I am working on a sports app that uses GPS and OpenEars text-to-speech. The app delivers speed and other GPS info to the user audibly (via earphones) so the user (skier, cyclist, etc) can get the GPS info without looking at the screen. In order to save battery life, I would like the app to run in the background with the screen off. Is this possible with IOS? I tried setting "Required backgrund modes" for both GPS and audio, but my app quits working when the screen is off.
thanks..
One one to get around it is to have a silent audio file playing, when there is no audio, it might get your app rejected in the app store though... here is a question that talks about the silent audio file playing to keep in the background... It might get through app store approval in your situation since it is an app that relays on audio as one of its main functionalities..
You can subscribe to GPS info change notifications and your app will run when something needs to be updated. Check this.
Please note this sentence:
"If you leave this service running and your application is subsequently suspended or terminated, the service automatically wakes up your application when new location data arrives. At wake-up time, your application is put into the background and given a small amount of time to process the location data. Because your application is in the background, it should do minimal work and avoid any tasks (such as querying the network) that might prevent it from returning before the allocated time expires. If it does not, your application may be terminated."
There's no way to do it as service except some special cases provided by ios. But you can simulate it. This post answer how to:
https://stackoverflow.com/a/19121250/2835520
I hope it's gonna help!
Related
I’m trying to make a focus timer app like Forest, that detects if you leave the app, either by going to the home screen, switching to another app or by first locking the phone and later proceeding to a different app through notifications, widgets, camera etc..
What I can’t figure out is how to monitor such state changes even after the phone has been locked for a while. There are no “background modes” covering this use case, so I would expect the app to get suspended after a while in the background. Nevertheless, apps like Forest do this successfully. Do I need a workaround to keep the app awake, or am I missing some approach that doesn’t require background execution at all?
Help much appreciated!
If I had to guess, it's probably a combination of a few things:
Use the normal app delegate callbacks for app state transitions to determine if the app is still able to execute code. That's the easy part.
You could do something with string and regex processing of console logs to detect when other apps open, close, etc. and other activity which would allow you to detect activity on the device coming from places other than your app.
You need to use some sort of framework that Apple says can get data even in background state. One such framework is Core Motion. There may be others as well that suit your app's specific needs better.
See Execution States for Apps.
See Background Execution.
See Cocoanetics: Accessing the iOS System Log.
See Keep iOS App Awake To Monitor Movement.
See Apple System Log Facility.
NOTE: This app I am working on is completely for my own usage and will not be on app store so please don't give answers referring that.
I want my app to do some process in background or after termination (double tap the home button and swipe the app from applications multitask) every few minutes. The process is very very light and quick so it won't drain the battery. This process shouldn't require internet connection. I have seen some answers here like and I will explain what are the problems:
VoIP. The problem with VoIP is wither it should be in background to use UIApplication.sharedApplication().setKeepAliveTimeout(..) method which doesn't work when the app is terminated or it should be connected to the internet to establish tcp connection and receive commands from sever and as mentioned before I want it to be internet independent.
Location Services. I found this excellent site with some great articles but the problem is it only works when the mobile phone is moved more than 500 meters. It depends on the location movement so when the phone is staying somewhere there will be no code execution.
Playing an silent audio loop. The problem here is if the user plays another audio (which is completely possible like music or phone call) the app will terminate!
Jailbreak Launch Daemons. I can't require jailbreak so it should be solved with a non-jailbreak solution:(.
I am free to use any kind of private-API's and there will be no restriction for that.
Thanks in advanced
I also faced with such problem, and don't find any solution.
The main problem is if user manually terminated app - in this case you can't do nothing...
Only way is:
a) use Location Services (as you mention)
b) use Push Notifications with background fetch
This question might be duplicate of many others but I am still asking because I really need to get any solution of it.
For iOS versions prior to 6, for devices other than those having an A7 chip.
I have an application which interacts with the Accelerometer. I am also running it in background by playing a sound file and turning the Audio services ON for background task.
