IOS multitasking is a lie, and that's totally fine.

iOS Multitasking is a lie.
And that’s totally fine.

Hi!
I’m James Jennings.
iPhone Developer
james@mobiledistortion.com
@jamesjennings

“Traditional” Multitasking
What is it?
Multiple programs sharing computer resources

“Traditional” Multitasking
So why are phones special?
Limited Resources
Processor
Battery

“New!” iOS 4 Multitasking
is a lie.
It’s not new
It’s not multitasking

Yeah, it’s not new.
iOS has always been “Unix-like”
Examples
Mail sending/receiving
iPod
App downloading
Oh and the phone

What is referred to as “Multitasking” in Apple’s agitprop is really just:
Fast Switching
Handful of OS hooks providing limited support for background execution of code

Who is worthy of iOS 4 & Multitasking?
Anybody with a jailbroken phone and a text editor

iOS 4 “Multitasking”
Fast Switching
Location Services
Audio
VoIP
Task Completion
Local Notification (kinda)

Fast Switching
The “Task Bar”
Apps aren’t directly terminated in iOS 4
“Freeze Dried” state information saved

Fast Switching
Apps can opt out
Apps can be kicked out
App is on Task Bar != App is eligible for fast switching

Location Tracking
3 Options
Normal AGPS
Significant Location Changes
Region Tracking (iPhone 4 only)
App developers must be aware of performance implications

Audio
Background audio, like native iPod
Access to player controls

VoIP
App can listen on network for incoming VoIP calls
Must use local notification to let user know

Task Completion
App can declare certain blocks of code as critical, which will continue to be executed even after app is terminated
Example in pre-iOS4
Mail
App can’t run itself indefinitely however, hard time limit enforced
App can declare cleanup code if it’s terminated

Local Notifications
Not really part of the “Multitasking” umbrella, available to all iOS 4 devices
Utilized by multitasking apps, however

Summary
“Multitasking” has always existed in the technical sense on the iPhone platform
The new multitasking in iOS 4 is a specific set of services and hooks
Some features are automatic, others must be implemented

Thank you!
Any questions?

IOS multitasking is a lie, and that's totally fine.

by James Jennings on Jan 24, 2011

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