So, my app requires to capture location every 15 meter.
in viewDidLoad
NSOperationQueue.mainQueue().addOperationWithBlock {
self.manager = CLLocationManager()
self.manager.delegate = self
self.manager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters
self.manager.distanceFilter = 15.0
self.manager.headingFilter = 10
self.manager.startUpdatingLocation()
}
First time (i don't move), in
func locationManager(manager:CLLocationManager, didUpdateLocations locations:[AnyObject])
i get (real example):
*.1488241293991
*.5997807433053
second time:
*.1489010891664
*.599624152471
I test on real device with ios7, and swift.
What am I doing wrong?
Thanks!
From CLLocationManager Class Reference:
When requesting high-accuracy location data, the initial event delivered by the location service may not have the accuracy you requested. The location service delivers the initial event as quickly as possible. It then continues to determine the location with the accuracy you requested and delivers additional events, as necessary, when that data is available.
So the first location you retrieve might be inaccurate.
Related
I have two constraints in my app, one is user location and the other one is time. Following is the simple location implementation.
func determineMyCurrentLocation() {
locationManager = CLLocationManager()
locationManager.delegate = self
locationManager.allowsBackgroundLocationUpdates = true
locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters
locationManager.requestAlwaysAuthorization()
locationManager.distanceFilter = 20
if CLLocationManager.locationServicesEnabled() {
locationManager.startUpdatingLocation()
}
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
print("*******Location updated*******")
}
With this code, I expect to get triggered every time the user location changes by 20m (in background as well). However, I also need to track the time the user stays in a particular location. Since i need to track the background case, I cannot use timer.
I followed https://www.raywenderlich.com/143128/background-modes-tutorial-getting-started to try background task but as stated in the article, the background time allowed that I got was around 3 min (which is variable). So i believe I cannot go with this.
How can I solve this?
EDIT: I also need to make an api call if the user stays in a location for X minutes. So for that case, it would not be feasible to wait for location updates and calculate the time differences. I could previously solve this by removing the distance filter and continuously checking the location and comparing the time and location. I guess continuous location tracking will get the app rejected, that's why I went for filter. But i am not sure if it will still get rejected or not since iOS will need to track the location for filter as well.
You can use simple Date objects to track the time spent between location updates even if your app is in the background. Simply declare a Date property for your class, update its value from func locationManager(_:, didUpdateLocations:) and compare that to the current time.
// Declare this in a scope that can be accessed from `didUpdateLocations` and where its value won't be released from memory
var lastUpdateTimestamp = Date()
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
let now = Date()
let timeSinceLastUpdate = now.timeIntervalSince(lastUpdateTimestamp)
print("\(timeSinceLastUpdate) seconds passed since last location update")
lastUpdateTimestamp = now
}
Response to the question edit: making an API call after X minutes have passed in the background without a location update is not possible, since there's no supported background mode for executing arbitrary functions at specific points in time. Getting rid of the distance filter as you explained in your edit could be a valid alternative, however if your app is only using location updates to be able to make the API calls and isn't actually doing anything with those locations, your app might indeed get rejected.
When you receive a new location update, check the time difference from the previous update.. giving you the time that they were at the last location.
Depending on what you are doing with these location updates, this might just be pulling the latest update from some DB, or posting to an API.
An example..
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
print("*******Location updated*******")
let lastUpdateDate = // get the last datetime you received information
let currentDate = Date()
let minutesDifference = let componentsLeftTime = Calendar.current.dateComponents([.minute], from: lastUpdateDate, to: currentDate)
}
Please check the code:
let manager = CLLocationManager()
//Location manager to determine the current location
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
let location = locations[0]
lat = location.coordinate.latitude
lon = location.coordinate.longitude
let currentLocation = CLLocation(latitude: lat!, longitude: lon!)
}
And i have few more functions in viewDidLoad():
override func viewDidLoad() {
super.viewDidLoad()
manager.delegate = self
manager.desiredAccuracy = kCLLocationAccuracyBest
manager.requestWhenInUseAuthorization()
//Here i want to get the result immediately, but...
manager.startUpdatingLocation()
parseJSONfunction()
anotherFunction()
anotherFunction2()
...}
So, i can't get the result of manager.startUpdatingLocation() function until all viewDidLoad() stuff loads.
The question: Is it possible to get coordinates before all other functions runs? If yes, please describe how?
The question: Is it possible to get coordinates before all other functions runs?
In a word, no. The location manager is asynchronous. You ask it to start updating your location and it fires up the GPS and tries to get a fix (it also uses cell towers, WiFi base stations, etc.) It can take several seconds (or longer) in order to get a reasonably accurate reading.
When I'm writing location-aware apps, I usually start the location manager, and in my locationManager(_:didUpdateLocations:) method I check the horizontal accuracy of the result and only take it if it's at least reasonably accurate. This can make it take even longer.
