使用核心数据绕过 CLRegion 20 区域上限的位置警报

Question

我有一个应用程序可以在核心数据中存储兴趣点 (POI) managedObjectContext。如果 currentLocation 在 managedObjectContext 中指定的 POI 范围内，我的 objective 会发出警报。在阅读 CLRegion 时，似乎可以监控的区域数量上限为 20。

为了避开区域监控上限，我的游戏计划是在每次我的位置管理器的 didUpdateLocations 触发时浏览我的 managedObjectContext 以获得 latitude/longitude 坐标并计算 POI 之间的距离应用程序：

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
    CLLocation *location = [locations lastObject];
    NSLog(@"LocationManager Latitude %+.6f, Longitude %+.6f\n",
          location.coordinate.latitude,
          location.coordinate.longitude);
    // TODO: compute distances between objects in managedObjectContext
    [self calculateDistances];
    self.currentLocation = location;
}

// method to compute distances
- (void) calculateDistances {

    // for POI in managedObjectContext, do the following
    CLLocation *locA = [[CLLocation alloc] initWithLatitude:self.currentLocation.coordinate.latitude longitude:self.currentLocation.coordinate.longitude];

    CLLocation *locB = [[CLLocation alloc] initWithLatitude:POIlatitude longitude:POIlongitude];

    CLLocationDistance distance = [locA distanceFromLocation:locB];

    if (distance < 1000) {
        // popup alert
    }

}

我只使用 managedObjectContext 来显示数据。在这种情况下，我没有显示任何东西——相反，当 didUpdateLocations 触发时，我只是运行通过我的 MOC 中的对象，提取坐标并计算距离。有什么想法可以实现吗？

Answer 1

我打电话给我的 class LocationManager，它是一个单身人士 class。在header中，我为NSManagedObjectContext添加了一个属性。

.h

@property (nonatomic, weak) NSManagedObjectContext *managedObjectContext;

我的核心数据堆栈在我的 AppDelegate 中，所以我将 LocationManager 实现的 init 方法调整为 "see" 它：

.m

- (id)init {
    self = [super init];
    if (!self.locationManager) {
        // This is so I can get a reference to the managedObjectContext
        AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
        self.managedObjectContext = appDelegate.managedObjectContext;

        self.locationManager = [[CLLocationManager alloc]init];

        if ([self.locationManager respondsToSelector:@selector(requestAlwaysAuthorization)]) {
            [self.locationManager requestAlwaysAuthorization];
        }

        self.locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
        self.locationManager.distanceFilter = 100; // meters
        self.locationManager.delegate = self;
    }
    return self;
}

更进一步，当 didUpdateLocations 方法触发时，我添加了对 [self calculateDistances] 的调用，如下所示：

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
    CLLocation *location = [locations lastObject];
    NSLog(@"LocationManager Latitude %+.6f, Longitude %+.6f\n",
          location.coordinate.latitude,
          location.coordinate.longitude);
    [self calculateDistances];
    self.currentLocation = location;
}

// method to compute distances
- (void) calculateDistances {

    NSError *error;
    NSFetchRequest *coordinateRetrieval = [[NSFetchRequest alloc]initWithEntityName:@"PointOfInterest"];
    NSArray *pois = [self.managedObjectContext executeFetchRequest:coordinateRetrieval error:&error];

    for (PointOfInterest *venue in poi) {
        CLLocation *locA = self.currentLocation;
        CLLocation *locB = [[CLLocation alloc]initWithLatitude:[venue.latitude doubleValue] longitude:[venue.longitude doubleValue]];
        CLLocationDistance distance = [locA distanceFromLocation:locB];

        if (distance < 1000) {
            // popup alert
        }
        NSLog(@"The distance from currentLocation to venue is %lf meters", distance);
    }
}

使用核心数据绕过 CLRegion 20 区域上限的位置警报

Location alerts using Core Data to get around CLRegion 20 region cap

core-data

cllocationmanager

geofencing

ios8