参考链接：
（1）小程序—搜索框实现
https://blog.csdn.net/Ariel_201311/article/details/81295862

效果图

wxml文件

 <!--搜索框  -->
<view class="weui-search-bar">
  <view class="weui-search-bar__form">
    <!--点击之后，出现input框  -->
    <view class="weui-search-bar__box">
      <icon class="weui-icon-search_in-box" type="search" size="14"></icon>
      <input type="text" class="weui-search-bar__input" placeholder="搜索" value="{{inputVal}}" focus="{{inputShowed}}" bindinput="inputTyping" />
      <!--输入款字数大于0，则显示清除按钮  -->
      <view class="weui-icon-clear" wx:if="{{inputVal.length > 0}}" bindtap="clearInput">
        <icon type="clear" size="14"></icon>
      </view>
    </view>
    <!--没点击之前，只是一些文字和图标  -->
    <label class="weui-search-bar__label" hidden="{{inputShowed}}" bindtap="showInput">
      <icon class="weui-icon-search" type="search" size="14"></icon>
      <view class="weui-search-bar__text">搜索</view>
    </label>
  </view>
  <!--动态出现的“取消”键  -->
  <view class="weui-search-bar__cancel-btn" hidden="{{!inputShowed}}" bindtap="hideInput">取消</view>
</view>

wxss文件

.weui-search-bar {
  position: relative;
  padding: 8px 10px;
  display: -webkit-box;
  display: -webkit-flex;
  display: flex;
  box-sizing: border-box;
  background-color: #EFEFF4;
  border-top: 1rpx solid #D7D6DC;
  border-bottom: 1rpx solid #D7D6DC;
  
}
.weui-icon-search {
  margin-right: 8px;
  font-size: inherit;
}
.weui-icon-search_in-box {
  position: absolute;
  left: 10px;
  top: 7px;
}
.weui-search-bar__text {
  display: inline-block;
  font-size: 14px;
  vertical-align: middle;
}
.weui-search-bar__form {
  position: relative;
  -webkit-box-flex: 1;
  -webkit-flex: auto;
          flex: auto;
  border-radius: 5px;
  background: #FFFFFF;
  border: 1rpx solid #E6E6EA;
}
.weui-search-bar__box {
  position: relative;
  padding-left: 30px;
  padding-right: 30px;
  width: 100%;
  box-sizing: border-box;
  z-index: 1;
}
.weui-search-bar__input {
  height: 28px;
  line-height: 28px;
  font-size: 14px;
}
.weui-icon-clear {
  position: absolute;
  top: 0;
  right: 0;
  padding: 7px 8px;
  font-size: 0;
}
.weui-search-bar__label {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 2;
  border-radius: 3px;
  text-align: center;
  color: #9B9B9B;
  background: #FFFFFF;
  line-height: 28px;
}
.weui-search-bar__cancel-btn {
  margin-left: 10px;
  line-height: 28px;
  color: #09BB07;
  white-space: nowrap;
  font-size: 30rpx;
}

js文件

 showInput: function () {
    this.setData({
      inputShowed: true
    });
  },
  hideInput: function () {
    this.setData({
      inputVal: "",
      inputShowed: false
    });
    // getList(this);
  },
  clearInput: function () {
    this.setData({
      inputVal: ""
    });
    // getList(this);
  },
  inputTyping: function (e) {
    //搜索数据
    // getList(this, e.detail.value);
    this.setData({
      inputVal: e.detail.value
    });
  }