I have created the application, which track the GPS Location of user at specific time period. This process is run 3 times in background. So, App need to keep alive in background.
To achieve the our requirement, we use the Location manager (GPS) running in the background. So, it will never been killed by OS. Also, we have run the background task thread while App is in background.
This approach working fine on iOS 6 and before and running more than 10 minute in background.
But in iOS 7 Application going to killed after 10 minute.
Please need suggestion for keep the Timer alive in background.
We would appreciate the earliest response. Thank you in advance.
How to keep app running alive in background in IOS 7 without affecting the battery life.
There's no reason for the app to be killed if it has background location tracking functionality in the Info.plist file and doesn't try to abuse the benefits of that permission.
I'm not sure what's your use case for the tracking functionality, but -- together with an assumption that if there's no record from some period, the tracked device didn't change the location -- setting a distance filter would allow to track the location all the time.
That also allows to put a smaller burden on device's battery, because in certain activity types handled by CLLocationManager, the device may put the location service in idle state if it doesn't detect any significant movement.
if you want to keep app active in background and don't want to go to appstore for some reason (for example you are developing something for your company with using enterprise developer program), you should check deferredLocationUpdates(even on devices which doesn't support them, you just get error in your delegate but app will work) and don't call stopLocationUpdates while in background.(if you use this on app for appstore you have to explain why you needed this to apple of course).
Related
There are different ways to run tasks in the background in Android and iOS respectively. I have found What is the best way to schedule task in android? as well on stack overflow.
I am wondering which is the best way using react-native only. Would it be good enough to use setInterval or setTimeout for tasks that have to run daily or every few hours?
Would not those tasks be killed by the OS?
Any ideas or suggestions?
I will answer my own question to see if this information can be of used by anyone looking for it.
Since the different mobile OSs tend to kill background jobs, or stall them to save battery, there are few deterministic methods to schedule tasks in react native. I use a combination of the following:
Offload timers to the background, which work with the app in both fore and background https://github.com/ocetnik/react-native-background-timer (!If you use create-react-native-app you must eject it)
Use a background-fetch for iOS and HeadlessTask in Android, here is a decent library https://github.com/jamesisaac/react-native-background-task
Use geolocation updates to wake up the app and start threads https://github.com/mauron85/react-native-background-geolocation.
I guess you can follow similar strategies using bluetooth wake-ups.
Push notifications from a server to ensure deterministically that the app wakes app (except it having been killed by the OS). In iOS, ensure that you call notification.finish() to avoid being discriminated by the task handler algorithm.
For Android you can try to use AlarmManager API https://github.com/vikeri/react-native-background-job.
Beware of the dragons: your app might be closed if it abuses execution time or memory usage after a system wake up. You may have to rehydrate all listeners after the phone was left without battery. So the user still needs to interact heavily with your app.
Update:
From Android O there are very strict background execution limits. When using a HeadlessJSTask service, ensure that it is launched as a foreground service if you want it to last longer than a few seconds. It may require a notification with it. Take into account that only loading the bundle can take up to a few seconds, depending on your app and the device.
As a matter of fact there is not any sufficient way for that. but we can remark mauron85 as a way which is better then others on android but also it doesn't work perfectly on IOS. for example if app has killed by user the job would not keep working or there is not any control of job execution quantity the job fires each time device changes its position.
other components like react-native-background-fetch and react-native-background-task have the limitation of job execution period(the job repeats after each 15 minutes and there is no way to decrease this time period) and they just work on android.
it would be great if Facebook react native has some practical solution for this problem.
I am testing our iBeacons on iOS 7.1 and I can detect beacons correctly when I am in foreground and invoke the app from the background. However the issue comes when user has killed the app. The "didDetermineState" callback get invoked twice when I am in the beacon region while the app is killed. Am I missing the obvious or has anyone experience this same behavior ?
I have seen this happen not just when the app is completely killed, but in other cases, too. You will need to add filtering logic to your region callback methods, so if you get multiple calls it doesn't cause trouble in your app.
Another common issue is that you will get an exit region notification, followed within a couple of seconds by an entry region notification. Again a software filter is the way to deal with this. An example of a software filter for iBeacon callbacks is described here.
When developing an app that uses Bluetooth Low Energy, there comes a time when the iOS device loses connection to the peripheral. (Sometimes for hours.)
In order to reconnect to an existing peripheral, the app must constantly scan in the background at a specific rate throughout the day(s), even when the app is backgrounded.
The problem is, iOS will not guarantee that your app will not get killed, due to memory constraints, etc.
Information found in the iPhone OS Programming guide states that:
Apps that work with Bluetooth peripherals can ask to be woken up if
the peripheral delivers an update when the app is suspended. This
support is important for Bluetooth-le accessories that deliver data at
regular intervals, such as a Bluetooth heart rate belt. When an app
includes the UIBackgroundModes key with the bluetooth-central value in
its Info.plist file, the Core Bluetooth framework keeps open any
active sessions for the corresponding peripheral. In addition, new
data arriving from the peripheral causes the system to wake up the app
so that it can process the data. The system also wakes up the app to
process accessory connection and disconnection notifications.
The problem does not arise when the phone is connected to a device and the application is background. It does happen, however, when the device is disconnected and the app is backgrounded. In this specific case, the phone is no longer connected to the peripheral, and therefore no longer getting notifications.
Many people have discussed this before, either on Stack Overflow or the Apple forums, and I believe one of the Apple developers has responded saying:
We're aware of this issue and are trying to come up with a solution.
Currently, there is no workaround."
My question is, is there a way to at least improve your chances of not getting killed by iOS due to memory constraints?
For example, an instant messaging app (IMO) seems to run quite nicely in the background. After days and days of not being used, the app will wake up and display a gChat message.
