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`Android vs. iOS Development:  
`Background Processing 
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`Published on June 27, 2016 
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`Matthew Casey  Follow 
`Head of Artificial Intelligence and Machine Learning at D‐CAT Digital Content Analysis 
`Technology Ltd 
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`If you are building an app which needs to access resources when the user is not actively
`using the app, then you will need to do some kind of background processing. A popular
`example at the moment might be a health app which measures motion in order to track
`your activity. This all sounds very simple, but the reality is that mobile development can
`get quite complex once you want to start doing this sort of thing. We look at what is
`possible on Android and iOS.
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`Why Background Processing? 
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`There is one key question you should always ask if you are thinking about doing
`background processing in an app: "why?" As developers, we can probably think of lots
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`https://www.linkedin.com/pulse/android-vs-ios-development-background-processing-matthew-casey/
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`ironSource Exhibit 1011
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`of compelling reasons why we want to do things in the background. Maybe, for
`example, there is some maintenance processing we would like to do. More
`appropriately, we may want to access the device’s sensors to record activity or location
`— the most likely scenario for a health app.
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`The reason for asking "why?" is to make sure that there really is a compelling reason to
`do background processing. Having a compelling reason means that the user is more
`likely to allow that processing to take place. For example, if you are building a game,
`why would the game want to run in the background when the user is not playing it?
`Everything that runs in the background will use up battery and processing time and
`games certainly do not get played in the background. If the user works out that your app
`is running when it does not need to, and perhaps consuming lots of battery in the
`process, then they are likely to force-quit the app or uninstall it. The operating system
`might also run out of memory, in which case it will silently kill your app.
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`This is also true if your app wants to access sensors on the device, such as to obtain
`location information, or to track motion. We may well allow a map app to know our
`location when we are using the app, but why would we want it to track our location
`when the app is closed and we are not using the map? Not only will we not give the app
`permission to access our location all the time, we are again likely to force-quit it.
`However, if the app is tracking your daily jog to record distance, plus working out how
`much exercise you had, then we are almost certain to allow background processing. Of
`course, there are limits — if the app consumes all your remaining battery charge then it
`is likely to be uninstalled.
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`Background Processing on Android 
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`Overall Android is a far more liberal platform to work with. On Android, with the
`correct permissions granted, you can pretty much do whatever you need. Background
`processing when the app is paused can be achieved using a service.
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`A service is simply a component of your app which runs without a user interface.
`Services can be configured as a processing queue — starting when needed and then
`shutting down — or as a standalone background processor. As a standard
`component, services have a context which allows them to access all of the shared
`resources for the app, as well as sensors. This means that your service could tick along
`in the background receiving location or motion updates, perhaps saving these to a
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`https://www.linkedin.com/pulse/android-vs-ios-development-background-processing-matthew-casey/
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`database. They do not have a user interface, but this just means that when your app is
`next opened by the user, your app can do whatever it needs to do with the data that has
`been recorded or processed to update the display.
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`What about when the Android device is re-booted, can you carry on background
`processing automatically? Yes. By registering a BroadcastReciever, which responds to
`the BOOT_COMPLETED intent, you can re-start your service whenever the device re-
`boots. The only thing you cannot do is stop the user killing your app, which will also
`kill the service. Once killed, the service will only re-start if you act on the re-boot
`broadcast, or if the user re-starts your app themselves.
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`All sounds relatively easy. The problem is perhaps that it is too easy to get carried away
`and do lots in the background. Remember though, if your app uses lots of battery
`power, or seems to be doing unnecessary things in the background when your app is not
`being used, then the user is likely to force-quit it or uninstall. Think carefully what you
`do in the background and make sure you do not eat battery charge.
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`Background Processing on iOS 
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`This is where things get tricky. Background processing in iOS is highly regulated, with
`only certain types of background processing allowed. This is also enforced in the Apple
`review of your app to make sure you are not trying to circumvent the rules by
`pretending to do one thing, while doing another.
