• @param fileType 文件类型例如jpg,mp4等
• @param callback 回调函数我这里用于传cancelToken，方便后期关闭请求
• @param onSendProgress 上传的进度事件
  */

static Future upload({ File file , String rootDir = ‘moment’, String fileType, Function callback, Function onSendProgress}) async {
String policyText = ‘{“expiration”: “KaTeX parse error: Expected '}', got 'EOF' at end of input: …: [{"bucket": "bucket” },[“content-length-range”, 0, 1048576000]]}’;

// 获取签名
String signature = getSignature(policyText);

BaseOptions options = new BaseOptions();
options.responseType = ResponseType.plain;

//创建dio对象
Dio dio = new Dio(options);
// 生成oss的路径和文件名我这里目前设置的是moment/20201229/test.mp4
String pathName = ‘$rootDir/${getDate()}/$getRandom(12).${fileType == null ? getFileType(file.path) : fileType}’;

// 请求参数的form对象
FormData data = new FormData.fromMap({
‘key’: pathName,
‘policy’: getSplicyBase64(policyText),
‘OSSAccessKeyId’: ossAccessKeyId,
‘success_action_status’: ‘200’, //让服务端返回200，不然，默认会返回204
‘signature’: signature,
‘contentType’: ‘multipart/form-data’,
‘file’: MultipartFile.fromFileSync(file.path),
});

Response response;
CancelToken uploadCancelToken = CancelToken();
callback ?? callback(uploadCancelToken);

try {
// 发送请求
response = await dio.post(url, data: data, cancelToken: uploadCancelToken, onSendProgress: (int count, int data) {
onSendProgress(count, data);
});
// 成功后返回文件访问路径
return ‘$url/$pathName’;
} catch(e) {
throw(e.message);
}

}

/*

• 生成固定长度的随机字符串
• /
  static String getRandom(int num) {
  String alphabet = ‘qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM’;
  String left = ‘’;
  for (var i = 0; i < num; i++) {
  // right = right + (min + (Random().nextInt(max - min))).toString();
  left = left + alphabet[Random().nextInt(alphabet.length)];
  }
  return left;
  }
  /
• 根据图片本地路径获取图片名称
• /
  static String getImageNameByPath(String filePath) {
  // ignore: null_aware_before_operator
  return filePath?.substring(filePath?.lastIndexOf(“/”)+1,filePath?.length);
  }
  /*
• 获取文件类型
  */
  static String getFileType(String path) {
  print(path);
  List array = path.split(‘.’);
  return array[array.length -1];
  }
  /// 获取日期
  static String getDate() {
  DateTime now = DateTime.now();
  return ‘$now.year${now.month}${now.day}’;
  }

// 获取plice的base64
static getSplicyBase64(String policyText) {
//进行utf8编码
List policyText_utf8 = utf8.encode(policyText);
//进行base64编码
String policy_base64 = base64.encode(policyText_utf8);
return policy_base64;
}

/// 获取签名
static String getSignature(String policyText) {
//进行utf8编码
List policyText_utf8 = utf8.encode(policyText);
//进行base64编码
String policy_base64 = base64.encode(policyText_utf8);
//再次进行utf8编码
List policy = utf8.encode(policy_base64);
//进行utf8 编码
List key = utf8.encode(ossAccessKeySecret);
//通过hmac,使用sha1进行加密
List signature_pre = Hmac(sha1, key).convert(policy).bytes;
//最后一步，将上述所得进行base64 编码
String signature = base64.encode(signature_pre);
return signature;
}
}

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