4 whats-new-in-ios7-m4-multitasking-slides

transcript

Jon Flanders@jon!anders

What’s new in iOS7Networking and Multi-tasking

Tuesday, September 3, 13

What you will learn...

§ All about the new options for multi-tasking and background execution

Background Tasks

§ Ever since iOS4, apps could request extra time to execute after being sent to the background

Background Tasks

§ Ever since iOS4, apps could request extra time to execute after being sent to the backgroundo 15 minutes of execution time

Background Tasks

§ This API remains in iOS7, but you may not need to use it (more on this later)

Background Tasks

§ If you do use it, the execution semantics have changed

Background Tasks

§ If you do use it, the execution semantics have changedo If user locked screen in iOS6, the background task would keep the phone awake

Background Tasks

§ If you do use it, the execution semantics have changedo If user locked screen in iOS6, the background task would keep the phone awakeo iOS7 puts the app to sleep; the app will get a time-slice once the phone wakes up

Background Tasks

§ If you do use it, the execution semantics have changedo If user locked screen in iOS6, the background task would keep the phone awakeo iOS7 puts the app to sleep; the app will get a time-slice once the phone wakes upo Execution time not guaranteed to be contiguous

New App Switcher

§ One of the major changes in the OS

New App Switcher

§ One of the major changes in the OS§ User can swipe up on app snapshot to kill the app

New App Switcher

§ One of the major changes in the OS§ User can swipe up on app snapshot to kill the app

o Unlike in iOS6, this also kills background execution

New APIs

§ Background Fetch

New APIs

§ Background Fetch§ Remote Noti!cations

New APIs

§ Background Fetch§ Remote Noti!cations§ Background Transfer Service

Background Fetch

§ When an app opens, typically it shows fresh data

Background Fetch

§ When an app opens, typically it shows fresh data§ When an app is brought to the foreground after being in the background,

generally the !rst thing most apps do is refresh their data

Background Fetch

generally the !rst thing most apps do is refresh their data o But update happens after the user is already in the app, so the user sees a transition

Background Fetch

§ Background Fetch enables an app to update its data in the background

Background Fetch

§ Background Fetch enables an app to update its data in the backgroundo If an app is in the background, it will be assigned a time-slice

Background Fetch

§ Background Fetch enables an app to update its data in the backgroundo If an app is in the background, it will be assigned a time-sliceo If an app isn’t running, it will be started in the background and then assigned a time-

Background Fetch

§ Background Fetch enables an app to update its data in the backgroundo If an app is in the background, it will be assigned a time-sliceo If an app isn’t running, it will be started in the background and then assigned a time-

slice o When and how often the app is assigned a time-slice is controlled by the OS

Background Fetch API

§ Set the UIBackgroundModes value in the Info.plist to “fetch”

§ Set the UIBackgroundModes value in the Info.plist to “fetch”o This can also be set this via the new Capabilities page in Xcode

§ Set the background fetch interval range on your Application object

§ Set the background fetch interval range on your Application objecto No repeating interval

§ Set the background fetch interval range on your Application objecto No repeating intervalo Time-slice assignment is managed by the OS, the range is set by the developer

§ New delegate callback

§ New delegate callbacko performFetchWithCompletionHandler

§ New delegate callbacko performFetchWithCompletionHandlero Do your work: call the completion handler when you are done

§ New delegate callbacko performFetchWithCompletionHandlero Do your work: call the completion handler when you are doneo After the completion handler is called, if you have new data, it will create a new

snapshot of your app

§ Update UI for App Switcher

§ Update UI for App Switcher§ You can test this via debug properties

o Also on Debug menu

Remote Noti!cations

§ Since iOS4, noti!cations could be sent through Apple’s Push Noti!cation Service (APNS)

Remote Noti!cations

§ Often sent to notify user of new data

Remote Noti!cations

§ Often sent to notify user of new datao User is noti!ed via alert or popup

Remote Noti!cations

§ Often sent to notify user of new datao User is noti!ed via alert or popup o If the user clicked on UI, the app was either brought to foreground or started

Remote Noti!cations

§ Often sent to notify user of new datao User is noti!ed via alert or popup o If the user clicked on UI, the app was either brought to foreground or startedo Race condition: what if app can’t show new data yet because new data can’t even

start to be retrieved until app is in the foreground

Remote Noti!cations

§ iOS7 enables you to send a noti!cation with a new "ag

Remote Noti!cations

§ iOS7 enables you to send a noti!cation with a new "ago content-available : 1

Remote Noti!cations

§ iOS7 enables you to send a noti!cation with a new "ago content-available : 1o When set, the app gets executed before the user gets the noti!cation

Remote Noti!cations

§ iOS7 enables you to send a noti!cation with a new "ago content-available : 1o When set, the app gets executed before the user gets the noti!cationo Hopefully you can get that new data before the user clicks the alert to bring the app

to the foreground

Remote Noti!cations

to the foreground

§ Send content-available:1 without an alert in the payload of the noti!cation

Remote Noti!cations

to the foreground

§ Send content-available:1 without an alert in the payload of the noti!cation o This becomes a silent noti!cation and is delivered to the app in the background

