通过 Dio 我们可以将文件上传到阿里OSS。

    1. import 'dart:convert';
    2. import 'dart:io';
    3. import 'package:crypto/crypto.dart';
    4. import 'package:dio/dio.dart';
    5. import 'package:uuid/uuid.dart';
    7. class HttpUtil {
    8.   static HttpUtil instance;
    9.   Dio dio;
    10.   BaseOptions options;
    12.   // oss相关参数
    13.   static String ossPath = 'https://xxx.oss-cn-shenzhen.aliyuncs.com';
    14.   static String accesskeyId= 'your accesskeyId';
    15.   static String accesskeySecret= 'your accesskeySecret';
    16.   static String uploadBaseUrl = 'test/flutter';
    17.   static String policyText = '{"expiration": "2020-01-01T12:00:00.000Z","conditions": [["content-length-range", 0, '
    18.       '1048576000]]}'; // 验证文本域
    20.   // 签名相关
    21.   static List<int> policyText_utf8 = utf8.encode(policyText); // 进行utf8编码
    22.   static String policy_base64 = base64.encode(policyText_utf8); // 进行base64编码
    23.   static List<int> policy = utf8.encode(policy_base64); // 再次进行utf8编码
    24.   static List<int> key = utf8.encode(accesskeySecret); // 进行utf8 编码
    25.   static List<int> signature_pre  = new Hmac(sha1, key).convert(policy).bytes; // 通过hmac,使用sha1进行加密
    26.   String signature = base64.encode(signature_pre); // 最后一步，将上述所得进行base64 编码
    28.   HttpUtil() {
    29.     options = BaseOptions(
    30.       connectTimeout: 10000,
    31.       receiveTimeout: 10000,
    32.       headers: {},
    33.     );
    34.     dio = new Dio(options);
    35.   }
    37.   oss(File file) async { // 接受一个 File 类型的参数
    38.     var ext = file.path.split('.').last; // 获取文件扩展名
    39.     var userId = (await Storage.get('userInfo'))['id'].toString();
    40.     var now = (new DateTime.now()).toString();
    41.     var uuid = new Uuid();
    42.     var filename = uuid.v5(Uuid.NAMESPACE_URL, now + userId); // 通过当前时间和userId生成uuid
    44.     // 构建 FormData
    45.     FormData data = new FormData.from({
    46.       'Filename': '文件名，随意',
    47.       'key' : "$uploadBaseUrl/$filename.$ext",
    48.       'policy': policy_base64,
    49.       'OSSAccessKeyId': accesskeyId,
    50.       'success_action_status' : '200', // 让服务端返回200，不然，默认会返回204
    51.       'signature': signature,
    52.       'file': new UploadFileInfo(file, "imageFileName")
    53.     });
    55.     try {
    56.       Response response = await dio.post(ossPath, data: data);
    57.       var uploadPath = "$ossPath/$uploadBaseUrl/$filename.$ext";
    58.       print("上传成功: $uploadPath");
    59.       return uploadPath; // 返回上传路径
    60.     } on DioError catch(e) {
    61.       print("上传失败: $e");
    62.     }
    63.   }
    64. }

    使用的时候：

    1. Future getImage() async {
    2.   try {
    3.     File image = await ImagePicker.pickImage(source: ImageSource.gallery);
    4.     var uploadPath = await HttpUtil().oss(image);
    5.     print(uploadPath);
    6.   } catch (e) {}
    7. }

    这里, 使用了 ImagePicker 从相册或拍照获取文件, 需要引入包：

    1. import 'package:image_picker/image_picker.dart';

    本文使用到的一些依赖：

    1. dependencies:
    2.   dio: ^2.1.0
    3.   image_picker: ^0.6.1+4
    4.   crypto: ^2.1.3
    5.   uuid: ^2.0.1