flutter上传图片到华为云obs

import 'dart:io';

import 'package:dio/dio.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_screenutil/screenutil.dart';
import 'package:image_pickers/Media.dart';
import 'package:oktoast/oktoast.dart';
import 'package:visitormachine/widget/load_image.dart';
import 'package:visitormachine/widget/my_app_bar.dart';
import 'package:image_pickers/image_pickers.dart';
import 'package:http_parser/http_parser.dart';
import 'package:crypto/crypto.dart';
///这里用来进行Base64编码，UTF-8编码的
import 'dart:convert';
///这里用来获取文件file的文件名称的
import 'package:path/path.dart';
///HMAC-SHA1加密用的（这个是第三方库需要依赖）
import 'package:crypto/crypto.dart';


class TrainPhotographPage extends StatefulWidget {
  TrainPhotographPage({Key key}) : super(key: key);

  @override
  _TrainPhotographP