If you load a viewController it's synchronous. The system does the setup, which causes various framework calls to fire, and then viewDidLoad gets called, synchronously once the view loads. If you start the location manager when the user asks to display a new view controller, you can't possibly have a location fix by the time viewDidLoad is called.
If you load your app, have the app delegate invoke a singleton to begin location updates, and then wait for the user to switch to your other screen, where you then ask the singleton for the location during viewDidLoad you have a good chance of getting a good location reading, but even then it isn't certain.
I'm using CLLocationManager to get users location.
I want to get a single location update.
My problem is that I'm getting really bad horizontalAccuracy
location is %# <+xx.xxxxxx,+yy.yyyyyyy> +/- 3881.91m
verticalAccuracy: 65.4401861912846, horizontalAccuracy: 3881.90892434957
Code:
fileprivate lazy var locationManager: CLLocationManager = {
let manager = CLLocationManager()
manager.desiredAccuracy = kCLLocationAccuracyBest
manager.delegate = self
manager.requestAlwaysAuthorization()
manager.pausesLocationUpdatesAutomatically = false
manager.desiredAccuracy = kCLLocationAccuracyBest
manager.distanceFilter = kCLDistanceFilterNone
return manager
}()
override init() {
super.init()
locationManager.startUpdatingLocation()
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
guard let mostRecentLocation = locations.last else {
return
}
let verticalAccuracy = mostRecentLocation.verticalAccuracy
let horizontalAccuracy = mostRecentLocation.horizontalAccuracy
print("location is %#", mostRecentLocation)
print("verticalAccuracy: \(verticalAccuracy), horizontalAccuracy:\(horizontalAccuracy)")
}
Any suggestions why is this happening?
I'm in a room next to a window so i except to get bad accuracy but not that bad.
Thanks
I'm getting ridiculous results.
I got horizontalAccuracy of 15,000 m.
When i go out doors it works great but in doors should not be as bad as this.
Using Cellular triangulation and wifi should give a lot better results.
after 20 minutes i started to get good results of +- 50 m accuracy in doors.
I suggest you add a condition to make sure that you will just be using a location that have a better accuracy. On my case I use 20 as the desired horizontal accuracy on below example.
Example:
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
locationManager.stopUpdatingLocation()
if locations.last!.horizontalAccuracy < 20 {
//Only use location that enters here
}
else {
//If the accuracy is not met then start updating location again and if possible increase more the accuracy (use kCLLocationAccuracyBestForNavigation if you really need it). Make sure that you use the desired accuracy and filter properly to avoid draining battery.
locationManager.startUpdatingLocation()
}
}
I always have found that when you first start location updates, the first few readings are quite poor, and then the accuracy improves as the GPS settles down.
What I do is to first check if the timestamp on the location is more than a few seconds old. If it is, I discard it. (Not sure if recent OS versions still send "stale" GPS readings, but the system used to give you a location from the last time the GPS was powered up, sometimes several hours old.)
Once I get current locations, I check the accuracy, and discard any location updates who's accuracy reading is too poor. Only when I get a reading that's good enough do I use it (and stop location updates in your case, since you only want 1 update.)
Bear in mind that it can take 30 seconds (or more) for the GPS to settle down, and in an area with poor GPS signal, you may never get a good enough reading.
In an iPhone app that I'm building, GPS accuracy is a user-controlled value that can be set to either KCLLocationAccuracyNearestTenMeters or KCLLocationAccuracyHundred Meters. The code works fine to capture a track, but when monitoring the app in the Location Energy Impact Instrument I’m seeing some unexpected behavior. When accuracy is set to nearest 10 meters the app works as expected, however, if it’s set to 100 meters the setting remains OK for between a half and two seconds, as shown by the Instrument, but then it switches to KCLLocationAccuracy Best. This setting isn't an option in the app, or even a String anywhere in the code.
One twist here, I am running this as Swift 3.0 using Xcode 8, but it's working as it did before and the new platform doesn't seem to be an issue (and shouldn't have this kind of impact). It does mean that some API's have changed and may look different (and to my taste, better) below.
Obviously, this resetting has a very counterproductive impact on energy consumption, which shows in the Instrument which goes from Low to High energy usage at the point where it switches. I can't identify any point where the app would be doing this unintentionally - in fact, during this one-second period it should only be appending points returned by didUpdateLocations to a pending buffer for later processing, as shown below.
