I am looking into using deferred location updates for an iOS activity tracker, which allows location services in background. I've implemented the suggested code snippets (see below). In Xcode debugging, deferred locations attempt to start a few times until location data comes in at about 1 per second. After that, it claims to succeed in starting deferrals, and the callback for the finish trigger also succeeds after the specified time period expires. However during the time, the location handler still runs once per second. I've read that this is because the phone hasn't deemed itself ready to enter the background, and that testing in Xcode does this. Note, AppDelegate's "didEnterBackground" eventhandler got called immediately when turning off the screen, and resumed when reopening app.
I ran the same code with the phone disconnected as another test, near the window with GPS, screen off, or switching to entirely different apps, and it still never actually defers the updates. I can tell because the networked update still comes in once every 30 seconds, instead of the interval of 120 seconds which is desired in the code sample below.
What else is needed to actually get deferrals to work, since there is no error occurring in starting them and they do get their finish callback? Why do location updates continue at 1 per second even when the app goes to background?
Iphone 5s, IOS 7.1.1
// .h file (partial)
#interface MotionTracker : NSObject<CLLocationManagerDelegate, UIAccelerometerDelegate>
#property (strong, nonatomic) CLLocationManager *locationManager;
#end
// .m file (parial)
- (id) init {
if(self = [super init]){
_locationManager = [[CLLocationManager alloc] init];
_locationManager.delegate = self;
_locationManager.distanceFilter = kCLDistanceFilterNone;
_locationManager.desiredAccuracy = kCLLocationAccuracyBest;
// if set to YES (default), app stops logging location at some point and doesn't resume in any timely fashion, all data points lost in between
_locationManager.pausesLocationUpdatesAutomatically = NO;
_locationManager.activityType = CLActivityTypeFitness;
}
return self;
}
// called early in program after login confirmed
- (void) startCollectingLocation {
[_locationManager startUpdatingLocation];
}
- (void)locationManager:(CLLocationManager *)manager
didUpdateLocations:(NSArray *)locations {
// logs to file when device is not in debug
// always returns 1
NSLog(#"Location update count: %d",[locations count]);
// some code here to handle location updates
// - collect key location day in NSDictionary
// - every N seconds send Network call to server to save (have tried 30 seconds, 15 minutes, 30 minute network intervals). Have also tried turning off network calls completely.
// deferred updates starter
if (!self.deferringUpdates) {
if([CLLocationManager deferredLocationUpdatesAvailable]){
[_locationManager allowDeferredLocationUpdatesUntilTraveled:500 timeout:(NSTimeInterval)120]; // (have also tried large numbers, and "Infinite"
self.deferringUpdates = YES;
NSLog(#"Deferred updates start");
} else {
NSLog(#"Deferred updates not available");
}
}
}
- (void)locationManager:(CLLocationManager *)manager didFinishDeferredUpdatesWithError:(NSError *)error {
if(!error){
_deferringUpdates = NO;
NSLog(#"Deferred updates: finished");
} else {
_deferringUpdates = NO;
NSLog(#"Deferred updates: %#", [error localizedDescription]);
}
}
If the device is connected to a debugger or on a charger, the device will remain powered (not sleep) and therefore will not enter deferred mode. Deferred mode is a power optimization allowing the device to sleep. If the device is not scheduled to sleep for other reasons, enabling deferred mode will not force it to sleep otherwise. Try your test by ensuring no other apps are using location services, and disconnecting it from a charger with the screen off. After running for some time, plug back in and check your logs, you should see that the device slept and deferred updates.
From Apple's
allowDeferredLocationUpdatesUntilTraveled:timeout: documentation:
Deferred updates are delivered only when the system enters a low power
state. Deferred updates do not occur during debugging because Xcode
prevents your app from sleeping and thus prevents the system from
entering that low power state.
It is also worth noting that deferred updates are only available when locationManager.desiredAccuracy is set to kCLLocationAccuracyBest OR kCLLocationAccuracyBest; locationManager.distanceFilter must also be set to kCLDistanceFilterNone.
