Question

我正在尝试将一系列文件从iPhone上传到服务器，目的是即使应用程序处于后台或暂停，也会上传这些文件。

我正在使用NSURLSession及其系列API提供的后台传输。

奇怪的是它在2周前完全正常工作。如：

我会点击用户界面上的“上传”按钮
文件将开始在我的服务器上逐一显示
点击iPhone上的“主页”按钮，让应用程序进入后台
文件将继续上传到服务器，直到全部完成

最近几天，我一直在网络模块之外进行一些重构。几天前我再次尝试上传时，只要按下“主页”按钮，上面的步骤（3）。当我再次进入应用程序时，文件上传将停止。上传将恢复。

好像后台上传甚至无法正常工作（对于一个文件，更不用说多个文件了）。

我已多次运行代码，发现它的工作量约为1/50。但其他49次没有。我还检查了以前使用的代码版本（服务器+ iOS），它不再有效 - 或者说，工作很少变化（1/50）

经过rules进行背景转移和Lifecycle of URL Session多次以确保我遵守Apple建议的指导方针，我正在绞尽脑汁想知道什么破坏了，这令人难以置信这是多么不合逻辑 - 我怀疑它不是代码实现。

所以感谢任何帮助...

实施

1）在我的网络类（单身人士）的init方法中，我初始化NSURLSessionConfiguration和NSURLSession：

    urlSessionConfigUpload = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:kBACKGROUND_SESSION_CONFIG_ID];
    urlSessionConfigUpload.sessionSendsLaunchEvents = YES;
    urlSessionConfigUpload.discretionary = YES;
    urlSessionConfigUpload.HTTPMaximumConnectionsPerHost = 8;
    urlSessionConfigUpload.networkServiceType = NSURLNetworkServiceTypeBackground;
    urlSessionConfigUpload.HTTPShouldUsePipelining = NO; 
    urlSessionConfigUpload.allowsCellularAccess = NO;

    urlSession = [NSURLSession sessionWithConfiguration:urlSessionConfigUpload delegate:self delegateQueue:nil];

2）有一种方便的方法叫做实际上传。每个会话只有1个上传任务：

    NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url];
    [urlRequest setHTTPMethod:@"PUT"];
    [urlRequest addValue:@"keep-alive" forHTTPHeaderField:@"Connection"];
    [urlRequest addValue:contentType forHTTPHeaderField:@"Content-Type"];

    // NB: for upload task in the background, uploadTaskWithRequest:fromData (explicit construction of HTTP POST body) can’t be used,
    // must use uploadTaskWithRequest:fromFile (requiring HTTP PUT)
    NSURLSessionDataTask *uploadTask = [urlSession uploadTaskWithRequest:urlRequest fromFile:[NSURL fileURLWithPath:filePath]];
    [uploadTask resume];

3）在didCompleteWithError委托中，我检查是否所有文件都已上传，如果没有，请转到下一个文件 - GLOBAL.uploadQueue是我保留对我必须上传的所有文件的引用的地方，GLOBAL.uploadQueueIndexNextFile

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
        didCompleteWithError:(nullable NSError *)error
{
    if ((error == nil && (GLOBAL.uploadQueueIndexNextFile < GLOBAL.uploadQueue.count - 1)) {
        // Not on last file, increment counter, start upload of next file
        speedLoggerResult = [NSString stringWithFormat:@"Transferring %i of %i files", (GLOBAL.uploadQueueIndexNextFile + 1), GLOBAL.uploadQueue.count];
        GLOBAL.uploadQueueIndexNextFile++; 
        [GLOBAL.fileProcessor processNextFileInUploadQueue];
    }
}

processNextFileInUploadQueue将准备文件并调用上传的便捷方法（上面的（2））。

以下是穴居人调试的一些示例输出（对于文件2 - 4）。 请注意，只要应用进入后台，上传就会停止。

注意，我也等了超过下面输出中显示的10秒。最长的是我离开吃饭（30分钟），回来后上传结束了。一旦应用程序在后台，操作系统就永远不会选择它。

2016-02-21 05:53:01 +0000 | bkgd debug - about to start upload task | queueIndex: 2

2016-02-21 05:53:01 +0000 | in networking | totalBytesSent | 32768 of 233546 | queueIndex: 2

2016-02-21 05:53:01 +0000 | in networking | totalBytesSent | 65536 of 233546 | queueIndex: 2

2016-02-21 05:53:01 +0000 | in networking | totalBytesSent | 98304 of 233546 | queueIndex: 2

2016-02-21 05:53:01 +0000 | in networking | totalBytesSent | 131072 of 233546 | queueIndex: 2

