For the sake of this question, assume I plan to build a Google Latitude client app for iOS 4.
my app needs to upload the user gps location every two minutes, and also download the user friends locations. - in the background!
my app can't wait to be woken up by the OS on cellular tower switches (because they may only happen after 2 KM, while my app needs constant gps updating), so I understand I can create a thread, similar to the ones GPS navigators use, to run in the background.
I have no knowledge in iPhone programming, I just need to know if my app is feasible.
Will I be able to access the internet from within the background thread (and upload the user gps location), or is it restricted to only sampling the GPS location.
1.
Will Apple approve such an application, or is this type of use forbidden? because my app isn't realy critical such as a gps navigator
Thanks!
As Don said, iOS will send location events to apps that support it. From there, the app can do what it needs to do with the location event.
Background apps can register for one of three options:
Significant changes only: a low-power way to track location that only wakes the app up when there's a "significant" change in location
Standard location services: compatible with all iOS devices that can use location services, allows you specify change in distance, and works in background. However, if the app has been terminated or suspended, iOS won't attempt to relaunch the app.
Continuous location services: allows the program to receive continuous location updates and iOS will not suspend the application when sent to the background.
More info: Executing Code in the Background and Location Awareness Programming Guide
If you take a look at Executing Code in the Background, Apple provides guidelines on what multitasking-aware apps should and shouldn't do.
You will receive the locationManager:didUpdateToLocation:fromLocation: message in your app. In there, you can do whatever you need to, although you should not update the UI or use Open GL if your are in the background.
Related
Am developing application for calculate count of user moved steps and draw the user activities in the map. And we are using UIAccelerometer delegate for receive acceleration-related data from the onboard hardware. So I need to receive acceleration-related data when the application in background mode too. Last time one of my application got rejected because of using location service in background, Apple suggested me like "you can only use this background mode if your app truly needs this information to provide value for the user". Kindly suggest the best approach for this application.
You cannot run accelerometer in background.
You can track user's location in background... however, if you just keep tracking it and do nothing with that info.. apple is going to reject it and tell you to just get the lates location when app comes to foreground.
what you can try is.. update the user of total distance covered etc on a regular basis (like run keeper) and this will justify tracking location in background.
But first, you can try appealing to the review board explaining that you need to track location in background because you show entire route travelled by user when app comes to foregraound. and compare this to existing apps like run keeper and if you are lucky apple may approve your application without any changes...
This can easily be done.
What happens in that iOS put your application in halt state when your application is not in running in foreground state.
You just need to register your application for background execution.
Refer :
http://dcraziee.wordpress.com/2013/05/20/background_ios/
Also refer :
iOS background application network access
for apple policies about using location service.Which states that you can use location service in background.
I am using CoreLocation to determine user's location to calculate the distance and show the route on the map. To minimize battery usage I am turning off GPS after getting location and turning it on again after 1 minute. When the application is active everything works fine, but after sending it to background and turning off GPS, the app seems to be inactive at all, it doesn't output anything (using NSLog()). I have added directive to info.plist file to allow the application to run in background. When I don't turn off the GPS in background the app works as well as in foreground.
So my question is the following: does GPS always need to be turned on in background to prevent the application to be suspended or there is another workaround (because the turned GPS drains the battery)?
P.S. I am new to iOS and mobile development at all, so maybe there are some tips that I have to know.
See http://developer.apple.com/library/ios/#documentation/iphone/conceptual/iphoneosprogrammingguide/ManagingYourApplicationsFlow/ManagingYourApplicationsFlow.html
Apple does not support long running background task in general.
This does only work for specific tasks:
audio,
location,
voip,
newsstand-content,
external-accessory,
bluetooth-central and
bluetooth-peripheral
When you do not use any of that, your app could be suspended.
In your case ypu have specified location, but disabled the location update. Then for apple there is no reason to keep your app in background mode.
I have to develop a kind of GPS navigation application that needs to constantly keep track of the position of the user, which is moving by car.
In the specific, I don't have to display the current location on a map but just to record its position with the best possible precision in order to calculate the total distance traveled.
Of course the application needs to continue its work in background if the user switch to another app, a phone call come in or something like that…
From the tests I have made and from what I have learned from this useful post (and from the documentation), it seems to me that the best choice in this case is the Standard location service, with the application configured with the UIBackgroundModes = location in the .plist file.
