一个好的问题总是有多个答案，为了减少和帮助你选择正确的答案，在这里我也加入了我自己的答案。我已经测试过了，工作正常。

AFHTTPRequestOperationManager *manager = [[AFHTTPRequestOperationManager alloc] initWithBaseURL:[NSURL URLWithString:@"http://www.yourdomain.com/appname/data/ws/index.php/user/login/"]];
manager.requestSerializer = [AFJSONRequestSerializer serializer];
manager.responseSerializer = [AFHTTPResponseSerializer serializer];

[manager POST:@"POST" parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {
    NSString *json = [[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding];
    NSLog(@"%@", json);
    //Now convert json string to dictionary.
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"%@", error.localizedDescription);
}];

这意味着您的服务器正在发送“text/html”而不是已经支持的类型。 我的解决方案是添加“文本/html”到acceptableContentTypes设置在AFURLResponseSerialization类。只需搜索“acceptableContentTypes”，并手动添加@“text/html”到集合。

当然，理想的解决方案是改变从服务器发送的类型，但为此您必须与服务器团队讨论。

我从Swift代码库中使用AFNetworking工作时遇到了类似的问题，所以我只是把这个留在远程情况下，有人像我一样不幸，必须在这样的设置中工作。如果你是，我觉得你，伙计，坚强点!

操作由于“不可接受的内容类型”而失败，尽管我实际上设置了一个包含有问题的内容类型值的Set acceptableContentTypes。

我的解决方案是调整Swift代码，使其更适合Objective-C，我想:

serializer.acceptableContentTypes = NSSet(array: ["application/xml", "text/xml", "text/plain"]) as Set<NSObject>

 UIImage *image = [UIImage imageNamed:@"decline_clicked.png"];
NSData *imageData = UIImageJPEGRepresentation(image,1);


NSString *queryStringss = [NSString stringWithFormat:@"http://119.9.77.121/lets_chat/index.php/webservices/uploadfile/"];
queryStringss = [queryStringss stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
manager.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/html"];

[MBProgressHUD showHUDAddedTo:self.view animated:YES];


[manager POST:queryStringss parameters:nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData)
 {


     [formData appendPartWithFileData:imageData name:@"fileName" fileName:@"decline_clicked.png" mimeType:@"image/jpeg"];



 }
      success:^(AFHTTPRequestOperation *operation, id responseObject)
 {



    NSDictionary *dict = [responseObject objectForKey:@"Result"];

    NSLog(@"Success: %@ ***** %@", operation.responseString, responseObject);
    [MBProgressHUD hideAllHUDsForView:self.view animated:YES];


 }
      failure:^(AFHTTPRequestOperation *operation, NSError *error)
 {
     [MBProgressHUD hideAllHUDsForView:self.view animated:YES];
     NSLog(@"Error: %@ ***** %@", operation.responseString, error);
 }];

一个简单的方法来启用接收“文本/纯”内容类型:

manager.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/plain"];

类似地，如果你希望启用"text/html"内容类型:

manager.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/html"];

将我的RequestOperationManager ResponseSerializer设置为HTTPResponseSerializer修复了这个问题。

objective - c

manager.responseSerializer = [AFHTTPResponseSerializer serializer];

斯威夫特

manager.responseSerializer = AFHTTPResponseSerializer()

做这个更改意味着我不需要为我发出的每个请求添加acceptableContentTypes。