I’m questioning things such as
Strong pointers
Overall memory size
Reducing memory size when app is backgrounded or minimized
Reducing frequency of background operation
Etc.
Why do you need background execution even when the bluetooth hardware is disconnected?
I don't think that you need to "rescan continuously" to reconnect again, if the hardware is "paired" with the iPhone/iPad, it will reconnect itself. Like a bluetooth headset. Or not?
AFAIK you have no chances to accomplish what you are asking for.
A normal App is always suspended when the user go back to home. The app has approx. 5 secs of background time to stop timers, save state ecc ecc.
There are special background modes that allows you to have more background time, and each of this mode (explained in the page you linked) has a different behavior.
About the bluetooth mode:
The descripted behavior is not an issue, but it's by design:
the app is suspended
when the app is suspended, it can be killed by the OS to free ram (and there are no tricks to avoid this), but the system will wake up if needed.
the app is then awaken every time a notification is received (awaken from suspended state or lauched from "previously-killed" state)
the app has 10 seconds to do tasks (save informations, ecc ecc). Moreover, can request +10 mins. of background time for a particular task
after the 10 secs (or 10 min) the app is suspended again
The example you wrote about the chat app is incorrect: chat apps usually doesn't use any background mode, simply they forward you messages using push notifications. When you open the app, the app connect to a server that stores all your messages and download it.
You can get "more uptime" using location background mode (routing app can work in background), or using a combination of significative location changes (the app is awaken) and the 10 minutes background time, but I think that Apple will reject an app that "abuse" this.
Shortly, you have to design your app to support this behavior.
I found this in some more Apple documentation:
Memory Usage for Background Apps
Every app should free up as much memory as is practical upon entering
the background. The system tries to keep as many apps in memory at the
same time as it can, but when memory runs low it terminates suspended
apps to reclaim that memory. Apps that consume large amounts of memory
while in the background are the first apps to be terminated.
Practically speaking, your app should remove strong references to
objects as soon as they are no longer needed. Removing strong
references gives the compiler the ability to release the objects right
away so that the corresponding memory can be reclaimed. However, if
you want to cache some objects to improve performance, you can wait
until the app transitions to the background before removing references
to them.
Some examples of objects that you should remove strong references to
as soon as possible include:
Image objects
Large media or data files that you can load again from disk Any other
objects that your app does not need and can recreate easily later To
help reduce your app’s memory footprint, the system automatically
purges some data allocated on behalf of your app when your app moves
to the background.
The system purges the backing store for all Core Animation layers.
This effort does not remove your app’s layer objects from memory, nor
does it change the current layer properties. It simply prevents the
contents of those layers from appearing onscreen, which given that the
app is in the background should not happen anyway. It removes any
system references to cached images. (If your app does not have a
strong reference to the images, they are subsequently removed from
memory.) It removes strong references to some other system-managed
data caches.
From the apple documentation i have always assumed the following:
connectPeripheral:options:
Establish a connection to the peripheral.
- (void)connectPeripheral:(CBPeripheral *)peripheral options:(NSDictionary *)options;
Parameters
peripheral
The peripheral to connect to.
options
A dictionary to customize the behavior of the connection. See CBConnectPeripheralOptionNotifyOnDisconnectionKey.
Discussion
**This never times out**. Use cancelPeripheralConnection: to cancel a pending connection.'
With the important part being on the fact that this never times out. I would assume this would hand off to the system so that it will connect automatically to the peripheral when it comes into range, thus removing the need for full backgrounding. Someone correct me if im wrong though!
I have created a web-service app and i want to populate my view controllers according to the response i fetch(via GET) in main thread. But i want to create a scheduled timer which will go and control my server, if there becomes any difference(let's say if the count of an array has changed) i will create a local notification. As far as i read from here and some google results, i cant run my app in background more then ten minutes expect from some special situations(Audio, Vo-IP, GPS).. But i need to control the server at least one per minute.. Can anyone offer some idea-or link please?
EDIT
I will not sell the app in store, just for a local area network. Let's say, from the server i will send some text messages to the users and if a new message comes, the count of messages array will increment, in this situation i will create a notification. I need to keep this 'controlling' routing alive forever, whether in foreground or background. Does GCD give such a solution do anyone have any idea?
Just simply play a mute audio file in loop in the background, OR, ping the user's location in the background. Yes, that will drain the battery a bit, but it's a simple hack for in-home applications. Just remember to enable the background types in your Info.plist!
Note: "[...] I fetch (via GET) in main thread." This is not a good approach. You should never fetch any network resources on the main thread. Why? Because your GUI, which is maintained by the main thread, will become unresponsive whenever a fetch isn't instantaneous. Any lag spike on the network results in a less than desirable user experience.
Answer: Aside from the listed special situations, you can't run background apps. The way I see it:
Don't put the app in the background. (crappy solution)
Try putting another "entity" between the app and the "server". I don't know why you "need to control the server at least one per minute" but perhaps you can delegate this "control" to another process outside the device?
.
iOS app -> some form of proxy server -> server which requires
"babysitting" every minute.
I started off on the Win8 metro app (javascript) development recently. For notifications, it is clear how the WNS notifications will be useful for creating live tiles.
However the use case for local notifications is not clear to me. I have these two questions:
is it correct to assume local notifications make sense only for apps that would run in the background e.g. when other apps are running or when the system is locked?
if the above is not true, then kindly suggest some examples of when local notifications will be useful.
regards
CGere
Local notifications are useful to update your tile on the start screen that persist after your app was closed/suspended. For example you might want to update the tile when your app closes with some context, perhaps an image from the last level of the game they were on or such.
When your app goes to the background it has a short period of time to suspend after which your app will no longer be running and thus unable o update the tile. You can however create a background task to run on an event/timer to do some work (such as update your tile).