From Apple's documentation:
...the location manager allows deferred updates only when GPS hardware is available on the device and when the desired accuracy is set to kCLLocationAccuracyBest or kCLLocationAccuracyBestForNavigation.
and
...the distanceFilter property of the location manager must be set to kCLDistanceFilterNone.
I have been struggling with the same issue, and I may have found an answer that solves this problem for many - at least it solves my problem and gets deferred updates working consistently for me.
I followed all of the steps in this list and no matter what I did, location updates would not defer. It occurred to me that I might have other apps running that were not allowing the system to sleep, so I killed all other apps in the multitasking tray. I ran my sample app again and ... it worked!
But the story doesn't end there. I tried again a little later, and even though there were no other apps running in the multitasking tray I couldn't get location services to defer. Then it occurred to me that I have an app on my phone called "Moves" which manages to keep itself alive even after you manually kill it. I'm not entirely sure how Moves comes magically back to life when you kill it, but it does (perhaps using bluetooth and the app preservation / restoration service). Even though it is alive and tracking your location it doesn't appear in the multitasking tray. I think that only apps that are manually launched appear in the tray - if the OS launches an app it doesn't appear in the tray. But I digress ...
I was able to get deferred location services to work consistently in my app by disallowing Moves to use location services. When I did, Moves complained even though it wasn't in multitasking tray. It seems that if another app is using location services (and not deferring) your app won't defer either.
Hi recently with the iOS 9 GM seed version out,I have seen location update(allowDeferredLocationUpdatesUntilTraveled:timeout:) not getting deferred.The same code used to work in iOS 8.4 and below versions.Its draining my device's battery by a huge margin.
Is there anything we need to explicitly set or mention for iOS 9?Didn't find anything from Apple documentation
Here is the code that I implemented.
-(void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
if (!self.deferringUpdates) {
[self.locationManager allowDeferredLocationUpdatesUntilTraveled:CLLocationDistanceMax timeout:30];
self.deferringUpdates = YES;
} }
-(void)locationManager:(CLLocationManager *)manager didFinishDeferredUpdatesWithError:(NSError *)error { // Stop deferring updates self.deferringUpdates = NO;
}
I also set the allowsBackgroundLocationUpdates property but even that didn't help. self.locationManager.allowsBackgroundLocationUpdates=YES;
In iOS 9 and later, regardless of deployment target, you must also set the allowsBackgroundLocationUpdatesproperty of the location manager object to YES in order to receive background location updates. By default, this property is NO, and it should remain this way until a time when your app actively requires background location updates.
https://developer.apple.com/library/prerelease/ios/documentation/Performance/Conceptual/EnergyGuide-iOS/LocationBestPractices.html
Please let me know what additional I need to make
Thanks
Related
I am trying to make an app to track the user GPS all the time, this app is a kind of car GPS tracker to get the location of driver all the time and send it to server.
I have tried to add "location updates" to the "background modes" but the app will automatically suspends after 10 mins when going into background.
Is there a way to make this app run all the time and get the GPS location?
