IOS 后台之长时间任务 beginBackgroundTaskWithExpirationHandler 申请后台十分钟 600秒
10分钟
beginBackgroundTaskWithExpirationHandler，beginBackgroundTaskWithName
endBackgroundTask
定义变量
UIBackgroundTaskIdentifier bgTask;
- (void)applicationDidEnterBackground:(UIApplication *)application { bgTask = [application beginBackgroundTaskWithName:@"MyTask" expirationHandler:^{ // Clean up any unfinished task business by marking where you // stopped or ending the task outright. [application endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }]; // Start the long-running task and return immediately. dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // Do the work associated with the task, preferably in chunks. [application endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }); }
Declaration
Swift
func beginBackgroundTaskWithExpirationHandler(_ handler: (() -> Void)?) -> UIBackgroundTaskIdentifier
Objective-C
- (handler
Listing 4-2 Starting a background task at quit time - (void)applicationDidEnterBackground:(UIApplication *)application { UIApplication* app = [UIApplication sharedApplication]; bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ [app endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }]; // Start the long-running task and return immediately. dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // Do the work associated with the task. [app endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }); }
^{} block 语法。
dispatch_queue_create
dispatch_release
dispatch_async_f
Queue: dispatch_queue_t; Queue := dispatch_queue_create('Video Capture Queue', 0);