iOS 7 核心位置 : region monitoring fails on the first time after location services are authorised

Question

我使用 CoreLocation 在我的应用程序上发现了一个奇怪的行为。我正在使用区域监控功能，但在授权位置服务(通过弹出窗口或设置 -> 位置服务)后，区域监控失败(操作无法完成。kCLErrorDomain 错误 5.)。如果我关闭应用程序并重新启动(因此已经获得授权)，一切都会按预期进行。我的代码如下所示:

-(void)initializeLocationServices
{
    NSLog(@"Started location services");

    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate = self;
    locationManager.distanceFilter = kCLDistanceFilterNone;
    locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation;
    locationManager.pausesLocationUpdatesAutomatically = NO;

    [locationManager startUpdatingLocation]; // to show authorisation popup
}

-(CLCircularRegion*)createRegion
{   
    // Test coordinates
    CLLocationDegrees latitude = 50;
    CLLocationDegrees longitude = -1;
    CLLocationDistance radius = 50; // meters;

    // If radius is too large, registration fails automatically, so limit the radius to the maximum value
    if (radius > locationManager.maximumRegionMonitoringDistance) {
        radius = locationManager.maximumRegionMonitoringDistance;
    }

    CLCircularRegion* region = [[CLCircularRegion alloc] initWithCenter:CLLocationCoordinate2DMake(latitude, longitude) radius:radius identifier:@"TEST"];

    region.notifyOnEntry = YES;
    region.notifyOnExit = YES;

    NSLog(@"Created region");

    return region;
}

-(void)monitorProximity
{
    CLRegion *region = [self createRegion];

    // Check if support is unavailable
    if ( ![CLLocationManager isMonitoringAvailableForClass:[CLRegion class]]) {
        NSLog( @"Failed to initialise region monitoring: support unavailable");
        return;
    }

    // Check if authorised
    if ([CLLocationManager authorizationStatus] != kCLAuthorizationStatusAuthorized) {
        NSLog( @"Failed to initialise region monitoring: app not authorized to use location services");
        return;
    } else {
        NSLog(@"Started monitoring proximity");
    }


    // Clear out any old regions to prevent buildup.
    if ([locationManager.monitoredRegions count] > 0) {
        for (id obj in locationManager.monitoredRegions)
            [locationManager stopMonitoringForRegion:obj];
    }

    [locationManager startMonitoringForRegion:region];
}

-(void)locationManager:(CLLocationManager *)manager didStartMonitoringForRegion:(CLRegion *)region
{
    NSLog(@"Started monitoring for region: %@", [region description]);
    [locationManager requestStateForRegion:region]; // check if already inside region
}

-(void)locationManager:(CLLocationManager *)manager monitoringDidFailForRegion:(CLRegion *)region withError:(NSError *)error
{
    NSLog(@"Failed to start monitoring for region: %@", [error localizedDescription]);
}


-(void)locationManager:(CLLocationManager *)manager didDetermineState:(CLRegionState)state forRegion:(CLRegion *)region
{
    NSLog(@"didDetermineState");

    if (state == CLRegionStateInside) {

        NSLog(@"inside");
        return;


    } else if (state == CLRegionStateOutside) {
        NSLog(@"outside");

    } else {
        NSLog(@"unknown");
    }

}

-(void)locationManager:(CLLocationManager *)manager didEnterRegion:(CLRegion *)region
{
    NSLog(@"didEnterRegion");
}

-(void)locationManager:(CLLocationManager *)manager didExitRegion:(CLRegion *)region
{
    NSLog(@"didExitRegion");
}

-(void)locationManager:(CLLocationManager *)manager didChangeAuthorizationStatus:(CLAuthorizationStatus)status
{
    NSLog(@"Monitoring authorisation status is now: %@", status == kCLAuthorizationStatusAuthorized ? @"authorized" : @"not authorized");

    if (status == kCLAuthorizationStatusAuthorized) {
        [self monitorProximity];
    }
}

我是不是做错了什么？调用 didChangeAuthorizationStatus 后流程是否有问题？

Answer 1

来自 other user reports ，似乎 kCLErrorDomain 5 是区域监控失败的“包罗万象”；它没有提供太多有用的信息。我相信您的问题是由线路引起的

[locationManager requestStateForRegion:region]; // check if already inside region

您从委托(delegate)方法 didStartMonitoringForRegion: 中调用它

我在自己的项目中看到了一些非常相似的东西，把这条线去掉(或延迟执行一段时间)解决了这个问题。我最好的猜测是，当此委托(delegate)方法触发时，iOS 仍在运行一些内部区域监视代码，因此现在不是调用 requestStateForRegion:

的合适时间

试着把这个拿出来，看看是不是答案。