You have two options here:
1) Regular location tracking. This type of tracking works with kCLAuthorizationStatusAuthorizedWhenInUse and kCLAuthorizationStatusAuthorizedAlways authorizations. When CLLocationManager started tracking location once it will receive location updates in delegate method locationManager:didUpdateLocations:. App can go to suspended state, but when location manager receive new location app goes to background state and handles new location in delegate method. How to setup location manager:
- (void)viewDidLoad {
[super viewDidLoad];
self.locationManager = [[CLLocationManager alloc] init];
// Setup location tracker accuracy
self.locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation;
// Distance filter
self.locationManager.distanceFilter = 50.f;
// Assign location tracker delegate
self.locationManager.delegate = self;
// This setup pauses location manager if location wasn't changed
[self.locationManager setPausesLocationUpdatesAutomatically:YES];
// For iOS9 we have to call this method if we want to receive location updates in background mode
if([self.locationManager respondsToSelector:#selector(allowsBackgroundLocationUpdates)]){
[self.locationManager setAllowsBackgroundLocationUpdates:YES];
}
[self.locationManager startUpdatingLocation];
}
2) Signification location changes tracking. This type of tracking works only with kCLAuthorizationStatusAuthorizedAlways authorization. It receives new location only each 500 meters, so distance filter and desiredAccuracy don't work here. App can go to suspended state, and even can be terminated by system, but when location updates app goes to background state and receives location in delegate method locationManager:didUpdateLocations:.If app was terminated by system, it will be relaunched in background with UIApplicationLaunchOptionsLocationKey key in launch options in didFinishLaunchingWithOptions app delegate method. How to setup this type on tracking:
- (void)viewDidLoad {
[super viewDidLoad];
self.locationManager = [[CLLocationManager alloc] init];
// Assign location tracker delegate
self.locationManager.delegate = self;
// For iOS9 we have to call this method if we want to receive location updates in background mode
if([self.locationManager respondsToSelector:#selector(allowsBackgroundLocationUpdates)]){
[self.locationManager setAllowsBackgroundLocationUpdates:YES];
}
[self.locationManager startMonitoringSignificantLocationChanges];
}
You should notice that both of these methods does not guarantee that your application does not go to suspended state.
Also, if app was terminated by user (for example from app switcher by swipe) location tracking in background will not work.
UPDATE (corresponding to comments)
Here is my code examples that work for me:
For Regular tracking. Run the example, provide access to user location, tap Start button to start location updates. To test locations in simulator choose in simulator menu Debug > Location > Freeway Drive. Now you can push app to background by home button (Command+Shift+H). Leave simulator for more than 10 minutes, and all this time app will receive locations. When you return to app you will see red pins on the map.
For Significant changes. Run the app and test by the same way as for previous example.
Monitoring Significant changes can be started only by method [self.locationManager startMonitoringSignificantLocationChanges];
UPDATE (iOS 11)
Changes to location tracking in iOS 11
iOS 11 also makes some major changes to existing APIs. One of the affected areas is location tracking. If your app only uses location while the app is in the foreground, as most apps do, you might not have to change anything at all; however, if it’s one of those apps that continuously track user’s location throughout the day, you should probably book some time this summer for making some changes in how you do the tracking and testing possible usage scenarios.
follow this link: https://mackuba.eu/2017/07/13/changes-to-location-tracking-in-ios-11/
I am sure it is useful for the author because the question was asked in Feb 2016 and I am giving an answer in June 2019. This answer maybe is useful for other users.
Recently, I was working with the same requirement. After 2-3 week hard work, I did it. For other users, I create a helper class for it. Which is available in GitHub.
Please use HSLocationManager for your requirement. I have achieved the same requirements in one of my project
Location manager that allows getting background location updates every
n seconds with desired location accuracy.
Advantage:
OS will never kill our app if the location manager is currently
running.
Give periodically location update when it required(range is between 2 -
170 seconds (limited by max allowed background task time))
Customizable location accuracy and time period.
Low memory consumption(Singleton class)
In reply to comment 1 in the solution (I can't comment anywhere yet): you didn't seem to solve the problem as your app gets suspended and doesn't update the location any more after 10 minutes.
I had the same issue: I had set setAllowsBackgroundLocationUpdates to YES, and I had the NSLocationAlwaysUsageDescription key in my Info.plist, but my App also used to stop tracking location after 10 minutes.
I solved it by adding both NSLocationAlwaysUsageDescription and NSLocationWhenInUseUsageDescription to the Info.plist file so it looks like this:
<key>NSLocationAlwaysUsageDescription</key>
<string>This app needs to use your location</string>
<key>NSLocationWhenInUseUsageDescription</key>
<string>This app needs to use your location</string>
set it.it take power of battery but your application run in Background.OS does not Suspend your App
[self.locationManager setPausesLocationUpdatesAutomatically:NO];
Hi recently with the iOS 9 GM seed version out,I have seen location update(allowDeferredLocationUpdatesUntilTraveled:timeout:) not getting deferred. I am getting error kCLErrorDeferredFailed - The location manager did not enter deferred mode for an unknown reason.
