1

我正在使用 AFNetworking 3.1.0 从 AWS S3 下载一些 pdf。唯一的问题是当文件被压缩时，下载进度块没有被调用。

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

NSURL *URL = [NSURL URLWithString:@"https://s3.amazonaws.com/awdtest/fullzip.pdf"];
NSURLRequest *request1 = [NSURLRequest requestWithURL:URL];

NSURLSessionDownloadTask *downloadTask1 = [manager downloadTaskWithRequest:request1 progress:^(NSProgress * _Nonnull downloadProgress)
{
    NSLog(@"Progress: %f", downloadProgress.fractionCompleted);
} 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)
{
    NSLog(@"File downloaded to: %@", filePath);
}];
[downloadTask1 resume];

响应标头：

HTTP/1.1 200 OK
x-amz-id-2: CW06YcgIycOHZQy8bCJrT3aNfhatM9pty1mOjgYHumjCxRmNAQ+jhJHRQwl7mDIaQeTHI0fyrnU=
x-amz-request-id: 105E010DECC91897
Date: Sat, 14 May 2016 09:26:38 GMT
Content-Encoding: gzip
Last-Modified: Sat, 14 May 2016 09:21:29 GMT
ETag: "88bbe0b318bf11dd56a31176d3384e78"
Accept-Ranges: bytes
Content-Type: application/pdf
Content-Length: 1243325
Server: AmazonS3

如果我使用非压缩文件，则会调用进度块：https ://s3.amazonaws.com/awdtest/full.pdf

响应标头：

HTTP/1.1 200 OK
x-amz-id-2: gFOVfhheaMdeJOBb+7H8oaXjLLeOqlQl616XnYx6C2Gj7PBVLKZ9kMIN2fJOrGBcSgQ/7nbQOc0=
x-amz-request-id: 26669D9B576E300A
Date: Sat, 14 May 2016 09:54:58 GMT
Last-Modified: Fri, 16 May 2014 05:42:35 GMT
ETag: "6f16d7e09023ce8b50fd67abba7825c4"
Accept-Ranges: bytes
Content-Type: application/pdf
Content-Length: 1411131
Server: AmazonS3

我将不胜感激任何帮助。

谢谢

4

1 回答 1

3

问题是当传输被压缩时，底层NSURLSession不知道传输的大小，所以当它调用带有更新的进度委托方法时，预期的大小是未知的。因此，完成百分比是未知的，因此很难更新NSProgress.

不过，您可以调用setDownloadTaskDidWriteDataBlockblock，并至少在它们进入时获取字节数。您会看到totalBytesExpectedToWrite为负数（即NSURLResponseUnknownLength），表明它不知道预期的字节数：

NSURLSessionDownloadTask *downloadTask1 = [manager downloadTaskWithRequest:request1 progress:^(NSProgress * _Nonnull downloadProgress) {
    NSLog(@"Progress: %f", downloadProgress.fractionCompleted);
} 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) {
    NSLog(@"File downloaded to: %@", filePath);
}];

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

[downloadTask1 resume];

这会产生：

2016-05-27 15:43:21.987 MyApp [41366:3034687] setDownloadTaskDidWriteDataBlock: 25510 25510 -1
2016-05-27 15:43:22.086 MyApp [41366:3034654] setDownloadTaskDidWriteDataBlock: 18934 44444 -1
2016-05-27 15:43:22.122 MyApp [41366:3034647] setDownloadTaskDidWriteDataBlock: 19184 63628 -1
...
2016-05-27 15:43:22.884 MyApp [41366:3034698] setDownloadTaskDidWriteDataBlock: 20742 1397325 -1
2016-05-27 15:43:22.885 MyApp [41366:3034637] setDownloadTaskDidWriteDataBlock: 13806 1411131 -1
2016-05-27 15:43:23.018 MyApp[41366:3034381] 文件下载到：file:///Users/.../D8735AFD-77F4-4496-B358-162467169C96/Documents/fullzip.pdf
于 2016-05-27T22:17:08.570 回答