【flutter】上传

1、新建upload.dart

参考：https://www.cnblogs.com/yangyxd/p/9168271.html

import 'dart:io' ;
import 'dart:math' show Random;
import 'dart:async';
import 'package:http/http.dart' as Http;
/**
 * 请求响应数据
 */
class MsgResponse {
  int code; // 状态代码，0 表示没有错误
  Object data; // 数据内容，一般为字符串
  String errmsg; // 错误消息
  MsgResponse([this.code = 0, this.data = null, this.errmsg = ""]);
}

Map _makeHttpHeaders([String contentType,
    String accept,
    String token,
    String XRequestWith,
    String XMethodOverride]) {
  Map headers = new Map();
  int i = 0;
  if (contentType.isNotEmpty) {
    i++;
    headers["Content-Type"] = contentType;
  }
  if (accept.isNotEmpty) {
    i++;
    headers["Accept"] = accept;
  }
 /* if (token.isNotEmpty) {
    i++;
    headers["Authorization"] = "bearer " + token;
  }
*/
  if (XRequestWith.toString().isNotEmpty) {
    i++;
    headers["X-Requested-With"] = XRequestWith;
  }
  if (XMethodOverride.toString().isNotEmpty) {
    i++;
    headers["X-HTTP-Method-Override"] = XMethodOverride;
  }

  if (i == 0) return null;
  // print(headers.toString());
  return headers;
}



/** HTTP POST 上传文件 */
Future httpUploadFile(final String url, final File file, {
String accept = "*/*", String token, String field = "picture-upload", String file_contentType, // 默认为null，自动获取
}) async {
  try {
    List bytes = await file.readAsBytes();
    return await httpUploadFileData(url, bytes,
    accept: accept,
    token: token,
    field: field,
    file_contentType: file_contentType,
    filename: file.path);
  } catch (e) {
    return new MsgResponse(699, null, e.toString());
  }
}

/** HTTP POST 上传文件 */
Future httpUploadFileData(final String url, final List filedata, {
String accept = "*/*", String token, String field = "picture-upload", String file_contentType, // 默认为null，自动获取
String filename,
}) async {
//try {
List bytes = filedata;
var boundary = _boundaryString();
String contentType = 'multipart/form-data; boundary=$boundary';
Map headers =
_makeHttpHeaders(contentType, accept, token); //, "XMLHttpRequest");

// 构造文件字段数据
  print("$boundary");
String data =
'--$boundary\r\nContent-Disposition: form-data; name="$field"; ' +
'filename="${getFileFullName(filename)}"\r\nContent-Type: ' +
'${(file_contentType == null) ? getMediaType(getFileExt(filename).toLowerCase()): file_contentType}\r\n\r\n';
  print("$data");
var controller = new StreamController>(sync: true);
controller.add(data.codeUnits);
controller.add(bytes);
controller.add("\r\n--$boundary--\r\n".codeUnits);

controller.close();
bytes = await new Http.ByteStream(controller.stream).toBytes();
//print("bytes: \r\n" + UTF8.decode(bytes, allowMalformed: true));
Http.Response response =
  await Http.post(url, headers: headers, body: bytes);
  print(response.body);
  return MsgResponse(0, response.body);

  /*if (response.statusCode == 200) {
    return new MsgResponse(0, response.body);
  } else
    return new MsgResponse(response.statusCode, response.body);*/
  /*} catch (e) {
    return new MsgResponse(699, null, e.toString());
  }*/
}

/** 生成随机字符串 */
String randomStr([int len = 8, List chars = _BOUNDARY_CHARACTERS]) {
  var list = new List.generate(len, (index) => chars[_random.nextInt(chars.length)], growable: false);
  return new String.fromCharCodes(list);
}

const List _BOUNDARY_CHARACTERS = const [
  0x30,
  0x31,
  0x32,
  0x33,
  0x34,
  0x35,
  0x36,
  0x37,
  0x38,
  0x39,
  0x61,
  0x62,
  0x63,
  0x64,
  0x65,
  0x66,
  0x67,
  0x68,
  0x69,
  0x6A,
  0x6B,
  0x6C,
  0x6D,
  0x6E,
  0x6F,
  0x70,
  0x71,
  0x72,
  0x73,
  0x74,
  0x75,
  0x76,
  0x77,
  0x78,
  0x79,
  0x7A,
  0x41,
  0x42,
  0x43,
  0x44,
  0x45,
  0x46,
  0x47,
  0x48,
  0x49,
  0x4A,
  0x4B,
  0x4C,
  0x4D,
  0x4E,
  0x4F,
  0x50,
  0x51,
  0x52,
  0x53,
  0x54,
  0x55,
  0x56,
  0x57,
  0x58,
  0x59,
  0x5A
];
const int _BOUNDARY_LENGTH = 48;
final Random _random = new Random();
String _boundaryString() {
  var prefix = "---DartFormBoundary";
  var list = new List.generate(_BOUNDARY_LENGTH - prefix.length, (index) => _BOUNDARY_CHARACTERS[_random.nextInt(_BOUNDARY_CHARACTERS.length)], growable: false);
  return "$prefix${new String.fromCharCodes(list)}";
}

