<key>UIBackgroundModes</key>
<array><string>fetch</string>
</array>

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{//UIApplicationBackgroundFetchIntervalMinimum表示尽可能频繁去获取，如果需要指定至少多少时间更新一次就需要给定一个时间值[application setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];return YES; }

- (void) application:(UIApplication *)application
performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfiguration]; NSURL *url = [[NSURL alloc] initWithString:@"http://yourserver.com/data.json"]; NSURLSessionDataTask *task = [session dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { if (error) { completionHandler(UIBackgroundFetchResultFailed); return; } // 解析响应/数据以决定新内容是否可用 BOOL hasNewData = ... if (hasNewData) { completionHandler(UIBackgroundFetchResultNewData); } else { completionHandler(UIBackgroundFetchResultNoData); } }]; // 开始任务 [task resume]; }

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{NSLog(@"Launched in background %d", UIApplicationStateBackground == application.applicationState); return YES; }

{"aps" : {"content-available" : 1 }, "content-id" : 42 }

- (void)application:(UIApplication *)applicationdidReceiveRemoteNotification:(NSDictionary *)userInfofetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{NSLog(@"Remote Notification userInfo is %@", userInfo); NSNumber *contentID = userInfo[@"content-id"]; // 根据 content ID 进行操作 completionHandler(UIBackgroundFetchResultNewData); }

- (NSURLSession *)backgroundURLSession
{static NSURLSession *session = nil;static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ NSString *identifier = @"io.objc.backgroundTransferExample"; NSURLSessionConfiguration* sessionConfig = [NSURLSessionConfiguration backgroundSessionConfiguration:identifier]; session = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:[NSOperationQueue mainQueue]]; }); return session; } - (void) application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler { NSLog(@"Received remote notification with userInfo %@", userInfo); NSNumber *contentID = userInfo[@"content-id"]; NSString *downloadURLString = [NSString stringWithFormat:@"http://yourserver.com/downloads/%d.mp3", [contentID intValue]]; NSURL* downloadURL = [NSURL URLWithString:downloadURLString]; NSURLRequest *request = [NSURLRequest requestWithURL:downloadURL]; NSURLSessionDownloadTask *task = [[self backgroundURLSession] downloadTaskWithRequest:request]; task.taskDescription = [NSString stringWithFormat:@"Podcast Episode %d", [contentID intValue]]; //执行resume保证开始了任务 [task resume]; completionHandler(UIBackgroundFetchResultNewData); }

#Pragma Mark - NSURLSessionDownloadDelegate- (void) URLSession:(NSURLSession *)sessiondownloadTask:(NSURLSessionDownloadTask *)downloadTaskdidFinishDownloadingToURL:(NSURL *)location
{NSLog(@"downloadTask:%@ didFinishDownloadingToURL:%@", downloadTask.taskDescription, location); // 必须用 NSFileManager 将文件复制到应用的存储中，因为临时文件在方法返回后会被删除 // ... // 通知 UI 刷新 } - (void) URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes { } - (void) URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite { }

- (void) application:(UIApplication *)applicationhandleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)())completionHandler
{// 你必须重新建立一个后台 seesiong 的参照// 否则 NSURLSessionDownloadDelegate 和 NSURLSessionDelegate 方法会因为// 没有 对 session 的 delegate 设定而不会被调用。参见上面的 backgroundURLSession NSURLSession *backgroundSession = [self backgroundURLSession]; NSLog(@"Rejoining session with identifier %@ %@", identifier, backgroundSession); // 保存 completion handler 以在处理 session 事件后更新 UI [self addCompletionHandler:completionHandler forSession:identifier]; } - (void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session { NSLog(@"Background URL session %@ finished events. ", session); if (session.configuration.identifier) { // 调用在 -application:handleEventsForBackgroundURLSession: 中保存的 handler [self callCompletionHandlerForSession:session.configuration.identifier]; } } - (void)addCompletionHandler:(CompletionHandlerType)handler forSession:(NSString *)identifier { if ([self.completionHandlerDictionary objectForKey:identifier]) { NSLog(@"Error: Got multiple handlers for a single session identifier. This should not happen. "); } [self.completionHandlerDictionary setObject:handler forKey:identifier]; } - (void)callCompletionHandlerForSession: (NSString *)identifier { CompletionHandlerType handler = [self.completionHandlerDictionary objectForKey: identifier]; if (handler) { [self.completionHandlerDictionary removeObjectForKey: identifier]; NSLog(@"Calling completion handler for session %@", identifier); handler(); } }

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