Its because of this error its not entering the defer mode at all and location updates are firing continuously .
The same code used to work in iOS 8.4 and below versions.Its draining my device's battery by a huge percentage.
Is there anything we need to explicitly set or mention for iOS 9.Didn't find anything from Apple documentation?
-(void)locationManager:(CLLocationManager *)manager
didUpdateLocations:(NSArray *)locations {
if (!self.deferringUpdates) {
[self.locationManager allowDeferredLocationUpdatesUntilTraveled:CLLocationDistanceMax timeout:30];
self.deferringUpdates = YES;
}
}
-(void)locationManager:(CLLocationManager *)manager
didFinishDeferredUpdatesWithError:(NSError *)error {
// Stop deferring updates
self.deferringUpdates = NO;
}
I also set the allowsBackgroundLocationUpdates property but even that didn't help.
self.locationManager.allowsBackgroundLocationUpdates=YES;
In iOS 9 and later, regardless of deployment target, you must also set the allowsBackgroundLocationUpdatesproperty of the location manager object to YES in order to receive background location updates. By default, this property is NO, and it should remain this way until a time when your app actively requires background location updates.
Reduce Location Accuracy and Duration
Please let me know what additional I need to make
Thanks
Please read the discussion on the API reference page.
A few things to try, as mentioned here
Kill all apps from multitasking bar
Verify that no other app is using location services
Unplug the device from debugger and MacBook (Verify it is still getting call by logging didUpdateLocations to a file)
Make sure that the device supports deferred updates
Make sure that the distanceFilter is None, the desiredAccuracy is Best
I am working on a location services app and am finding some strange behavior. Once the user confirms using location services, the geofence icon appears in the status bar. Everything works great and I get enter and exit region events whether the app is running, in the background, or not in the background. But at some point the geofence icon disappears and my device is insensitive to the Beacon. Are there any conditions under which the geofence is disabled until I power cycle the device? And power cycling does bring it back.
This is a newly introduced bug in CoreLocation. Unfortunately, there is no known automated way to fix this. It requires a power cycle or Bluetooth off/on sequence to resolve.
See here.
I was having a similar problem. My app would work and locate beacons on initial run. When I rebooted, app opened to ScanViewController as expected but did not detect beacon.
I referenced article on StackOverflow, iBeacon: didRangeBeacons stops getting called, must reset device for it to work again and reviewed Apple's WWDC 2013 Video Session "What's new in Corelocation" https://developer.apple.com/videos/wwdc/2013/index.php?id=307
I found additional CLLocation delegate methods:
When you init your beacon region if you set:
notifyEntryStateOnDisplay = YES;
//The following delegate method will be called:
-(void) locationManager: (CLLocationManager *) manager didDetermineState:(CLRegionState)state forRegion:(CLRegion *)region {
if (state ==CLRegionStateInside) {
[_locationManager startRangingBeaconsInRegion:region]:
}
//Your alternative code
}
//To help trouble shoot, I added this delegate methods
-(void) locationManager:(CLLocationManager *)manager monitoringDidFailForRegion:(CLRegion *) region withError: (NSError *)error {
}
and
-(void) locationManager:(CLLocationManager *)manager rangingBeaconsDidFailForRegion:(CLRegion *) region withError: (NSError *)error {
}
I ran app. It returned no failure errors. I checked settings. Bluetooth was enabled and detecting BT devices.
I checked the status bar for geofencing icon. The geofencing icon was present.
I waited for over 2 minutes and then the app detected the beacons and worked as expected. Sluggish is an understatement. I knew that rebooting should work according to all the iOS 7.1 articles that I read in StackOverFlow and other resources.
I rebooted and waited for the app to detect the beacons. On average it took 2 minutes until beacon detection. I am not sure what is causing this slow response. Since must app responses are measured in fractions of seconds, I am sure that developers may think that their apps are not working.
I suggest if your app does not detect beacons or return failure errors that you wait 2 minutes to see if you app will detect the beacon(s). I hope this helps.