const mimeLists = {
  'css': 'text/css',
'html': 'text/html',
'js':'text/javascripte',
'xml': 'text/xml',
'gif': 'image/gif',
'jpg': 'image/jpeg',
'jpeg': 'image/jpeg',
'png': 'image/jpeg',
'json': 'application/json'
};
getMediaType(final String fileExt) {
  String Content = mimeLists["$fileExt"];
  if(Content.isEmpty){
    Content= 'text/plain';
  }
  return Content;
}
/*getMediaType(final String fileExt) {
  switch (fileExt) {
    case ".jpg":
    case ".jpeg":
    case ".jpe":
    return new MediaType("image", "jpeg");
    case ".png":
    return new MediaType("image", "png");
    case ".bmp":
    return new MediaType("image", "bmp");
    case ".gif":
    return new MediaType("image", "gif");
    case ".json":
    return new MediaType("application", "json");
    case ".svg":
    case ".svgz":
    return new MediaType("image", "svg+xml");
    case ".mp3":
    return new MediaType("audio", "mpeg");
    case ".mp4":
    return new MediaType("video", "mp4");
    case ".htm":
    case ".html":
    return new MediaType("text", "html");
    case ".css":
    return new MediaType("text", "css");
    case ".csv":
    return new MediaType("text", "csv");
    case ".txt":
    case ".text":
    case ".conf":
    case ".def":
    case ".log":
    case ".in":
    return new MediaType("text", "plain");
  }
  return null;
}*/
/**
 * 获取文件名
 */
String getFileFullName(filename){
  var index1 = filename.toString().lastIndexOf("/");
  if(index1.toString().isEmpty){
    index1=0;
  }
  var name = filename.substring(index1+1);
  //print(name);
  return name;
}
/**
 * 获取扩展名
 */
String getFileExt(filename){
  var index = filename.toString().lastIndexOf(".");
  var suffix = filename.toString().substring(index+1);
  //print(suffix);
  return suffix;
}

调用

import 'package:image_picker/image_picker.dart';//图片处理

//图库：ImageSource.gallery 相机：ImageSource.camera
Future getImage() async {
      var image = await ImagePicker.pickImage(source: ImageSource.gallery);
      if(image.toString().isEmpty){
        return null;
      }
      _uploadFile_vod(image);
      /*setState(() {
      imgList.add(image);
      });*/
    }
  _uploadFile_vod(image) async {
    //存取值需要
    //String url = "http://172.19.35.49:8080/wcms/front/announcement/uploadPhoto";

    String url = "http://172.19.35.37:8081/sgylbzj/front/jbinfo/uploadfile";
    print(image);
    //print(image.path);
    Future response = httpUploadFile(url, image);
    //print(response.toString());
  }

2、方法二

import 'dart:io';
import 'package:dio/dio.dart';

import 'package:flutter/material.dart';
import 'package:fluttertoast/fluttertoast.dart';//toast
import 'package:image_picker/image_picker.dart';//从相册里面选择图片或者拍照获取照片
class HeadImageUploadPage extends StatefulWidget {
  @override
  _HeadImageUploadPageState createState() => _HeadImageUploadPageState();
}

class _HeadImageUploadPageState extends State {
  File _image;

  Future getImage() async {
    var image = await ImagePicker.pickImage(source: ImageSource.gallery);
    _upLoadImage(image);//上传图片
    setState(() {
      _image = image;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Image Picker Example'),
      ),
      body: Center(
        child: _image == null
            ? Text('No image selected.')
            : Image.file(_image),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: getImage,
        tooltip: 'Pick Image',
        child: Icon(Icons.add_a_photo),
      ),
    );
  }
//上传图片
  _upLoadImage(File image) async {
    String path = image.path;
    var name = path.substring(path.lastIndexOf("/") + 1, path.length);
    FormData formData = new FormData.from({
      "file": new UploadFileInfo(new File(path), name)
    });
    Dio dio = new Dio();
    var respone = await dio.post("路径", data: formData);
    if (respone.statusCode == 200) {
      Fluttertoast.showToast(
          msg: "图片上传成功",
          gravity: ToastGravity.CENTER,
          textColor: Colors.grey);
    }
  }
}