如何在 AFNetworking 2.0 中获取下载进度？

Question

我正在使用 AFURLSessionManager 创建一个新的下载任务：

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];

文件可以正常下载，但是如何获得进度通知？

p 始终设置为零。我已经为此提交了issue。

我也尝试在管理器上调用setDownloadTaskDidWriteDataBlock，我确实在那里收到了进度通知，但我在文件下载后收到了所有进度通知。

好像这个区域在 AFNetworking 2.0 中还是有点问题

有什么想法吗？

Answer 1

对于带有进度状态的下载文件，请使用此代码

 NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];

NSURL *URL = [NSURL URLWithString:@"http://..."];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];


NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request progress:^(NSProgress * _Nonnull downloadProgress)
{
    NSLog(@"Progress: %f", downloadProgress.fractionCompleted);
    if (progressBlock) {
                    progressBlock(downloadProgress);
                }
} destination:^NSURL *(NSURL *targetPath, NSURLResponse *response)
{
    NSURL *documentsDirectoryURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil];
    return [documentsDirectoryURL URLByAppendingPathComponent:[response suggestedFilename]];
} completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error)
{
    if (response && successBlock) {
                    successBlock(response,filePath);
                }
    NSLog(@"File downloaded to: %@", filePath);
}];

[downloadTask resume];

Answer 2

Swift 的简单解决方案：

let sessionConfiguration = NSURLSessionConfiguration.defaultSessionConfiguration()
let sessionManager = AFURLSessionManager(sessionConfiguration: sessionConfiguration)
let request = NSURLRequest(URL: url)
let sessionDownloadTask = sessionManager.downloadTaskWithRequest(request, progress: nil, destination: { (url, response) -> NSURL in

            return destinationPath.URLByAppendingPathComponent(fileName) //this is destinationPath for downloaded file

            }, completionHandler: { response, url, error in

                //do sth when it finishes
        })

现在你有两个选择：

1. 使用UIProgressView 和setProgressWithDownloadProgressOfTask:

   progressView.setProgressWithDownloadProgressOfTask(sessionDownloadTask, animated: true)
   

2. 使用AFURLSessionManager 和setDownloadTaskDidWriteDataBlock:

   sessionManager.setDownloadTaskDidWriteDataBlock { session, sessionDownloadTask, bytesWritten, totalBytesWritten, totalBytesExpectedToWrite in
   
       let progress = Float(totalBytesWritten)/Float(totalBytesExpectedToWrite)
           //do sth with current progress
   }
   

最后不要忘记：

sessionDownloadTask.resume()

Answer 3

您应该使用 KVO 观察 NSProgress 对象的 fractionCompleted 属性：

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

您还可以使用AFURLSessionManager（AFHTTPSessionManager 继承自该方法）的setDownloadTaskDidWriteDataBlock: 方法来设置接收下载进度更新的块。

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

这种 AFNetworking 方法将 URLSession:downloadTask:didWriteData:totalBytesWritten:totalBytesExpectedToWrite: 方法从 NSURLSessionDownloadDelegate 协议映射到更方便的阻塞机制。

顺便说一句，Apple 的 KVO 实现被严重破坏。我建议使用更好的实现，例如 Mike Ash 提出的MAKVONotificationCenter。如果您有兴趣了解为什么 Apple 的 KVO 被破坏，请阅读 Mike Ash 的 Key-Value Observing Done Right。

Answer 4

我遇到了类似的问题，并找到了解决方案。

查看以下链接： http://cocoadocs.org/docsets/AFNetworking/2.0.1/Categories/UIProgressView+AFNetworking.html

#import <AFNetworking/UIKit+AFNetworking.h>

并使用 UIProgressView 可用的其他方法

setProgressWithDownloadProgressOfTask:animated:

我是怎么做到的：

NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request  progress:nil destination:^NSURL *(NSURL *targetPath, NSURLResponse *response){
    NSURL *documentsDirectoryPath = [NSURL fileURLWithPath:[NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask, YES) firstObject]];
    return [documentsDirectoryPath URLByAppendingPathComponent:[targetPath lastPathComponent]];
} completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error){
    NSLog(@"File downloaded to: %@", filePath);

}];

[self.progressView setProgressWithDownloadProgressOfTask:downloadTask animated:YES];
[downloadTask resume];