In this way it will continue to receive the location updates even if in background and it will never be suspended by the OS (this is actually true only if [locationManager startUpdatingLocation] has been called). This is also confirmed by this guys.
I have personally verified that is true simply by running the app with Instruments and the Memory monitor module where you can see the various flags about the app states, putting the app in background first with UIBackgroundModes set to location and startUpdatingLocation active, and after without it.
1) I'm now wondering what to do when the app is terminated when it is tracking the position. I don't want to loose any location updates so I need to wake up it again whenever a new update is available.
The documentation say:
Important: The applicationWillTerminate: method is not called if your
app is currently suspended.
But because in my case it will be never suspended (it will stay in background but not suspended), my logical conclusion is that applicationWillTerminate will be always called and so I could register for a Significant location update or Region monitoring inside of this method in order to be waked up and then restart the Standard location service.
Is applicationWillTerminate the right place to put this code?
2) An application working in background but not suspended could be terminated by the OS for no other reasons than a very low memory condition or for my app don't properly respond to a memory warning? (the user could also manually close it). I was concerned if applicationWillTerminate wouldn't be called in some way.
3) Could Apple not approve an app which constantly use the standard location services in background because of its quick battery drain?
Have you ever had approve problems for similar apps?
since you are asking many questions which you shoukd not do here, i cam give you only aswrs to a part of it.
if the app is terminated, then you cannot restart it anymore.
This is usually the case when the user terminates the app.
Dont worry Apple ( ios) will not terminate your app. your app will not use much memory, games with huge bitmap graphics are more likely to be termin.
evry gps app will drain the bat. that is not a reason for not aproving.
suspended means that app is not in background mode, it is sleeping. you will not receive Gps, so there is no need to call you on terminate. you have to save data before, see the apple docu on background modes and app life cycle.
I have created this location tracking app, that uses nstimer in background to fetch location every 4 mins.
I am wondering if there will be any problem in submitting the app in the market place..
If you know something regarding it, can you please let me know.
Thanx.
If it's relevant to what your app is doing I don't think it will be a problem.
This is from Apple's App Store Review Guidelines:
4.1 Apps that do not notify and obtain user consent before collecting, transmitting, or using location data will be rejected
4.2 Apps that use location-based APIs for automatic or autonomous control of vehicles, aircraft, or other devices will be rejected
4.3 Apps that use location-based APIs for dispatch, fleet management, or emergency services will be rejected
4.4 Location data can only be used when directly relevant to the features and services provided by the app to the user or to support
approved advertising uses
But pay attention that if you want your app to keep getting location updates even in background, you need to declare this in your plist file, otherwise when the app goes to background you won't be able to get location updates.
Declaring Your App’s Supported Background Tasks
Support for some types of background execution must be declared in
advance by the app that uses them. An app declares support for a
service using its Info.plist file. Add the UIBackgroundModes key to
your Info.plist file and set its value to an array containing one or
location—The app keeps users informed of their location, even while it
is running in the background.
I've gotten one app through. You have to make sure that the user is informed exactly as to what is going on. So dialogs have to be very specific and have a privacy policy in place.
4 minutes is a little bit extreme if that's a permanent state of your app.. I don't think Apple would allow that if they found it during app review. Would it not suffice to just have it updated based on movement? ie. the significant location change api?
The app I did this for used significant location change api for background location tracking and then stepped it up to higher frequency tracking if the app was actually open.
I am developing an iphone app. the iphone which install my app was asked to upload it's location every minute(or hour) to a webservice. So what should i do with this situation?
I know there is a corelocation framework, I could use it for my app. like when I run this app, the corelocation will grab the GPS for my. my question is what if I close the app? Can i still get the GPS and upload it to webservice every minute? If I can't, how could I ?
You could enable background location service, If application is in background and receives a considerable change in location it will activate the app for a brief amount of time, This will give you some time to process. Apple recommends not to use web-service calls during this time, because there wont be any guarantee that the app would be live when it returns back. But since you just want to update the location, you could just post it and dont have to wait for response. Please note that significant location change should be used and this will help you to save your device's battery life. This is when the app is in background state.
May be you could try registering for the proximity/location alert or something. But i am not sure whether it would help when app is closed.
If your app is running in the background then you can get the GPS data but it the application is removed from the Background then you cannot get the GPS data. This is not possible in iPhone.