2016-02-21 05:53:01 +0000 | in networking | totalBytesSent | 163840 of 233546 | queueIndex: 2

2016-02-21 05:53:01 +0000 | in networking | totalBytesSent | 196608 of 233546 | queueIndex: 2

2016-02-21 05:53:01 +0000 | in networking | totalBytesSent | 229376 of 233546 | queueIndex: 2

2016-02-21 05:53:01 +0000 | in networking | totalBytesSent | 233546 of 233546 | queueIndex: 2

2016-02-21 05:53:01 +0000 | in networking | didCompleteWithError | queueindex: 2

bkgd debug - processing next file

2016-02-21 05:53:02 +0000 | bkgd debug - about to start upload task | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 32768 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 65536 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 98304 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 131072 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 163840 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 196608 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 229376 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 262144 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 294912 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 327680 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 360448 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 387704 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 391392 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 393216 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 425984 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 458752 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 491520 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 524288 of 1231286 | queueIndex: 3

2016-02-21 05:53:02 +0000 | in networking | totalBytesSent | 538768 of 1231286 | queueIndex: 3

2016-02-21 05:53:03 +0000 | in networking | totalBytesSent | 541664 of 1231286 | queueIndex: 3

2016-02-21 05:53:03 +0000 | in networking | totalBytesSent | 550352 of 1231286 | queueIndex: 3

2016-02-21 05:53:03 +0000 | in networking | totalBytesSent | 553248 of 1231286 | queueIndex: 3

2016-02-21 05:53:03 +0000 | in networking | totalBytesSent | 557056 of 1231286 | queueIndex: 3

2016-02-21 05:53:03 +0000 | App went into background.

2016-02-21 05:53:03 +0000 | in networking | totalBytesSent | 564832 of 1231286 | queueIndex: 3

2016-02-21 05:53:03 +0000 | in networking | totalBytesSent | 567728 of 1231286 | queueIndex: 3

2016-02-21 05:53:03 +0000 | in networking | totalBytesSent | 582208 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 585104 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 589824 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 621680 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | App came into foreground. 

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 622592 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 655360 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 688128 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 720896 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 753664 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 786432 of 1231286 | queueIndex: 3

2016-02-21 05:53:14 +0000 | in networking | totalBytesSent | 819200 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 851968 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 884736 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 887632 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 893424 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 917504 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 939224 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 950272 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 970544 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 983040 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 1015808 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 1048576 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 1081344 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 1114112 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 1146880 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 1179648 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 1212416 of 1231286 | queueIndex: 3

2016-02-21 05:53:15 +0000 | in networking | totalBytesSent | 1231286 of 1231286 | queueIndex: 3

2016-02-21 05:53:16 +0000 | in networking | didCompleteWithError | queueindex: 3

bkgd debug - processing next file

2016-02-21 05:53:16 +0000 | bkgd debug - about to start upload task | queueIndex: 4

2016-02-21 05:53:16 +0000 | in networking | totalBytesSent | 32768 of 1278039 | queueIndex: 4

2016-02-21 05:53:16 +0000 | in networking | totalBytesSent | 65536 of 1278039 | queueIndex: 4

2016-02-21 05:53:16 +0000 | in networking | totalBytesSent | 98304 of 1278039 | queueIndex: 4

2016-02-21 05:53:16 +0000 | in networking | totalBytesSent | 131072 of 1278039 | queueIndex: 4

很高兴在这一点上尝试任何事情。谢谢！

编辑＃1

当后台上传工作时观察到操作系统调用了application:handleEventsForBackgroundURLSession:completionHandler:。当它不起作用时，永远不会发出回叫。

我不确定后台上传的先决条件是操作系统必须先杀死应用程序。如果是这样，在什么条件下会发生这种情况？我们可以提示吗？

如上所述，50次中有49次，操作系统会将应用程序保留在后台，并暂停上传。

Answer 1

有一件事想说清楚，你不能长时间在后台运行任何任务，因为Apple不允许你。只有在特殊情况下Apple才会考虑它。最好在Running background services in iOS

中解释

现在回到你的实施问题是它只适用于上传任务的后台，这是在应用程序处于活动状态且任务未完成时启动的。这就是50次尝试中有1次你看到任务在后台工作的原因。

现在要解决您的问题，您必须立即启动所有/一堆上传，以便如果应用程序进入后台，您的应用程序仍然可以上传文件。这个聪明的tutorial解释了与背景转移相关的不同案例。

您也可以试用AFNetworking多部分请求上传。

NSMutableURLRequest *request = [[AFHTTPRequestSerializer serializer] multipartFormRequestWithMethod:@"POST" URLString:@"http://example.com/upload" parameters:nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
        [formData appendPartWithFileURL:[NSURL fileURLWithPath:@"file://path/to/image.jpg"] name:@"file" fileName:@"filename.jpg" mimeType:@"image/jpeg" error:nil];
    } error:nil];