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`Apple require you to present a compelling reason for doing background processing. One
`way to get some time to do some background processing is to request additional time
`when your app is being put into the background. By beginning a background task, iOS
`will give your app more time, but still expects this to be finite. Some apps do use this to
`get around background restrictions by essentially continually requesting more time.
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`Another, and more legitimate way, to get some long-running background processing
`time is to use an appropriate background mode. For example, getting the device’s
`location while in the background is a typical background requirement for, say,
`navigation or tracking apps. To do this you need to enable the appropriate background
`mode in Xcode, request the relevant "always" permission from the user, start location
`updates when in the foreground, then do something with the location in the background.
`This location background mode can also be used as a legitimate way of obtaining
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`accelerometer data, since the two normally go hand-in-hand for health apps.
`Nonetheless, to pass the Apple review, you also need to put "Continued use of GPS
`running in the background can dramatically decrease battery life" on the app’s iTunes
`listing.
`
`Following this to get background location updates will get you to the point of being able
`to do background processing. Of course, even this can be a little difficult to check as
`different iOS releases and the simulator can all behave differently when an app enters
`the background. For example, on a real device, your app will be suspended almost
`immediately after entering background mode without the correct configuration, whereas
`on the simulator, it will keep on running. Even with the correct configuration, you only
`have a limited time to complete your background processing for every location update.
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`The issue with background processing, and particularly with using sensors, is the drain
`on the battery. Here then, you will need to tune your app to only use the GPS sensor at
`infrequent intervals to maintain low battery usage. However, even this approach will not
`solve the problem of re-starting your app’s background mode when the device is re-
`booted. Normally and app is only re-started explicitly by the user. A way around this is
`to enable one of the various sensor update modes which will automatically re-start your
`app when an update is received. For location updates, this is via monitoring significant
`location updates, which will wake up your app, but at the expense of only when the
`device has moved a significant distance from its last known location (stated as at least
`500 meters and no more frequent than every 5 minutes). Apple recommend monitoring
`significant location updates for background processing since it dramatically reduces
`battery drain.
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`Background Processing Made Easy 
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`These two different approaches mean that while Android is fairly straightforward to
`deal with, iOS is not. Building an app which works for both platforms is therefore more
`problematic and you have to consider the implications in your design.
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`If you are dealing with locations (including GPS and beacons) or accelerometer
`updates, then we think we have a solution. The new Pervasive Location SDK provides a
`consistent interface to allow you to perform background processing to collect this
`sensor data without having to worry about how it all works.
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`https://www.linkedin.com/pulse/android-vs-ios-development-background-processing-matthew-casey/
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`Background sensor data collection in the SDK is being used in a new app being
`developed for Furnace Limited and the University of Surrey to support
`a BBC4 television programme about gravity which will be broadcast next year. The app
`will use background recording of accelerometer data to calculate how much our relative
`time slows down due to the effects of acceleration as per general relativity.
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`During November, the app will be used to find Britain’s best time traveller, with the
`winner announced in the programme. Look out for the app and measure just how much
`time travel you can do.
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`We can help 
`
`Digital processing is at the heart of innovation. It may be that you have a difficult or
`complex problem. Pervasive Intelligence have the expertise to cut through the
`complexity to give you a solution you can use in the real world.
`
`If you would like to know more, or are interested in what support we can provide, take a
`look at what we can offer and book a free consultation. To receive similar insight, just
`follow us on LinkedIn.
`
`https://www.linkedin.com/pulse/android-vs-ios-development-background-processing-matthew-casey/
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`Matthew Casey  Follow 
`Head of Artificial Intelligence and Machine Learning at D‐CAT Digital Content Analysis 
`Technology Ltd 
` 
`
`
`
`
`
`https://www.linkedin.com/pulse/android-vs-ios-development-background-processing-matthew-casey/
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