(1)通过长按事件获取到照片路径(或ref获取dom对象)
		因通e无法获取到src属性,固添加自定义属性为照片url地址
		<Image className='m-i' data-url={'xx.jpg'} onLongPress={this._LongPress}  src='xx.jpg'/>
	
	(2)onLongPress长按事件中获取到照片url
		e.target.dataset.url
	
	(3)通过Taro.getImageInfo获取到照片的本地路径
		Taro.getImageInfo({
			src:'图片的路径，可以是相对路径、临时文件路径、存储文件路径、网络图片路径',
			success(res)
			{
				res.path获取到照片的本地路径
			}
			
		})
	
	(4)通过Taro.saveImageToPhotosAlbum,将照片保存到系统相册
		Taro.saveImageToPhotosAlbum({
			filePath:'图片文件路径，可以是临时文件路径或永久文件路径，不支持网络图片路径',
			success(res)
			{
				...
			}
		})

保存图片底部面报提示、图片授权、以及未授权引导授权、保存成功提示完整代码:

import Taro from '@tarojs/taro'
import {View,Text,Image,OpenData,} from '@tarojs/components'
import React,{Component} from 'react'
import {connect} from 'react-redux'

import './index.less'

import Avator from './child/avator'
import Card from './child/card'

class Mine extends Component{

    componentDidMount()
    {
    }

    //长按保存图片到系统相册底部面报提示
    _LongPress=(e)=>{
        let that=this;
        Taro.showActionSheet({
            itemList:['保存到系统相册','取消'],
            success(res)
            {   
                //保存到系统相册
                if(res.tapIndex==0)
                {
                    that._saveImageAuthorize(e.target.dataset.url)
                }else{
                    //取消保存
                }
            }
        })
    }

    //保存到系统相册授权
    _saveImageAuthorize(url)
    {
        // console.log(url);
        let that=this;
        Taro.getSetting({
            success(res)
            {
                //未授权
                if(!res.authSetting['scope.writePhotosAlbum'])
                {
                    Taro.authorize({
                        scope: 'scope.writePhotosAlbum',
                        success: function () {
                          //同意授权
                          that._saveImage(url);
                        },
                        //拒绝授权引导手动开启
                        fail()
                        {
                            Taro.showModal({
                                title:'提示',
                                confirmText:'确认',
                                cancelText:'取消',
                                content:'是否开启相册权限',
                                success(res)
                                {
                                    if(res.confirm)
                                    {
                                      Taro.openSetting();
                                    }else if(res.cancel)
                                    {
                                      
                                    }
                                }

                            })
                        }
                    })
                //已授权
                }else{
                    that._saveImage(url);
                }
            }
        })

    }

    //将照片保存到系统相册
    _saveImage(url)
    {
        console.log(url);
        Taro.getImageInfo({
            src:url,
            success(res)
            {
                Taro.saveImageToPhotosAlbum({
                    filePath:res.path,
                    success()
                    {
                        Taro.showToast({
                            title:'已保存到系统相册'
                        })
                    }
                })
            }
        });
    }

    render()
    {
        const {name,avator} = this.props;
        return(

            <View className='m-c'>
                <Image className='m-i' data-url={'https://dss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=3213420747,3920605119&fm=26&gp=0.jpg'} onLongPress={this._LongPress}  src='https://dss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=3213420747,3920605119&fm=26&gp=0.jpg'/>
                {/* <OpenData type='userAvatarUrl'/> */}
            </View>
        )
    }
}

const mapStateToProps=(state)=>{
    return{
        name:state.user.username,
        avator:state.user.avator
    }
}

export default connect(mapStateToProps)(Mine)