didUpdateToLocation
回調可能由於許多原因而更新,處理這個問題的好策略是逐步過濾基於時間戳的結果,然後要求準確性。
蘋果提供的LocateMe sample app一個很好的例子:
- (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 (self.bestEffortAtLocation == nil || self.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")];
}
}
}
太好了,謝謝! – user1553961
謝謝,但如果我想讓位置服務保持打開狀態呢? stopUpdating可能會阻止位置管理器不行? – Dejell
此代碼允許位置管理器根據需要進行更新以確定用戶所需的準確度。在哪一點上,電源管理停止更新是合乎情理的。如果您的應用程序需要在用戶更改位置時監視用戶,那麼您可以註冊重要更改:'[locationManager startMonitoringSignificantLocationChanges];'請參閱[docs](https://developer.apple.com/library/ios/documentation/ userexperience /概念性/ LocationAwarenessPG/CoreLocation/CoreLocation.html) – cleverbit