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

NSURLSessionUploadTask *uploadTask;
uploadTask = [manager
              uploadTaskWithStreamedRequest:request
              progress:^(NSProgress * _Nonnull uploadProgress) {
                  // This is not called back on the main queue.
                  // You are responsible for dispatching to the main queue for UI updates
                  dispatch_async(dispatch_get_main_queue(), ^{
                      //Update the progress view
                      [progressView setProgress:uploadProgress.fractionCompleted];
                  });
              }
              completionHandler:^(NSURLResponse * _Nonnull response, id  _Nullable responseObject, NSError * _Nullable error) {
                  if (error) {
                      NSLog(@"Error: %@", error);
                  } else {
                      NSLog(@"%@ %@", response, responseObject);
                  }
              }];

[uploadTask resume];

Answer 2

我的一个视频应用中也有同样的问题。这个问题发生在2月14日之后。我挖了很多，发现这发生在苹果改变了他们的全球证书之后。请检查此https://developer.apple.com/support/certificates/expiration/。解决方案是首先从钥匙串访问中撤消现有证书，然后添加新的开发/分发证书，新的应用程序ID和配置文件。它肯定会奏效。

Answer 3

我认为问题出在上传部分。您在完成上一个任务后启动下一个上载任务，而不是创建所有上载任务一次。在您的appDelegate中，将application:handleEventsForBackgroundURLSession:completionHandler:的完成处理程序存储为属性。使用NSURLSessionDelegate的{{1}} URLSessionDidFinishEventsForBackgroundURLSession:委托方法调用完成块。在拨打电话之前，请确保完成所有上传任务。本教程http://www.appcoda.com/background-transfer-service-ios7/很好地解释了下载任务。可能是您可以为上传任务应用相同的规则。

Answer 4

我遇到了类似的问题，文件正在上传。它在后台停了。

在审核文档和类似答案后花了几天时间。This solution worked for me

UIBackgroundTaskIdentifier是非常有用的重要财产之一。在app delegate类中创建此内容，并将其初始化为UIBackgroundTaskInvalid中的didFinishLaunchingWithOptions。

-

@interface AppDelegate ()

@property (atomic) UIBackgroundTaskIdentifier bgTask;
@property (nonatomic, weak) NSTimer *timer;

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.bgTask = UIBackgroundTaskInvalid;
    return YES;
}

应用程序正在将状态从Foreground转换为Background，反之亦然。我们需要确保在其相关的委托方法中检查此属性。

beginBackgroundTaskWithExpirationHandler 这对于在背景中实际启动后台任务非常重要。

-

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    self.bgTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        if (self.bgTask != UIBackgroundTaskInvalid) {
            [[UIApplication sharedApplication] endBackgroundTask:self.bgTask];
            self.bgTask = UIBackgroundTaskInvalid;
        }
    }];

    self.timer = [NSTimer scheduledTimerWithTimeInterval:10 target:self selector:@selector(startTracking) userInfo:nil repeats:YES];
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
    // invalidate the timer if still running

    [self.timer invalidate];

    // end the background task if still present

    if (self.bgTask != UIBackgroundTaskInvalid) {
        [[UIApplication sharedApplication] endBackgroundTask:self.bgTask];
        self.bgTask = UIBackgroundTaskInvalid;
    }
}

您可以调试实际设备中的代码，并在适当的网络条件下进行检查。

此外，您可以添加以下委托方法来跟踪bytesSent。

-

- (void)URLSession:(NSURLSession *)session
              task:(NSURLSessionTask *)task
   didSendBodyData:(int64_t)bytesSent
    totalBytesSent:(int64_t)totalBytesSent
totalBytesExpectedToSend:(int64_t)totalBytesExpectedToSend
{
    // Periodically informs the delegate of the progress of sending body content to the server.

    // Compute progress percentage
    float progress = (float)totalBytesSent / (float)totalBytesExpectedToSend;

    // Compute time executed so far
    NSDate *stopTime = [NSDate date];
    NSTimeInterval executionTime = [stopTime timeIntervalSinceDate:startTime];

    // Send info to console
    NSLog(@"%s bytesSent = %lld, totalBytesSent: %lld, totalBytesExpectedToSend: %lld, progress %.3f, time (s): %.1f", __PRETTY_FUNCTION__, bytesSent, totalBytesSent, totalBytesExpectedToSend, progress*100, executionTime);


}

我希望它对某人有帮助。

NSURLSession后台上传无效

实施

编辑＃1

4 个答案: