NSScreencast Episode #93 Background Transfers

Background Transfers - NSScreencast

画像のダウンロードをバックグラウンドで実行

• downloadTapped
  • if (!self.session) {
    • self.session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];
  • NSURLSessionDownloadTask *task = [self.session downloadTaskWithURL:imageUrl];
  • [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
  • [task resume];
• NSURLSessionDownloadDelegate
  • didFinishDownloadingToURL
  • didWriteData
  • didResumeAtOffset
  • URLSession didCompleteWithError
• notification
  • AppDelegate handleEventsForBackgroundURLSession
    • NSDictionary *userInfo = @{@"sessionIdentifier": identifier, @"completionHandler": completionHandler};
    • [[NSNotificationCenter defaultCenter] postNotificationName:@"BackgroundSessionUpdated"
• vc viewWillAppear
  • [[NSNotificationCenter defaultCenter] addObserver:self
    • selector:@selector(handleBackgroundSession:)
  • handleBackgroundSession notification
    • if ([notification.userInfo[@"sessionIdentifier"] isEqualToString:self.session.configuration.identifier]) {
      • self.backgroundCompletionHandler = notification.userInfo[@"completionHandler"];
• URLSessionDidFinishEventsForBackgroundURLSession
  • self.backgroundCompletionHandler();
  • self.backgroundCompletionHandler = nil;