基于taro实现小程序selct选择框

您提到的小程序 `select` 选择框可以通过在小程序页面中使用 `picker` 组件来实现。具体的实现步骤如下：

1. 在小程序页面的 `json` 文件中添加 `picker` 组件，设置 `mode` 属性为 `selector`，设置 `range` 属性为选项数组。

   {
     "usingComponents": {
       "picker": "/miniprogram_npm/@tarojs/components/dist/taro-components/taro-components.esm"
     },
     "navigationBarTitleText": "首页",
     "navigationBarBackgroundColor": "#fff",
     "navigationBarTextStyle": "black",
     "enablePullDownRefresh": true,
     "backgroundTextStyle": "dark",
     "backgroundColor": "#F5F5F5",
     "usingComponents": {},
     "component": true,
     "disableScroll": true,
     "navigationStyle": "custom",
     "window": {
       "backgroundTextStyle": "light",
       "navigationBarBackgroundColor": "#fff",
       "navigationBarTitleText": "WeChat",
       "navigationBarTextStyle": "black"
     },
     "usingComponents": {
       "picker": "/miniprogram_npm/@tarojs/components/dist/taro-components/taro-components.esm"
     },
     "disableScroll": true,
     "navigationBarTitleText": "首页",
     "enablePullDownRefresh": true,
     "backgroundTextStyle": "dark",
     "backgroundColor": "#F5F5F5",
     "usingComponents": {}
   }

2. 在小程序页面的 `js` 文件中添加以下代码，定义选项数组和当前选中的索引。

   import Taro, { Component } from '@tarojs/taro'
   import { View } from '@tarojs/components'
   
   class Index extends Component {
     config = {
       navigationBarTitleText: '首页'
     }
   
     state = {
       options: ['选项1', '选项2', '选项3', '选项4', '选项5'],
       selectedIndex: 0
     }
   
     onPickerChange = e => {
       const { value } = e.detail
       this.setState({
         selectedIndex: value
       })
     }
   
     render() {
       const { options, selectedIndex } = this.state
       return (
         <View className='index'>
           <picker mode='selector' range={options} value={selectedIndex} onChange={this.onPickerChange}>
             <View className='picker'>
               <View className='picker-text'>{options[selectedIndex]}</View>
               <View className='picker-icon' />
             </View>
           </picker>
           <View className='content'>这是首页</View>
         </View>
       )
     }
   }
   
   export default Index

3. 在小程序页面的 `scss` 文件中添加以下样式，设置 `picker` 组件的位置和样式。

   .picker {
     display: flex;
     justify-content: space-between;
     align-items: center;
     padding: 10px;
     background-color: #fff;
     border-bottom: 1px solid #eee;
     font-size: 14px;
     color: #333;
   }
   
   .picker-text {
     flex: 1;
     margin-right: 10px;
   }
   
   .picker-icon {
     width: 10px;
     height: 10px;
     border-top: 1px solid #333;
     border-right: 1px solid #333;
     transform: rotate(45deg);
   }

通过以上步骤，即可实现小程序 `select` 选择框的效果。需要注意的是，`picker` 组件在不同的系统和设备上可能会出现样式问题，需要进行适当的调整。