Remote Noti!cations API

§ Set UIBackgroundModes to remote-noti!cation in Info.plist

§ Set UIBackgroundModes to remote-noti!cation in Info.plist o Or use new Capabilities UI in Xcode

§ Make sure to set content-available: 1 in the payload

§ Make sure to set content-available: 1 in the payload§ The application:didReceiveRemoteNoti!cation:fetchCompletionHandler

is called with a non-null completion handler

is called with a non-null completion handlero Call the completion handler when you are done

is called with a non-null completion handlero Call the completion handler when you are doneo Silent noti!cations will be rate-limited. APNS does the work to make sure that device

isn’t overloaded – delayed but not rejected

Networking in the Background

§ Before iOS7, you might want to download or upload a resource after the your app has gone to the background

§ Background Task API would give you a set time-slice

§ Background Task API would give you a set time-sliceo What if your operation took longer than the time allowed (i.e. a large resource like a

video or image)?

Background Transfer Service (BTS)

§ iOS7 introduces the BTS

§ iOS7 introduces the BTS§ You can offload network work to the BTS

§ iOS7 introduces the BTS§ You can offload network work to the BTS§ BTS will ensure that the work gets completed

o Works even if your app is in the background or even if it is terminated

o Works even if your app is in the background or even if it is terminated o If your app wakes up due to background fetch or noti!cation, this is a great API to pair

with it

§ BTS manages battery life and data

with it

§ BTS manages battery life and data o Requests are classi!ed as discretionary or non-discretionary

with it

§ BTS manages battery life and data o Requests are classi!ed as discretionary or non-discretionaryo Discretionary requests will only happen when on WI-FI

with it

§ BTS manages battery life and data o Requests are classi!ed as discretionary or non-discretionaryo Discretionary requests will only happen when on WI-FIo Requests from the background are automatically discretionary

with it

§ BTS manages battery life and data o Requests are classi!ed as discretionary or non-discretionaryo Discretionary requests will only happen when on WI-FIo Requests from the background are automatically discretionaryo Requests from the foreground can request to be discretionary

NSURLSession

§ New object in iOS7

NSURLSession

§ New object in iOS7§ Subsumes the functionality of NSURLConnection

NSURLSession

o API is similar to NSURLConnection

NSURLSession

§ Adds more functionality than NSURLConnection

NSURLSession

§ Adds more functionality than NSURLConnectiono Instance storage of credentials, cookies, and other state (vs. NSURLConnection’s global

shared state).

NSURLSession

shared state).

§ If your app goes to the background or even is terminated after you make a NSURLSession request, BTS service will still complete the request

NSURLSession

shared state).

§ If your app goes to the background or even is terminated after you make a NSURLSession request, BTS service will still complete the requesto Your app is started or woken up when request is !nished and you have a chance to

process

NSURLSession API

§ To create an NSURLSession, you need an NSURLSessionCon!guration object

NSURLSession API

§ To create an NSURLSession, you need an NSURLSessionCon!guration objecto Con!guration object determines foreground/background execution, whether the

request will use only wi-!, etc.

NSURLSession API

request will use only wi-!, etc.o Background con!guration gets an identi!er (string) to use later to retrieve from BTS

NSURLSession API

§ Implement to appropriate protocols

NSURLSession API

§ Implement to appropriate protocolso NSURLSessionDelegate for high-level events

NSURLSession API

§ Implement to appropriate protocolso NSURLSessionDelegate for high-level eventso NSURLSessionTaskDelegate for data-level events

NSURLSession API

§ NSURLSessionTask really replaces NSURLConnection

NSURLSession API

§ NSURLSessionTask really replaces NSURLConnectiono [resume] method to start task

NSURLSession API

§ NSURLSessionTask really replaces NSURLConnectiono [resume] method to start tasko [cancel],[suspend],[resume] control methods

NSURLSession API

§ NSURLSessionTask really replaces NSURLConnectiono [resume] method to start tasko [cancel],[suspend],[resume] control methodso Multiple sub-classes for different functions

NSURLSession API

§ NSURLSession also has block-based convenience methods as well

NSURLSession API

§ NSURLSession also has block-based convenience methods as wello Still need to call [resume] on task to kick off connection

Background Considerations

§ Limited time

§ Limited timeo You still only get a limited time to execute in the background (less than 1 minute)

§ Limited timeo You still only get a limited time to execute in the background (less than 1 minute)o Make sure to call the completion handlers ALWAYS in less than 1 minute

§ Limited timeo You still only get a limited time to execute in the background (less than 1 minute)o Make sure to call the completion handlers ALWAYS in less than 1 minuteo Use BTS to enhance the work you can do when called in the background

§ User control

§ User controlo User can turn off or limit background fetch

§ Data Protection

§ Data Protectiono If you use the recommended levels of data protection, you won’t be able to access !les, keychain, or sqlite DBs when running in the background

o If you need credentials in the background, to lower risk, consider a token that expires in a short amount of time

Summary

§ The new background execution features help your app seem to the user to be running all the time

Summary

§ The new background execution features help your app seem to the user to be running all the time

§ The new NSURLSession and BTS make foreground networking code simpler and background networking code possible

4 whats-new-in-ios7-m4-multitasking-slides

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