Now If any third application plays music, it takes control of shared Audio Session of device which causes my background thread to call completion handler assuming that background task has been completed.
Now my application is interruptible by iOS and iOS can kill it if it remains in background for a long time after which I couldn't interact with accelerometer.
Is there any way/trick/hack to keep my application running all the time until unless I kill it by my own.
Again, this is a duplicate question but I really wanted to share my problem with you people to help me in this sense.
Apple is very clear on this:
Implementing Long-Running Background Tasks
For tasks that require more execution time to implement, you must
request specific permissions to run them in the background without
their being suspended. In iOS, only specific app types are allowed to
run in the background:
Apps that play audible content to the user while in the background,
such as a music player app
Apps that record audio content while in the background.
Apps that keep users informed of their location at all times, such as
a navigation app
Apps that support Voice over Internet Protocol (VoIP)
Apps that need to download and process new content regularly
Apps that receive regular updates from external accessories
Collecting accelerometer data is not listed. Therefore, what you are trying to do is not possible. "Ways, tricks, hacks" tend to get discovered quickly and offending apps removed from the App Store.
How does Navita https://itunes.apple.com/us/app/navita-t.e.m.-personal/id590228620?mt=8
manage to display a call log?
If I swipe the app out of the task manager then it misses the calls, this indicates that it must presumably be using CTCallCenter's callEventHandler and is creating its own call log by saving the time/duration in response to the callEventHandler callbacks.
However if that is the case then how does it manage to do this in the background? I was under the impression that callEventHandler can only be used by apps in the foreground and not in the background?
The app is using location services, however even after disabling this it was still able to get information about the calls (provided the app isn't suspended). I though it might be using background location updates to keep itself primed to receive callEventHandler callbacks but apparently not.
The Navita app is additionally able to display call time and call duration.
The bounty will be awarded to an answer which contains sufficient, accurate and detailed information that enables me to emulate the behavior of the Navita app, specifically I must be able to write an app that can obtain the time and duration of a phone call that occurred while the app was not in the foreground, while the device's location services was turned off, and after the app had been in the background longer than the ~3 minutes granted by using beginBackgroundTaskWithExpirationHandler:
Here is what I observe with the Navita app that I want to be able to reproduce:
1) Run app
2) Task away from app
3) Go to device settings, privacy, and turn off Location Services.
4) Go to device settings, privacy, background app refresh and turn off for the app
5) Wait > 10 minutes to make sure the app is not still in the background as a consequence of using beginBackgroundTaskWithExpirationHandler:
6) Call the device from another phone, answer the phone call, then hang up.
7) Launch the app again and display the call time and duration
(This is iOS7 and unjailbroken)
Here is what I've found from Navita TEM disassembly and it's resources.
Application uses two background modes - location and audio. You can see it in the Info.plist file. When you enable phone calls logging application will also enable "alerts" and "Real-time" switches. When "alerts" enabled application infinitely loops in background "bg-sound.mp3" file which has no sound, it's just silence. Because of that it doesn't use hacks like this one How to get a call event using CTCallCenter:setCallEventHandler: that occurred while the app was suspended? . It's similar trick to location used in order to keep the app running in background and receive phone call events. Somehow this was not rejected from the AppStore.
If you are observing the call center while the app is in the background you get a set of updates when the app is brought back to the foreground. This set of data may not be as accurate as if the app had been mostly in the foreground but it does include quite a bit of info.
I'm spec-ing an iOS app (which will be built outside of our company) which will upload a user's data entry to a server. If the device is not connected to the Internet, we'd like to save data on the device and upload it when the network is re-connected. (The app will primarily run on iPod Touch devices that will be disconnected most of the time).
If the user unlocks the device and re-opens our app after the network is reconnected, then uploading to the server should be easy because the app is running.
But what if the app is not running, where "not running" can mean one or more of:
device was power cycled
user has locked the device and it's sitting in his pocket
app crashed
user exited the app
user started using other apps so our app isn't running in the foreground anymore
are there other cases?
