flutter 接入阿里云OSS

之前因为使用正常文件上传，用户多时拥堵无法正常上传，因此接入阿里OSS 来解决这个问题。本来打算整原生那块，看了下比较麻烦，用flutter dio 直接请求oss 完成

1.上传用到了image_picker 插件。这个比较简单了。

//要上传的文件，此处为从相册选择照片
File imageFile = await ImagePicker.pickImage(source: ImageSource.gallery);

2.阿里oss 配置以及相关处理String accesskey = '后台返回的AccessKeySecret'; 这个比较重要要用secret    print(accesskey);    //验证文本域

    String policyText =
        '{"expiration": "2020-01-01T12:00:00.000Z","conditions": [["content-length-range", 0, 1048576000]]}';
    //进行utf8编码
    List<int> 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<int> policy = utf8.encode(policy_base64);
    //进行utf8 编码
    List<int> key = utf8.encode(accesskey);
    //通过hmac,使用sha1进行加密
    List<int> signature_pre = new 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);
    //dio的请求配置，这一步非常重要！
    BaseOptions options = new BaseOptions();
    options.responseType = ResponseType.plain;  这个后台返回值dio 默认json 要设置为普通文本
//创建dio对象
    Dio dio = new Dio(options);
    //文件名
    String fileName = _image.path
        .substring(_image.path.lastIndexOf("/") + 1, _image.path.length);
//    生成uuid
    String uuid1 = uuid.v1();
    //创建一个formdata，作为dio的参数
    FormData data = new FormData.from({
      'Filename': 'img',
      'key': 'images/work/${uuid1}/img.' + fileName.split('.')[1],   //设置阿里oss 路径 不写就是默认根目录
      'policy': policy_base64,
      'OSSAccessKeyId': 'OSSAccessKeyId', 
'success_action_status': '200', //让服务端返回200，不然，默认会返回204 
'signature': signature, 
'file': new UploadFileInfo(new File(_image.path), "imageFileName") 
}); // print(_image.path); //  
Response response; // Dio dio = new Dio(); // dio.options.baseUrl = DioUtil.API_PREFIX; 
var loginData = SpUtil.getObject('loginData'); if (loginData != null) { var token = '${loginData['token_type']} ${loginData['access_token']}'; 
dio.options.headers['Authorization'] = token; } //设置token
if (Platform.isAndroid) { dio.options.headers['Client-Type'] = 'android'; } else { dio.options.headers['Client-Type'] = 'ios'; } 
dio.options.headers['Accept'] = 'application/json'; dio.options.headers['Content-Type'] = 'application/json'; print(dio.options.headers); 
setState(() { showPro = true; });
 try { 
response = await dio .post('http://lncc-public.oss-accelerate.aliyuncs.com', data: data, 
onSendProgress: (int sent, int total) {  //进度设置
print("上传进度=======$sent $total"); 
if (sent == total) { print('百分之百'); 
setState(() { showPro = false; Progress = 100; }); 
var obj = {'id': 'temp', 'work_url': _image.path}; 
uploadFileInfo.add(obj); 
audioCache.play('collect/upload_01/00001.mp3', volume: 0.5); 
setState(() { ifshow = 1.0;
//动画以及声音设置
}); 

FlutterTimer.startTimerChanged( 
duration: _assetList.length, period: periodMilli, fromEnd: false, counting: _animing, end: null); 
Future.delayed(Duration(seconds: 4), () { 
print('三秒后关闭'); 
FlutterTimer(context).release(); 
setState(() { 
ifshow = 0; Progress = 0; 
}); 
}); 
} else { 
setState(() { 
Progress = int.parse(((sent / total) * 100).toStringAsFixed(0)); print(Progress); }); } 
}); 
var result = response.statusCode; 
if(result==200){ 
print(result); 
var upurl = 'https://public-statics.lnart.com/images/work/${uuid1}/img.'+ fileName.split('.')[1]; print(upurl);  //将上传oss的路径上传到自己的服务器
setState(() { showPro = false; }); 
} 
} on DioError catch (e) { 
print(e.message); 
print(e.response.data); 
print(e.response.headers); 
print(e.response.request); 
}