如何在AFNetworking 2.0中获得下载进度？ [英] How to get download progress in AFNetworking 2.0?

问题描述

我正在使用AFURLSessionManager创建新的下载任务：

I am using AFURLSessionManager to create a new download task:

AFURLSessionManager* manager = ...

NSProgress* p = nil;
NSURLSessionDownloadTask* downloadTask =
        [manager downloadTaskWithRequest:request
                                 progress:&p
                              destination:^NSURL*(NSURL* targetPath, NSURLResponse* response) {...}
                        completionHandler:^(NSURLResponse* response, NSURL* filePath, NSError* error) {...}
        ];
[downloadTask resume];

文件下载得很好，但是，如何获取进度通知？

The file gets downloaded fine, however, how do I get progress notifications?

p 始终设为nil。我已经为此提交了问题。

p is always set to nil. I've filed an issue for that.

我也尝试在经理上调用 setDownloadTaskDidWriteDataBlock ，我确实在那里得到了进度通知但我收到的所有这些都是之后 em>该文件已被下载。

I've also tried to call setDownloadTaskDidWriteDataBlock on the manager, and I do get progress notifications there but I receive them all grouped together after the file has been downloaded.

似乎这个区域在AFNetworking 2.0中仍然有点儿错误

Seems like this area is still a bit buggy in AFNetworking 2.0

有什么想法吗？

推荐答案

你应该观察<你的 fractionCompleted 属性code> NSProgress 使用KVO的对象：

You should observe the fractionCompleted property of your NSProgress object using KVO:

NSURL *url = [NSURL URLWithString:@"http://www.hfrmovies.com/TheHobbitDesolationOfSmaug48fps.mp4"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFHTTPSessionManager *session = [AFHTTPSessionManager manager];
NSProgress *progress;
NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithRequest:request progress:&progress destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
    // …
} completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
    [progress removeObserver:self forKeyPath:@"fractionCompleted" context:NULL];
    // …
}];

[downloadTask resume];
[progress addObserver:self
            forKeyPath:@"fractionCompleted"
               options:NSKeyValueObservingOptionNew
               context:NULL];

然后添加观察者方法：

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqualToString:@"fractionCompleted"]) {
        NSProgress *progress = (NSProgress *)object;
        NSLog(@"Progress… %f", progress.fractionCompleted);
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

当然，你应该检查 keyPath 和/或 object 参数，以确定这是否是您要观察的对象/属性。

Of course, you should check keyPath and/or object parameters to decide if that's the object/property you want to observe.

您还可以使用 AFURLSessionManager 中的 setDownloadTaskDidWriteDataBlock：方法（从中 AFHTTPSessionManager inherits）设置一个接收下载进度更新的块。

You can also use the setDownloadTaskDidWriteDataBlock: method from AFURLSessionManager (from which AFHTTPSessionManager inherits) to set a block for receiving download progress updates.

[session setDownloadTaskDidWriteDataBlock:^(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, int64_t bytesWritten, int64_t totalBytesWritten, int64_t totalBytesExpectedToWrite) {
    NSLog(@"Progress… %lld", totalBytesWritten);
}];

此AFNetworking方法映射 URLSession：downloadTask：didWriteData：totalBytesWritten：totalBytesExpectedToWrite： 方法从 NSURLSessionDownloadDelegate 协议到更方便的块机制。

This AFNetworking method maps the URLSession:downloadTask:didWriteData:totalBytesWritten:totalBytesExpectedToWrite: method from NSURLSessionDownloadDelegate protocol to a more convenient block mechanism.

BTW，Apple的KVO实施严重受损。我建议使用更好的实现，例如Mike Ash在 MAKVONotificationCenter 中提出的实现。如果您有兴趣阅读为什么Apple的KVO坏了，请阅读 Key-Value Observing Right Right Mike Ash。

BTW, Apple's KVO implementation is severely broken. I recommend using a better implementation like the one proposed by Mike Ash with MAKVONotificationCenter. If you are interested in reading why Apple's KVO is broken, read Key-Value Observing Done Right by Mike Ash.

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