I have a location based application that needs to run in the background. I have several iPhones that I am testing on including a older 3G. I register my app to need background location based services and everything works as advertised accept with the older 3G phone. When you press the lock button, it does an applicationWillResignActive: as expected, unfortunately the phone immediately goes into low power mode and that is that. When you have the phone tethered with the USB cable, and then press the lock button, the 3G phone stays alive and correctly reports location changes. When it is disconnected, it goes immediately into low power mode.
The strange thing is that I am pretty sure that it used to work. I want to see if anyone out there has an app running on an older iphone (3G) which registers for location services and is not immediately put into lower power mode when the lock button is pressed. If so, what am I doing wrong.
I followed all the directions, have locations in my Info.plist.
Thanks for your help!
Cheers,
Bryan
I think you are seeing expected behavior.
I noticed on a recent trip with my old 3g the Location Manager appeared to remain active only when the usb supplied power. On usb, unlocking the phone would bring the app up (google maps in this case) immediately with Location Manager active. Without usb, I had to relaunch Location Manager each time I unlocked the phone.
I strongly suspect this is safety/power-saving feature. The Location Manager sucks battery life at a startling rate, especially on older devices. By running the Location Manager continuously while on battery, you could easily flatline a user's phone without their knowledge.
I would be very leery of any design that requires the Location Manager to run continuously in the background. Test it throughly.
You don't want the economic consequences of users deciding that "when I use Bryan's app, my battery mysteriously dies" or the moral consequences of leaving someone in an emergency without a working phone.
Related
I am working on Location Tracking Application. This application continuously send location even in background. I am using SLC property.
I am also using silent push trick for location tracking. Logic of Silent push:
Check AppIconbadge number and perform the action according to AppIconbadge number. I have a timer which check AppIconbadge at every 10 seconds.
Now this is the case:
Device is on SLC and put the app in background and turn off the device. While you switch back to On this device it is still reporting on SLC while Ping (Silent Push) is not working.
I have started the timer when app get SLC trigger. But its not working.
Can you help?
You can't do it.
The way iOS achieves great battery life and reduces RAM usage makes this kind of thing impossible.
Your only real possibility is to have your server send occasional push notifications to the device, and have your app on the device respond with its location. This is how Find My Phone and Find My Friends both work. The idea is to improve battery life by doing as much as possible on a server, which has mains power and virtually unlimited RAM, instead of on the phone which only has a battery and might need all it's RAM to play a 3D game
Basically the CPU is not running at all most of the time, so it can't schedule stuff to run periodically, and you can't rely on there being enough RAM available to run your app so it also can't be running all the time even if the CPU is powered on.
According to the WWDC 2013 keynote, push notifications are much more powerful on iOS 7, so you should look that up (I haven't looked into it myself, just saw the keynote.
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 am developing an iphone application and I think that it's business logic requires a service to be always running in background.
The service needed is to get the acceleration of the device and notify or perform a certain action when that acceleration becomes a certain value.
Is that allowable in the Apple policies, or is there any idea about a solution?
What cydia development possibilities to help me ?
Dbramhall left out one important thing:
You can't guarantee that your app won't be killed, the OS can kill apps that are in the background at will if it requires more memory.
So if at all possible i wouldn't rely on making sure it can run its process in the background and before you ask "How can i stop this?". Well you shouldn't I've never tried it myself because i don't know the effects it has on the OS.
Also if you stop it from being killed in the Background, if it is going to be on the app store then it won't pass evaluation process, because it breaks the OS
Well, an application can run in the background and Apple perfectly accepts this however the user will obviously be be able to close the application (or should be able to) via the multi-tasking bar and this will end the application. Period.
Apple will not accept an application that runs constantly regardless of whether the user has is in background state as this drains the battery, heats the device etc. So an application can run in the background so long as the user can quit it when close it from the multi-tasking bar however it cannot continue to run after the user closed it via multi-tasking - if it does continue, Apple will reject the application.
Also, see 2.16 of the Apple Store review guidelines: https://developer.apple.com/appstore/resources/approval/guidelines.html#functionality
I'm having trouble keeping wifi from disconnecting after 30 mins in an iphone app that needs to function when locked by the user.
The app normally does not sleep, but if the user so chooses they may lock the display. I'm adding a new feature to the app that sends data out over the network at 1 second intervals. prior to this there has been no network requirement for the app, and it has functioned as desired (music, timer-based processes) while user-locked.
The answer seemed to be here:
Wifi connection doesn't stay alive when asleep, with iOS4
But adding UIRequiresPersistentWifi boolean to info.plist doesn't keep it from timing out the wifi (i'm testing on Touch, iOS4.02) after 30 mins, even while the app is busy sending data out over the connetion. Maybe this only applies if the display sleeps itself, rather than user locks?
Related, I think there is no way to "stir" the display at any interval? User pressing the home button is sufficient to bring back the wifi; unlocking is not necessary.
Also, I've read on the interwebs that it was stated in a WWDC that UIRequiresPersistentWifi applies to keeping alive 3G as well. Can anyone verify?
thanks
Your app may be getting suspended by the OS after a long enough period of user inactivity.
Under iOS 4.x there are certain types of apps that aren't suspended when the display is locked (music player, VOIP, etc.) Apps that register as a VOIP type app might be allowed to keep a persistant network connection over a longer period. However Apple may require that an app actually provide some VOIP functionality in order to register for that type in any app submitted for review.
Is there some activity that you need to perform network activity? From iOS5 onwards, we have noted that even if we send network packets (heartbeat timers), then also iOS 5 blocks it after locking device.
It is to be noted that services which requires VoIP continue to receive calls, and notifications do come when your phone is on sleep mode or locked. This means that WiFi is not totally closed. I dont know how this happens.
As an alternative you can use data carrier of your network provider as an alternative to WiFi in case WiFi has gone down. With UIRequiresPersistentWiFi, you just inform iOS5 that you would require WiFi to run your application, nothing else signifies whether it keeps your screen ON or OFF. For keeping your phone from autolock you can however use disableTimer = YES flag, in lieu of your battery charge.
I have a requirement in my iPhone app that I know when somebody running the same app is close by.
I'm thinking that GameKit using Bluetooth would let me do that. GPS location is not precise enough in this particular case.
However, if the user closes the app then the function won't work anymore. Even under iOS4, the task switching will close down the BonJour services so I can't have the app run in the background.
Seems to me I can only have this function if the user leaves the app up and running. Would you agree? Or is there a different approach I can take?
People are very concerned with privacy, so they would naturally expect such privacy invading functionality to be switched off when they close down the application.
If they choose to have this feature enabled, then it's a different matter. Then they expect that somebody else may locate them.
You might however consider implementing some sort of opt-in offline service, where the latest gps position is stored on a server including a timestamp. When somebody else (with the app running) moves within a certain distance of this location while it's still "fresh", then you send off a notification to the first device. That way the user would be notified that somebody may be close, and can then switch on their own device.