AFNetworking 3.0 上传图片 进度progress显示

我是一个初学者，希望大家不要喷，写这个都是因为我写的时候没有搜到,方便那些像我一样遇到这个困惑的初学者。

我的进度条是用MBProgressHUB写的 

MBProgressHUD * _hud;

_hud = [[MBProgressHUD alloc]initWithView:self.view];

_hud.labelText = @"正在上传";

_hud.mode = MBProgressHUDModeAnnularDeterminate;

[self.view addSubview:_hud];

3.0之后  有些许变化 http://www.jianshu.com/p/047463a7ce9b

progress部分反映了进度情况

上传图片是将数据流压缩了让后上传 ，也可不压缩

AFHTTPSessionManager * manager = [AFHTTPSessionManager manager];

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

        manager.responseSerializer = [AFHTTPResponseSerializer serializer]；

[_hud show:YES];

    [manager POST:@"Url 字符串" parameters:Dictionary constructingBodyWithBlock:^(id<AFMultipartFormData>  _Nonnull formData) {

        

        NSData * imgData = UIImageJPEGRepresentation(_imgV.image, 0.1);//0.1是把图片压缩  

        [formData appendPartWithFileData:imgData name:@"PHPhoto" fileName:@"phPhoto.jpg" mimeType:@"image/jpg/png/jpeg"];

        

    } progress:^(NSProgress * _Nonnull uploadProgress) {//进度 NSProgress 配合KVC来使用 反应进度情况

        

        [uploadProgress addObserver:self forKeyPath:@"fractionCompleted" options:NSKeyValueObservingOptionNew context:nil];

        

    } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {

        [_hud hide:YES];

        id root = [NSJSONSerialization JSONObjectWithData:responseObject options:NSJSONReadingAllowFragments error:nil];

        NSLog(@"%@",root);

        [self performSelectorOnMainThread:@selector(backToMain:) withObject:root waitUntilDone:YES];

        

    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {

        [_hud hide:YES];

        [self performSelectorOnMainThread:@selector(backToMain) withObject:nil waitUntilDone:YES];

        

    }];

#pragma mark -

#pragma mark 上传进度

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context

{

    if ([keyPath isEqualToString:@"fractionCompleted"] && [object isKindOfClass:[NSProgress class]]) {

        NSProgress *progress = (NSProgress *)object;

        _hud.progress = progress.fractionCompleted;

        

    }

}

#pragma mark -

这样就可以反映出 实时的上传进度了。