AFnetworking网络请求

 出现下面错误
[error:Error Domain=NSCocoaErrorDomain Code=3840 "JSON text did not start with array or object and op](http://blog.csdn.net/air1120/article/details/50674212)

解决
manager.responseSerializer.acceptableContentTypes = [NSSetsetWithObjects:@"text/html",@"application/json",@"image/png", nil];
    
manager.responseSerializer = [AFHTTPResponseSerializer serializer];
manager.requestSerializer = [AFJSONRequestSerializer serializer];