那些遇到过的问题

应用在后台时启动CLLocationManager位置更新

vil*_*ovi 11 gps location background core-location ios

我正在构建一个使用CoreLocation的应用程序有两个目的:

  1. 首先,监控信标区域.大多数情况下,我们使用充当信标的特定硬件设备,并使用CoreLocation跟踪该信标连接的状态.

  2. 其次,当应用程序检测到与信标设备断开连接时,我们希望启动GPS进程以找到断开连接的位置.

在大多数情况下,当应用程序处于后台时,会发生信标设备的断开连接回调.因此,应用程序必须通过-startUpdatingLocation在后台进行呼叫来启动GPS跟踪.

这就是问题所在.如果-startUpdatingLocation在应用程序处于后台时调用发生,iOS似乎无法启用位置后台更新.

显然,我已经正确配置了背景模式,NSLocationAlwaysUsageDescription将属性设置_locationManager.allowsBackgroundLocationUpdates为YES.

令人惊奇的事情:如果我-startUpdatingLocation在前台呼叫然后切换到后台,位置更新会在后台正确发送.但是,当-startUpdatingLocation在后台进行调用时,应用程序会收到2或3个位置更新,然后永久暂停..直到我手动将应用程序恢复到前台,当位置更新恢复时,即使我将应用程序切换到再次背景.

有人知道或理解我该怎么做才能解决这个问题？或者它是iOS的主要约束？由于我的应用程序的要求,我真的需要在应用程序处于后台时开始定位更新(在信标的回调内部确实退出区域).

顺便说一句,如果你想重现这个问题很容易.只需在Xcode中创建一个空白项目,然后将此代码添加到默认视图控制器中.请记住启用后台模式为info.plist键"NSLocationAlwaysUsageDescription"添加说明.

- (void)viewDidLoad 
{
    [super viewDidLoad];

    _locationManager = [[CLLocationManager alloc] init];

    if (NSFoundationVersionNumber > NSFoundationVersionNumber_iOS_8_3)
        _locationManager.allowsBackgroundLocationUpdates = YES;

    _locationManager.delegate = self;
    _locationManager.activityType = CLActivityTypeOther;
    _locationManager.desiredAccuracy = kCLLocationAccuracyBest;
    _locationManager.distanceFilter = kCLDistanceFilterNone;

    [_locationManager requestAlwaysAuthorization];

    // Creating a background task to delay the start of the startUpdatingLocation
    __block UIBackgroundTaskIdentifier taskIdentifier = UIBackgroundTaskInvalid;
    taskIdentifier = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        [[UIApplication sharedApplication] endBackgroundTask:taskIdentifier];
    }];

    // Delaying the call to startUpdatingLocation 10 seconds, enough time to dismiss the application
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(10 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [_locationManager startUpdatingLocation];
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [[UIApplication sharedApplication] endBackgroundTask:taskIdentifier];
        });
    });
}
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然后,通过执行一些NSLog来跟踪CLLocationManager委托,看看会发生什么.

谢谢,

小智 2

距离您提出这个问题已经过去 3 个月了。你自己已经想出来了吗？

我尝试了你的代码。我将一些放在委托函数NSLogs中AppDelegate，并在viewDidLoad. 另外，在AppDelegate课堂上，我注销了后台剩余时间。

如果startUpdatingLocation在进入后台之前调用：

2016-08-18 01:22:52.355 test background GPS from StackOF[2267:745042] viewDidLoad
2016-08-18 01:22:52.376 test background GPS from StackOF[2267:745042] _locationManager.allowsBackgroundLocationUpdates = YES;
2016-08-18 01:22:52.382 test background GPS from StackOF[2267:745042] _locationManager requestAlwaysAuthorization
2016-08-18 01:22:52.410 test background GPS from StackOF[2267:745042] applicationDidBecomeActive
2016-08-18 01:22:52.469 test background GPS from StackOF[2267:745042] viewDidAppear
2016-08-18 01:23:03.361 test background GPS from StackOF[2267:745042] [_locationManager startUpdatingLocation];
2016-08-18 01:23:03.362 test background GPS from StackOF[2267:745042] start updating location, _locationManager.allowsBackgroundLocationUpdates == YES
2016-08-18 01:23:03.382 test background GPS from StackOF[2267:745042] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 65.000000
2016-08-18 01:23:03.630 test background GPS from StackOF[2267:745042] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 1743.000000
2016-08-18 01:23:03.709 test background GPS from StackOF[2267:745042] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 1743.000000
2016-08-18 01:23:03.716 test background GPS from StackOF[2267:745042] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 1743.000000
2016-08-18 01:23:03.720 test background GPS from StackOF[2267:745042] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 1743.000000
2016-08-18 01:23:03.814 test background GPS from StackOF[2267:745042] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 65.000000
2016-08-18 01:23:05.004 test background GPS from StackOF[2267:745042] inner block [[UIApplication sharedApplication] endBackgroundTask:taskIdentifier];
2016-08-18 01:23:05.005 test background GPS from StackOF[2267:745042] inner block start updating location, _locationManager.allowsBackgroundLocationUpdates == YES
2016-08-18 01:23:08.287 test background GPS from StackOF[2267:745042] applicationDidEnterBackground. Background time left: 179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368.000000
2016-08-18 01:23:10.319 test background GPS from StackOF[2267:745042] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 65.000000
2016-08-18 01:23:19.321 test background GPS from StackOF[2267:745042] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 65.000000
/****
Keep on polling...
****/
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如果startUpdatingLocation进入后台后调用：

