triggerEvent('OnSelectFinish', this.properties.options);
      this._close();
    },
    /**
     * 外部方法调用，显示组件
     */
    showPopup: function () {
      this._show();
    }
  }
})

index.json

{
  "usingComponents": {},
  "component": true
}

index.wxml

<view class="selectComponent" style="height:{{topsHeight}};bottom: -{{topsHeight}};" wx:if="{{isShow}}" animation="{{contentAnimate}}">
<image src="../../images/icon_close_gray.png" class="close" catchtap="_close"></image>
  <view class="select-ul">
    <view class="select-li" wx:for="{{options}}">
      {{item.Text}}
      <block wx:if="{{IsSingle}}">
        <view class="checkbox {{item.Selected ? 'singlechecked' : 'singleunchecked'}}" data-index="{{index}}" bindtap="_setSelect"></view>
      </block>
      <block wx:else>
        <view data-single="{{IsSingle}}" class="checkbox {{item.Selected ? 'checked' : 'unchecked'}}" data-index="{{index}}" bindtap="_setSelect"></view>
      </block>
    </view>
  </view>
  <view class="SubmitBtn" bindtap="_submit">
    确 定
  </view>
</view>
<!-- 遮罩层 -->
<view class="overlay" catchtap ="_close" wx:if="{{isShow}}" animation="{{overlayAnimate}}"></view>

index.wxss

.overlay{
  position: fixed;
  top: 0;
  left: 0;
  z-index: 1;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0);
}

.selectComponent{
  background-color: white;
  position: fixed;
  /* bottom: -40%; */
  left: 0;
  width: calc( 100% - 100rpx);
  /* height: 40%; */
  z-index: 10000;
  padding:20rpx 50rpx;
  border-top-right-radius: 20rpx;
  border-top-left-radius: 20rpx;
}
.SubmitBtn{
  border-top: 10px #F7F8FA solid;
  height: 120rpx;
  text-align: center;
  line-height: 90rpx;
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  background-color: #4876F9;
  color: white;
}
.select-ul{
  height: calc( 100% - 200rpx);
  overflow: auto;
  margin-top: 50rpx;
}
.select-li{
  text-align: left;
  line-height: 80rpx;
  height: 80rpx;
  position: relative;
  font-size: 14px;
}
.checkbox{
  top:24rpx !important;
  right: 30rpx !important;
  height: 34rpx;
}
.close{
  width: 14px;
  height: 14px;
  position: absolute;
  right: 30rpx;
  top: 30rpx;
}
.checkbox{
  width: 30rpx;
  height: 30rpx;
  top: 58rpx;
  right: 0rpx;
  position: absolute;
  background-repeat: no-repeat;
  background-size: 30rpx;
}
.singlechecked{
  background-image: url("data:image/png;base64,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");  
}
.singleunchecked{
  background-image: url("data:image/png;base64,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");  
}
.checked{
  background-image: url("data:image/png;base64,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");  
}
.unchecked{
  background-image: url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABYAAAAWCAYAAAGzs1ytAAAAAXNSR0IArs4c6QAAAERlWElmTU0AKgAAAAgAAYdpAAQAAAABAAAAGgAAAAAAA6ABAAMAAAABAAEAAKACAAQAAAABAAAAFqADAAQAAAABAAAAFgAAAAAcITNaAAAAaUlEQVQ4EWNcuHDhfwYYQOYwwQRBNCOyDLIEGhuXMhTDkPXglCDWRmTDqMjG5RFsVuD0wyBWTJvgBYXaUAyNYe9mBlLSM7Zki02M5NjGZgguMZKiBJch2MRHDYaHymhQ0D4oaFPQAt0NAFtBH+4zl50uAAAAAElFTkSuQmCC");  
}

调用页面代码

index.wxml

<!-- 出库类型下拉框 -->
<select id="select" options="{{options}}"  topsHeight="{{topsHeight}}" opacity="{{opacity}}" IsSingle="{{IsSingle}}" 
bind:OnSelectFinish="SelectFinish"></select>

json文件需要引用组件

{
  "usingComponents": {
    "select":"../../../../components/select/index"
  }
}

js 文件

const app = getApp();
Page({
  /**
   * 页面的初始数据
   */
  data: {
    options: [], //数据集
    topsHeight: "30%", //高度
    opacity: "0.5", //透明度
    IsSingle: true //是否单选
  },
  /**
   * 生命周期函数--监听页面加载
   */
  onl oad: function (options) {
    //初始化出库类型
    this.initExitType();
  },
  /**
   * 初始化出库类型
   */
  initExitType() {
    /* 这里是系统封装的函数，下面需要换成自己的访问代码*/
    var that = this;
    HTTP.GetExitTypeList().then((res) => {
      if (res.ErrorCode === 0) {
        var newArray = [];
        res.Data.forEach(item => {
          newArray.push({ "Text": item.Text, "Value": item.Value });
        });

        that.setData({
          options: res.Data
        });
      }
    })
  },
  /**
   * 下拉框选择完成事件
   */
  SelectFinish: function (even) {
	  console.log(even.detail)
  },
  /**
   * 显示出库类型下拉框
   */
  selectStockOutType: function () {
    this.selectComponent("#select").showPopup();
  }
})

效果图

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