Iphone UIlocalNotification现在没有启动后台任务就出现了

我有一个voip应用程序

我在我的应用程序中使用

UILocalNotification

，在应用程序处于后台时，为传入呼叫发出警报通知

当应用程序在后台时，在收到传入呼叫后，调用以下函数

-(void)showLocalNotification:(NSNotification *)notification {

    NSDictionary *dic = notification.userInfo;
    NSString *msg = [dic objectForKey:@"msg"];
    NSString *sound = [dic objectForKey:@"sound"];

    [[UIApplication sharedApplication] cancelAllLocalNotifications];
    UILocalNotification *_localNotification = [[UILocalNotification alloc]init];

    //setting the fire dat of the local notification
    _localNotification.fireDate = [NSDate dateWithTimeIntervalSinceNow:1];

    //setting the time zone
    _localNotification.timeZone = [NSTimeZone defaultTimeZone];

    //setting the message to display
    _localNotification.alertBody = msg;

    //default notification sound
    if ([sound length]==0) {
        _localNotification.soundName = UILocalNotificationDefaultSoundName; 
    } else {
        _localNotification.alertAction = NSLocalizedString(@"Receive", nil);
        _localNotification.soundName = @"myringtone.aif";
    }
    //displaying the badge number
    _localNotification.applicationIconBadgeNumber = [[UIApplication sharedApplication]applicationIconBadgeNumber]+1;

    //schedule a notification at its specified time with the help of the app delegate
    [[UIApplication sharedApplication]scheduleLocalNotification:_localNotification];

}

此功能设置scheduleLocal通知，以显示带有两个按钮的警报

Cancel

和

Receive

，这两个按钮在一秒钟后触发

现在的问题是：

仅当后台任务按以下方式启动时，此本地通知才会显示给用户

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    UIApplication* app = [UIApplication sharedApplication];
    bgTask = [app beginBackgroundTaskWithExpirationHandler:^{        
        [app endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];
}

但10分钟后，后台任务停止。然后，虽然本地通知触发，但用户不会看到它（触发后会打印日志）

我确实修改了

applicationidenterbackground

函数，如下所示，以重新启动后台任务以进行长时间运行。但是不能

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    expirationHandler = ^{
        [app endBackgroundTask:self.bgTask];
        self.bgTask = UIBackgroundTaskInvalid;
        self.bgTask = [app beginBackgroundTaskWithExpirationHandler:expirationHandler];
    }
   self.bgTask = [app beginBackgroundTaskWithExpirationHandler:expirationHandler];
}

现在的问题是：

当应用程序处于后台时，是否有任何方式可以触发本地通知并显示给用户

若后台任务是强制性的，那个么在10分钟后显示本地通知以显示给用户怎么可能是长期运行的呢

我正在使用

iphone3gs

、

iphone4

和

iphone5

试试这个：

- (void)applicationDidEnterBackground:(UIApplication *)application
{

    __block UIBackgroundTaskIdentifier bgTask ;
    UIApplication  *app = [UIApplication sharedApplication];
    bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
        [app endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];
    pollingTimer2 = [NSTimer scheduledTimerWithTimeInterval:4.0f target:self  selector:@selector(process)  userInfo:nil repeats:YES];
}
-(void) process
{
   [self didLocalNotification];

}

-(void)didLocalNotification
{

    [[UIApplication sharedApplication]cancelAllLocalNotifications];
    UILocalNotification *localNotification = [[UILocalNotification alloc] init];
    if (localNotification == nil)
    {
        return;
    }

    NSLog(@"calling didLocalNotification");
    localNotification.applicationIconBadgeNumber =0;
    localNotification.alertBody =@"Message!";
    localNotification.soundName = UILocalNotificationDefaultSoundName;
    localNotification.fireDate = [NSDate dateWithTimeIntervalSinceNow:0];
    localNotification.timeZone = [NSTimeZone defaultTimeZone];
    [[UIApplication sharedApplication] scheduleLocalNotification:localNotification];
}