Testing Device: iPhone 5 (iOS 7)
I have an app that uses RegionMonitoring and updateLocation. If a region is entered, didEnterRegion is called as expected. Then I call startUpdatingLocation. But the method didUpdateToLocation is only called 10-20 times while it should update the location until the timer fires.
The relevant code:
CLLocationManager *_locationManager;
NSTimer *_timer;
-(void)initLocationManager
{
_locationManager = [[CLLocationManager alloc] init];
_locationManager.delegate = self;
[_locationManager setActivityType:CLActivityTypeOther];
[_locationManager setDesiredAccuracy:kCLLocationAccuracyBestForNavigation];
[_locationManager setPausesLocationUpdatesAutomatically:NO];
[_locationManager setDistanceFilter:kCLDistanceFilterNone];
}
//Did Enter Region, called as expected:
- (void)locationManager:(CLLocationManager *)manager didEnterRegion:(CLRegion *)region
{
[_locationManager startUpdatingLocation];
_timer = [NSTimer scheduledTimerWithTimeInterval:300.0f target:self selector:#selector(scheduleMethod:) userInfo:nil repeats:NO];
}
//Timer Fire Method:
- (void) scheduleMethod:(NSTimer*)timer
{
[Utils writeToLog:#"Timer-Stop"];
[_locationManager stopUpdatingLocation];
}
//This Method only called 10-20 Times (in the first 10-20 Seconds) and not the complete 5 Minutes:
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
[Utils writeToLog:#"LocationUpdate!"];
}
So far I tried:
Restarting the Updates in the locationManagerDidPauseLocationUpdates method, but it seems that this is never be called:
-(void)locationManagerDidPauseLocationUpdates:(CLLocationManager *)manager
{
[WRUtils writeToLog:#"LocationUpdate paused, restarted"];
[_locationManager startUpdatingLocation];
}
Check for errors in the didFailWithError method, but this is not called either.
And played a bit with the properties:
[_locationManager setActivityType:CLActivityTypeOther];
[_locationManager setDesiredAccuracy:kCLLocationAccuracyBestForNavigation];
[_locationManager setPausesLocationUpdatesAutomatically:NO];
Plist settings are right I guess:
Required background modes YES
Required background Modes
Item 0 App registers for location updates
How can I solve this?
Apple has introduced a new policy in iOS 7. iOS 7 does no longer deliver location updates in the background if you call „startUpdatingLocation“ while the App is in the background. You only get update when the App is brought to the foreground in this case.
When you’re using the geofencing feature, your App just gets a few seconds each time you get a RegionEntered/Exited notification to process this notification. And in these few seconds you may also get location updates. After these few seconds are over iOS 7 just suspends your App again.
You can use background task to get more than just a few seconds, but in iOS 7 Apple has also reduced the time Apps can run in the background from 10 minutes (iOS 6 and older) to only 3 minutes under iOS 7. It looks like that these 3 minutes are the total amount for the whole time the App is in the background. Which means you can not ask iOS 7 10 times to get 1 minute background time, you’ll only get 3 minutes in total, so after the 3rd time you’ve asked for a minute, your App won't get any background time anymore at all.
Your only chance in getting location updates in the background is to call „startUpdatingLocation“ while the App is in the foreground. This is sad especially when you only need location updates in response to Region(Enter/Exit messages, because you need to let the location updates running all the time. But you can at least reduce the battery usage by setting the accuracy value to kCLLocationAccuracyThreeKilometers when
you do not need location updates and set the accuracy to kCLLocationAccuracyBest only when you really need the geo coordinates. The iOS won’t power up GPS for the kCLLocationAccuracyThreeKilometers value, so the battery usage would be moderate in this case.
Also the value kCLLocationAccuracyBestForNavigation for the accuracy seems to cause problems under IOS 7. I do not get any location updates with this value if the device is not connected to a an external power supply.