2016-08-18 01:34:29.023 test background GPS from StackOF[2285:747132] viewDidLoad
2016-08-18 01:34:29.030 test background GPS from StackOF[2285:747132] _locationManager.allowsBackgroundLocationUpdates = YES;
2016-08-18 01:34:29.033 test background GPS from StackOF[2285:747132] _locationManager requestAlwaysAuthorization
2016-08-18 01:34:29.047 test background GPS from StackOF[2285:747132] applicationDidBecomeActive
2016-08-18 01:34:29.104 test background GPS from StackOF[2285:747132] viewDidAppear
2016-08-18 01:34:31.612 test background GPS from StackOF[2285:747132] applicationDidEnterBackground. Background time left: 179.964144
2016-08-18 01:34:40.004 test background GPS from StackOF[2285:747132] [_locationManager startUpdatingLocation];
2016-08-18 01:34:40.006 test background GPS from StackOF[2285:747132] start updating location, _locationManager.allowsBackgroundLocationUpdates == YES
2016-08-18 01:34:40.290 test background GPS from StackOF[2285:747132] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 10.000000
2016-08-18 01:34:40.332 test background GPS from StackOF[2285:747132] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 355.117789
2016-08-18 01:34:40.336 test background GPS from StackOF[2285:747132] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 355.118536
2016-08-18 01:34:40.493 test background GPS from StackOF[2285:747132] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 355.141209
2016-08-18 01:34:40.496 test background GPS from StackOF[2285:747132] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 355.147748
2016-08-18 01:34:40.505 test background GPS from StackOF[2285:747132] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 355.148158
2016-08-18 01:34:40.507 test background GPS from StackOF[2285:747132] Lat/Long: <redacted GPS coordinates>, horizontal accuracy: 65.000000
2016-08-18 01:34:41.640 test background GPS from StackOF[2285:747132] inner block [[UIApplication sharedApplication] endBackgroundTask:taskIdentifier];
2016-08-18 01:34:41.642 test background GPS from StackOF[2285:747132] inner block start updating location, _locationManager.allowsBackgroundLocationUpdates == YES
/****
stops polling...
****/
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记下剩余的后台时间。如果应用程序在 CLLocationManager 开始更新位置之前进入后台，则剩余的后台时间为 3 分钟。我自己也不太确定，因为我也有自己的 GPS 后台运行问题，但从这个简短的测试来看，CLLocationManager 似乎必须在应用程序进入后台之前被调用。

这是我放置 NSLog 的位置：

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    NSLog(@"viewDidLoad");

    _locationManager = [[CLLocationManager alloc] init];

    if (NSFoundationVersionNumber > NSFoundationVersionNumber_iOS_8_3)
    {
        _locationManager.allowsBackgroundLocationUpdates = YES;
        NSLog(@"_locationManager.allowsBackgroundLocationUpdates = YES;");
    }



    _locationManager.delegate = self;
    _locationManager.activityType = CLActivityTypeOther;
    _locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation;
    _locationManager.distanceFilter = kCLDistanceFilterNone;

    [_locationManager requestAlwaysAuthorization];
    NSLog(@"_locationManager requestAlwaysAuthorization");

    // Creating a background task to delay the start of the startUpdatingLocation
    __block UIBackgroundTaskIdentifier taskIdentifier = UIBackgroundTaskInvalid;
    taskIdentifier = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        [[UIApplication sharedApplication] endBackgroundTask:taskIdentifier];
        NSLog(@"[[UIApplication sharedApplication] endBackgroundTask:taskIdentifier];");
    }];

    // Delaying the call to startUpdatingLocation 10 seconds, enough time to dismiss the application
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(10 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [_locationManager startUpdatingLocation];
        NSLog(@"[_locationManager startUpdatingLocation];");
        if(_locationManager.allowsBackgroundLocationUpdates == YES)
        {
            NSLog(@"start updating location, _locationManager.allowsBackgroundLocationUpdates == YES");
        }
        else
        {
            NSLog(@"start updating location, _locationManager.allowsBackgroundLocationUpdates == NO");
        }
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [[UIApplication sharedApplication] endBackgroundTask:taskIdentifier];
            NSLog(@"inner block [[UIApplication sharedApplication] endBackgroundTask:taskIdentifier];");
            if(_locationManager.allowsBackgroundLocationUpdates == YES)
            {
                NSLog(@"inner block start updating location, _locationManager.allowsBackgroundLocationUpdates == YES");
            }
            else
            {
                NSLog(@"inner block start updating location, _locationManager.allowsBackgroundLocationUpdates == NO");
            }

        });
    });

}
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委托CLLocationManager函数：

-(void)locationManager:(CLLocationManager *) manager didUpdateLocations:(nonnull NSArray<CLLocation *> *)locations
{
    CLLocation *location = [locations firstObject];
    NSLog(@"Lat/Long: %f %f, horizontal accuracy: %f",
          location.coordinate.latitude,
          location.coordinate.longitude,
          location.horizontalAccuracy);
}
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应用程序委托：

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

    NSLog(@"applicationDidEnterBackground. Background time left: %f", [[UIApplication sharedApplication] backgroundTimeRemaining]);

}
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TL;DR：尝试startUpdatingLocation直接在AppDelegate 中viewDidLoad或在 AppDelegate 中调用application:didFinishLaunchingWithOptions:

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