3.这里有一个问题，就是客户端是通过心跳来和服务端保持连接，心跳是由定时器触发的，当我退到后台以后，定时器方法被挂起，那么通过如下设置来在后台运行定时器

beginBackgroundTaskWithExpirationHandler

-(void)applicationDidEnterBackground:(UIApplication*)application{UIApplication*app = [UIApplication sharedApplication];__blockUIBackgroundTaskIdentifier bgTask;bgTask= [app beginBackgroundTaskWithExpirationHandler:^{dispatch_async(dispatch_get_main_queue(),^{if(bgTask != UIBackgroundTaskInvalid){bgTask= UIBackgroundTaskInvalid;}});}];dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0),^{dispatch_async(dispatch_get_main_queue(),^{if(bgTask != UIBackgroundTaskInvalid){bgTask= UIBackgroundTaskInvalid;}});});}

 

2

- (void)applicationDidEnterBackground:(UIApplication *)application{    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.     // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.        testPeripheral = [[ViewController sharedInst] userGetCurrentPeri];        NSLog(@"Saving all fobs... testPeripheral:%@", testPeripheral);        /// _scanTimer=nil;        //    NSError *error;    //    if (![self.managedObjectContext save:&error])    //    {    //        NSLog(@"Saving failed: %@", error);    //    }    //entryBackgroundMode是定时器呼叫的函数//    if (!_scanTimer /* &&[USER_DEFAULT boolForKey:KEY_BACKGROUND_OPEN]*/) {//        NSLog(@"_scanTimer active ...");//        _scanTimer = [NSTimer timerWithTimeInterval:1.0f target:self selector:@selector(entryBackgroundMode) userInfo:nil repeats:YES];//        //        [[NSRunLoop currentRunLoop] addTimer:_scanTimer forMode:NSDefaultRunLoopMode /* NSRunLoopCommonModes */];//    }    /// CLLocationManager * manager = [CLLocationManager new];        __block UIBackgroundTaskIdentifier background_task;        background_task = [application beginBackgroundTaskWithExpirationHandler:^ {        [application endBackgroundTask: background_task];        background_task = UIBackgroundTaskInvalid;    }];        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{        while(TRUE)        {            [NSThread sleepForTimeInterval:1];                        //编写执行任务代码            [self entryBackgroundMode]; //entryBackgroundModeReadRSSI是定时器呼叫的函数//            _scanTimer = [NSTimer timerWithTimeInterval:0.10f target:self selector:@selector(entryBackgroundModeReadRSSI) userInfo:nil repeats:NO];//            [[NSRunLoop currentRunLoop] addTimer:_scanTimer forMode:NSDefaultRunLoopMode /* NSRunLoopCommonModes */];        }                [application endBackgroundTask: background_task];        background_task = UIBackgroundTaskInvalid;    });}

 

//注入定时器     NSError *setCategoryErr = nil;     NSError *activationErr  = nil;     [[AVAudioSession sharedInstance]      setCategory: AVAudioSessionCategoryPlayback      error: &setCategoryErr];     [[AVAudioSession sharedInstance]      setActive: YES      error: &activationErr];      - (void)applicationDidEnterBackground:(UIApplication *)application      {          //后台继续运行定时器          UIApplication*   app = [UIApplication sharedApplication];          __block    UIBackgroundTaskIdentifier bgTask;          bgTask = [app beginBackgroundTaskWithExpirationHandler:^{              dispatch_async(dispatch_get_main_queue(), ^{                  if (bgTask != UIBackgroundTaskInvalid)                  {                      bgTask = UIBackgroundTaskInvalid;                  }              });          }];                    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{              dispatch_async(dispatch_get_main_queue(), ^{                  if (bgTask != UIBackgroundTaskInvalid)                  {                      bgTask = UIBackgroundTaskInvalid;                  }              });          });      }