All in all the new iOS 7 policy for location updates is making it much harder to develop certain kinds of Apps. Instead of registering for location updates only when needed, you are forced to register for these for the while lifetime of your App. Which of course drains the battery a little bit faster, though Apple’s intension for this new policy was probably the opposite.
UPDATE:
After some more testing I’ve found some kind of solution for the problem.
The docs from Apple mention that when using the Significant Location Change API, Apps can receive location updates in the background even if „startUpdatingLocation“ is started in the background.
My first tests didn’t work well. I was registering my App for significant location updates within the region monitoring delegate methods just before calling startUpdatingLocation (so this location service is only enabled when needed), but this still does not deliver location updates in the background as the docs would suggest.
But if you start listening for significant location changes directly after your App is launched (and never switch this off), you can call start „startUpdatingLocation“ while the App is in the background and also receive location updates in the background. The battery usage of having the "significant location change“ feature on all the time seems to be very low, so this will be probably the solution for most Apps.
You have to check if the „significant location change“ feature is available on the device, but it seems that all current devices do support this. Even the 5th generation of iPod Touch does support it (The iPod Touch can not use cell towers for location updates, which is the base method of this feature according to the docs from Apple, so I guess we can assume that all current devices running iOS 7 can use the „significant location update“ API. Though it’s probably a good idea to check if this feature is really available, maybe there are certain circumstances where the feature is not available).
Using the "significant location change“ API might have one disadvantage: The App can be launched in the background (if it was terminated in the background by the iOS to reuse its memory for other Apps) repeatedly and unnecessarily whenever the device has moved „significantly“ (according to the docs: when the cell tower has changed, but no more than once per 5 min). So Apps which only need to be activated, when a certain region is exited or entered, will be launched and informed about location changed all the time, not only at those regions. But I assume this should be still much better than having standard location updates active all the time.
My iPhone 5s drains the battery only 1% over night with the significant location changes active, instead of 12% with having the standard location updates active with the accuracy set to 3km.
Hope this helps all developers who are struggling with the new iOS 7 behavior.
In background timer will not run, so here your timer object will not respond, You need to create background task handler, check comment of below link,
How to run the timer in background of the application?
In background if you want to continue location service than you need to set pausesLocationUpdatesAutomatically flag, flag info on
pausesLocationUpdatesAutomatically flag info
if ([self.locationManager respondsToSelector:#selector(pausesLocationUpdatesAutomatically)]) {
self.locationManager.pausesLocationUpdatesAutomatically = NO;
}
check my comment on
Location service going to "Inactive" state in iPhone 5
For location manager there below are the CLLocationManagerDelegate methods for location update,
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation [Deprecated in __IPHONE_6_0]
- (void)locationManager:(CLLocationManager *)manager
didUpdateLocations:(NSArray *)locations __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_6_0);
Where you found
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation ??
Use below code in your didEnterRegion Method to start updates again
[_locationManager startMonitoringSignificantLocationChanges];
if ([_locationManager respondsToSelector:#selector(setAllowsBackgroundLocationUpdates:)])
{
_locationManager.allowsBackgroundLocationUpdates =YES;
}
[_locationManager startUpdatingLocation];
To save power in my app I have decided to use a mix of startUpdatingLocation when the app is active and go into startMonitoringSignificantLocationChanges mode when the app is in the background. Basically I do the following when the app goes into the background:
-(void)applicationDidEnterBackground:(UIApplication *)application{
[myLocationManager startMonitoringSignificantLocationChanges];
}
And when the app comes back into the foreground I do the following:
-(void)applicationDidBecomeActive:(UIApplication *)application{
//Other irrelevant code
[myLocationManager stopMonitoringSignificantLocationChanges];
[myLocationManager startUpdatingLocation];
}
This seems logical, to me anyways. My question is, should I be calling the stopUpdatingLocation method in the applicationDidEnterBackground event? Like so:
-(void)applicationDidEnterBackground:(UIApplication *)application{
[myLocationManager stopUpdatingLocation];
[myLocationManager startMonitoringSignificantLocationChanges];
}
Where exactly should I be calling the stopUpdatingLocation method?? Please tell me if there is more than one place where this should be done. I'm assuming any error event should stop the updating?