In the cases above, is there a way (ideally a battery-efficient way) to ensure that local data is uploaded soon after Internet connectivity is restored? Is the answer different depending on which of the cases above caused the app not to be running?
And is there a minimum iOS version the device will need in order to enable some (or all) of the above not-running cases to still upload when the app is not running?
My apologies if these are obvious newbie questions-- I'm not an iOS expert.
There is an interesting technique that is used by among others Instapaper and News.me(the pioneers of this technique) where you use region monitoring to initiate background downloads or uploads. Marco (Instapaper) blogged and talked (in episode 80 of the Build and Analyze podcast) about his communication with Apple so it should be a allowed in the App Store.
In brief the technique is that you set up certain regions (geofences) like "home" or "work" and respond to the locationManager:didEnterRegion: (and similar) callback(s). Your app will wake up from the background once you enter the pre-specified region and you can check to see if there is any data to upload.
This technique won't guarantee that the data is uploaded when the network reconnects but it will allow your app to automatically upload the information when the iPod Touch users gets home to their WiFi network.
That should most likely be at least once a day which may or may not be frequent enough for you. You could add a timestamp to when the initial upload was attempted and send that along the upload once it succeeds to get the correct order of events (data entries) on your server.
There is no way to ensure this. If your application is "not running" (by the definition described in your question), it will not be capable of responding to a change in the device's network status. It should be setup to resume upload operations the next time the application runs again.
EDIT:
Some of the cases you've described may indeed provide different opportunities for your application. Specifically, if the user "exits" the app by pressing the home button or launches another app in the foreground, your application may continue to run the in the background and could potentially respond to a change in network reachability.
The nature of what may be done in the background and for how-long is well documented, and supported by any version of iOS that supports multi-tasking. I recommend you review the documentation pertaining to App States and Background Services.
device was power cycled --> really NO WAY of resuming, unless you open the App!!!
user has locked the device and it's sitting in his pocket --> apps applicationStatus is UIApplicationStateInactive but it is running in the background. You still are able to react to notifications and i.e. accelerometer events. Try the Reachability Class and Log the changes!
app crashed --> NO WAY, unless opening the App
user exited the app --> App is sitting in the background. There you have a maximum of 10 Minutes Restriction of fully using your App (like the App "Pastebot" does)
user started using other apps so our app isn't running in the
foreground anymore --> Same as user exited the app
On multitasking Apple says the following:
Real multitasking only for certain kinds of usage, as there is Audio Background playing, VOIP (like Skype), navigation applications
All the other apps can request a specific amount of time after the app is closed/in the background, to finish certain tasks (as sending an email, sms or uploading/downloading important data)
Important Quote from dev docs:
Your app delegate’s applicationDidEnterBackground: method has approximately 5 seconds to finish any tasks and return. In practice, this method should return as quickly as possible. If the method does not return before time runs out, your app is killed and purged from memory. If you still need more time to perform tasks, call the beginBackgroundTaskWithExpirationHandler: method to request background execution time and then start any long-running tasks in a secondary thread. Regardless of whether you start any background tasks, the applicationDidEnterBackground: method must still exit within 5 seconds.
If you're building a restful API then I would recommend using RestKit, it has a request queue that checks the network status on the device and starts uploading once network access has been assured. You can read more about this here: http://mobile.tutsplus.com/tutorials/iphone/advanced-restkit-development_iphone-sdk/. Read the sections about Request Queue and background download/upload. It should be noted that RestKit is a big library which has it's advantages and disadvantages. I'm not completely sure how this que works with the app lifecycle, if it saves the request que even if the app is terminated. You would have to investigate that. RestKit does support background uploading/downloading, but as already noted, I think it's impossible to do any uploading if the app is terminated and not in background state.
I wouldn't recommend using RestKit if the API isn't Rest though.
You can download and experiment with RestKit here: https://github.com/RestKit/RestKit.