iOS：更新后核心位置关闭？

Question

显然，为了节省电量，我们需要尽快使用 CoreLocation，并在不需要时将其关闭。我有一个跟踪用户位置的 GPS 应用程序，因此我使用几乎所有好的位置更新。我是否仍然需要以某种时间间隔关闭核心位置？

在苹果的“LocateMe”应用程序中，他们似乎在找到位置时将其关闭，但这让我感到困惑，它什么时候会重新打开？就我而言，暂时关闭然后再打开似乎没有意义。

想法？

来自“定位我”：

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    // store all of the measurements, just so we can see what kind of data we might receive
    [locationMeasurements addObject:newLocation];
    // 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's no longer necessary
            [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(stopUpdatingLocation:) object:nil];
        }
    }
    // update the display with the new location data
    [self.tableView reloadData];    
}

Answer 1

在我看来，您想要每米左右更新位置与想要节省电池并因此想要尽快使用 CoreLocation 然后将其关闭“不需要时” 的双重要求是互不相容。如果您需要每米左右更新一次位置，那么当您不需要打开位置服务时，应用程序将永远不会处于前台。根据应用程序的性质，您可能希望在进入后台或屏幕锁定时关闭位置服务...

另一种例外可能是，如果用户静止了一会儿。 Apple 提供 位置服务发生重大变化，但这似乎不适合您的需求，如果您想要逐米更新......它只是没有那个级别的分辨率。

那么可能没有一个解决方案能够同时满足您的愿望吗？

Answer 2

这取决于您需要定位的频率。如果您在应用程序运行时始终需要它，最好在 applicationWillBecomeActive 中打开位置更新并在 applicationWillResignActive 中关闭更新

Answer 3

您可以配置精度和距离过滤器，

locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
locationManager.distanceFilter = 10;

这取决于您需要的精度和更新频率