CLLocationManager и вопросы точности - любой опыт?

Ответ 1

Я не помню, какой проект был именно таким, из которого я получил следующий код, но это сработало для меня очень хорошо (я помню, это было из видео WWDC 2010). В моем коде я оставил комментарии от оригинального проекта тактично, поэтому, надеюсь, это поможет.

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    // test the age of the location measurement to determine if the measurement is cached
    // in most cases you will not want to rely on cached measurements
    NSTimeInterval locationAge = -[newLocation.timestamp timeIntervalSinceNow];

    if (locationAge > 5.0) return;

    // test that the horizontal accuracy does not indicate an invalid measurement
    if (newLocation.horizontalAccuracy < 0) return;

    // test the measurement to see if it is more accurate than the previous measurement
    if (bestEffortAtLocation == nil || bestEffortAtLocation.horizontalAccuracy > newLocation.horizontalAccuracy) {
        // store the location as the "best effort"
        self.bestEffortAtLocation = newLocation;

        // test the measurement to see if it meets the desired accuracy
        //
        // IMPORTANT!!! kCLLocationAccuracyBest should not be used for comparison with location coordinate or altitidue 
        // accuracy because it is a negative value. Instead, compare against some predetermined "real" measure of 
        // acceptable accuracy, or depend on the timeout to stop updating. This sample depends on the timeout.
        //
        if (newLocation.horizontalAccuracy <= locationManager.desiredAccuracy) {
            // we have a measurement that meets our requirements, so we can stop updating the location
            // 
            // IMPORTANT!!! Minimize power usage by stopping the location manager as soon as possible.
            //
            [self stopUpdatingLocation:NSLocalizedString(@"Acquired Location", @"Acquired Location")];

            // we can also cancel our previous performSelector:withObject:afterDelay: - it no longer necessary
            [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(stopUpdatingLocation:) object:nil];
        }
    }
}

Надеюсь, это поможет!

Через GetLocationViewController.m в примере проекта Apple Locate Me, доступного по адресу:

https://developer.apple.com/library/content/samplecode/LocateMe/Introduction/Intro.html

Ответ 2

Из ответа donkim рассмотрим замену этой строки

[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(stopUpdatingLocation:) object:nil];

с линией

[NSObject cancelPreviousPerformRequestsWithTarget: self];