In a shared constants declaration:
let defaultTrackingAccuracy = kCLLocationAccuracyNearestTenMeters
let alternateTrackingAccuracy = kCLLocationAccuracyHundredMeters
var trackingAccuracy = kCLLocationAccuracyNearestTenMeters
var waypointInterval = 100
In a settings ViewController (can also reset waypointInterval but did not):
#IBAction func accuracySwitched(_ sender: UISwitch) {
if accuracySwitch.isOn {
Set.shared.trackingAccuracy = Set.shared.defaultTrackingAccuracy
} else {
Set.shared.trackingAccuracy = Set.shared.alternateTrackingAccuracy
}
}
LocationManager instantiation in a Model portion of code:
lazy var locationManager: CLLocationManager = {
var _locationManager = CLLocationManager()
_locationManager.delegate = self
_locationManager.desiredAccuracy = Set.shared.trackingAccuracy
_locationManager.allowsBackgroundLocationUpdates = true
_locationManager.distanceFilter = Double(Set.shared.waypointInterval)
return _locationManager
}()
Starting the location manager updates in the Model:
func setupLocationManager()
{
if CLLocationManager.authorizationStatus() != .authorizedAlways {
locationManager.requestAlwaysAuthorization()
if CLLocationManager.authorizationStatus() != .authorizedAlways {
delegate?.displayNotice("Unable to Capture Track", alertMessage: "This device requires authorization to use location services in order to capture a track. \n\nPress Continue to return to the Track List.", buttonText: "Continue")
}
}
if !CLLocationManager.locationServicesEnabled() {
delegate?.abortTrackCapture(.gpsUnavailable)
}
locationManager.startUpdatingLocation()
}
Processing points returned by the location manager instance, in the same Model portion:
#objc(locationManager:didUpdateLocations:) func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation])
{
assert(locations.first != nil, "didUpdateLocations called with empty array.")
if recordStatus == .record {
pendingPointsBuffer = pendingPointsBuffer + locations
}
lastPosition.latitude = locations.last!.coordinate.latitude
lastPosition.longitude = locations.last!.coordinate.longitude
lastPosition.elevation = locations.last!.altitude
}
Every few seconds, there is a routine that takes points from the buffer and posts them into a CoreData database, but that only accesses the buffer - it has no interaction with the location manager (so it can sleep through periods when the app is in background while the code above keeps loading points into the buffer).
The user interface is in a separate ViewController module, but shouldn’t be doing anything during the two seconds in question.
I'm thinking that there may be some OS based setting or process that could be doing this, but I haven't found anything that seems to do that.
Thanks for your input - any thoughts are appreciated.
I get latitude and longitude of the user in my method didUpdateLocations. If location is allowed I call a method that takes in parameters latitude, longitude, and calls a webservice, else I display an UIAlertView.
Problem is: iOS calls my locationManager delegate method a random number of times. So my webservice is called several times... How can I fix it please?
When I call the location, verify if is allowed... I make the request in the previous screen:
// GET LOCATION
self.initializeWaitingScreen()
if( CLLocationManager.authorizationStatus() == CLAuthorizationStatus.AuthorizedWhenInUse ||
CLLocationManager.authorizationStatus() == CLAuthorizationStatus.AuthorizedAlways){
self.locationManager.delegate = self
self.locationManager.desiredAccuracy = kCLLocationAccuracyBest
self.locationManager.startUpdatingLocation()
} else {
let loginFailAlert: UIAlertView = UIAlertView(title: "Localisation refusée", message: "Vos fonctionnalités sont restreintes, pour accéder à l'application complète, veuillez activer la localisation", delegate: self, cancelButtonTitle: "OK")
loginFailAlert.show()
self.initializeUIComponent()
self.initializeDataWithWebServiceWithoutLocation()
}
My locationManager method:
func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) {
var lon = manager.location.coordinate.longitude.description
var lat = manager.location.coordinate.latitude.description
self.locationManager.stopUpdatingLocation()
self.initializeDataWithWebServiceWithLocation(lon, _lat: lat)
self.initializeUIComponent()
}
self.initializeDataWithWebServiceWithLocation(lon, _lat: lat)
take longitude and latitude, and give it to my method who call webservices.
This is expected behavior. As CLLocationManager determines the user's location, updates will be sent (I don't just mean the obvious). See this excerpt from Apple's docs:
Regardless of which location service you use, location data is reported to your app via the location manager’s associated delegate object. Because it can take several seconds to return an initial location, the location manager typically delivers the previously cached location data immediately and then delivers more up-to-date location data as it becomes available. Therefore it is always a good idea to check the timestamp of any location object before taking any actions. If both location services are enabled simultaneously, they deliver events using the same set of delegate methods.
If you require some filtering of events, you'll need to (1) ensure you've set your desiredAccuracy properly to help minimize the number of events then (2) perform any particular app-specific filtering. Be cautious though, since the reason you get multiple updates is that the determined location has changed. If you second-guess the system, you may wind up with inaccurate data.
Finally, evaluate whether you need location changes or significant location changes. If you don't need the high granularity, go with "significant".