I don't see anything wrong with what you are doing. Note that I have a commercial app that heavily uses location services, and I'm in the midst of rewriting it to improve it's performance and minimize battery usage.
My released version uses sigLocationChanges predominantly (in background & foreground), but switches to using startUpdatingLocation when unhappy with the quality of the location sigLocationChanges gives me, since my UI has to display the users location roughly accurately. I call stopUpdatingLocation immediately after each event to minimize battery drain. In my shipping version this seems to work okay, but my log files have found a tiny subset of users who seem to constantly get poor locations and I'm spinning up the GPS hardware more than I like.
Also in Privacy Settings, the type of location icon displayed for your app will be determined by when you last used the full GPS location mode. Mine always shows the location icon that indicates a heavy battery impact, even if I'm only using startUpdatingLocation briefly a couple times per day, which can make my users paranoid about how my app affects their battery life.
In my new release, to minimize the battery drain of using of startUpdatingLocation, I've cut it's use back to hopefully nil. When the app activates, I now get the current location directly from the location manager, cLLocMgr.location. Typically that's an accurate location, and my UI can be instantly drawn (or refreshed) correctly. I also check it again when certain views are activated to ensure if the user is moving while keeping my app open the display keeps up. Now I only spin up the GPS hardware if the phone has a bad location in a specific situation where a good location is absolutely required in the app. In that case, I limit it's use to 2 minutes (I'm assuming 2 minutes is long enough to get best location from GPS hardware), and wait at least 10 minutes before allowing it's use again.
Your question doesn't give me enough info to tell how accurate you need to be and how dynamic your location display is. But unless you need super accuracy and dynamic display, you should consider just using the current location without spinning up the GPS hardware to save battery.
Edit: Here is the actual code I used for Jeraldo, cleaned up a bit. Note it's been a year since I touched it, so I'm a little rusty on it, hope I didn't clean up anything.
// Called at start to ask user to authorize location data access.
- (void) requestIOSLocationMonitoring {
#if TARGET_IPHONE_SIMULATOR
// If running in siumaltor turn on continuous updating (GPS mode)
// This is for testing as significant change isn't useful in simulator
// Set a movement threshold for new events. This is only used by continiuous mode, not sig change events
// Keep it as low as possible,but not so low as to generate spurious movements.
cLLocMgr.distanceFilter = 30;
// Use continuous location events in simulator.
// desired accuracy only works in continuious (high power) mode.
cLLocMgr.desiredAccuracy = kCLLocationAccuracyBest;
[cLLocMgr startUpdatingLocation];
#else
// If not in simulator app's default is significant change monitoring
[cLLocMgr startMonitoringSignificantLocationChanges];
#endif //TARGET_IPHONE_SIMULATOR
}
// Toggle back and forth between continius updates (GPS on) and
// significant change monitoring
- (void) setGPSMode: (bool) useGPSMode {
// Keep track of time since we last changed GPS mode
NSTimeInterval secsInThisMode = [[NSDate date] timeIntervalSinceDate: lastModeChange];
// inGPSMode is an object instance variable app uses to track mode it is in.
if (inGPSMode != useGPSMode) {
lastModeChange = [NSDate date];
if (!useGPSMode) {
// Tell app to operate as if continuous updating is off
inGPSMode = false;
#if TARGET_IPHONE_SIMULATOR
// But keep using continuous location events in simulator for testing.
cLLocMgr.distanceFilter = 30;
#else
// Turn off continious updates for app on actual devices
[cLLocMgr stopUpdatingLocation];
#endif
} else if (secsInThisMode > cMinGPSModeBreak) {
// Only turn on continuous updating again if it's been off long enough
// Prevents GPS mode from running continiously and killing battery life
inGPSMode = true;
cLLocMgr.desiredAccuracy = kCLLocationAccuracyBest;
cLLocMgr.distanceFilter = kCLDistanceFilterNone;
[cLLocMgr startUpdatingLocation];
}
}
}