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我在我的应用程序中有一个情况，我需要上传几个文件，范围从 10-50+-（小尺寸，约 5 mb），并且如果需要还需要支持在后台继续。此时，我可以在应用程序处于前台时完美上传，但一旦应用程序进入后台，当前正在运行的上传将继续运行并在后台完成，但由于某种原因，其余操作永远不会被调用。

这是我的代码

后台队列初始化：

    private var _backgroundUploadQueue = OperationQueue()

后台队列设置：

    self._backgroundUploadQueue.maxConcurrentOperationCount = 4
    self._backgroundUploadQueue.name = "Background Queue"
    self._backgroundUploadQueue.qualityOfService = .background

创建操作：

private func _createUploadOperation(from action: S3UploadAction) -> AsyncBlockOperation {
    let operation = AsyncBlockOperation({ [weak self] operation in
        guard !operation.isCancelled else {
            operation.finish()
            return
        }
        self?._s3SinglePartUploader.upload(
            action: action,
            completion: { [weak self] result in
                self?._handleUploadCompletion(operation: operation, action: action, result: result)
            }
        )
        self?._singlePartUploadStarted(action: action)
    })
    operation.name = "\(action.recordingSetVersion)_\(action.partNumber)"

    return operation
}

添加操作：

private func _startBackgroundUploading() {
    for (_, actions) in self._uploadActions.enumerated() {
        for action in actions.value {
            let uploadOperation = self._createUploadOperation(from: action)
            self._backgroundUploadQueue.addOperation(uploadOperation)
        }
    }
}

在 AppDelegate 中，我添加了以下代码：

func application(
    _ application: UIApplication,
    handleEventsForBackgroundURLSession identifier: String,
    completionHandler: @escaping () -> Void
) {
    S3Uploader.shared.setBackgourndSessionCompletion(backgroundTaskCompletion: completionHandler)
    AWSS3TransferUtility.interceptApplication(
        application,
        handleEventsForBackgroundURLSession: identifier,
        completionHandler: completionHandler
    )
}
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