iOS 9 introduced multitasking, which allows apps to be used side by side on certain devices. Along with this came a number of new APIs for handling transitions between different screen configurations. However, integrating these new APIs in an exiting codebase can be trick, and often requires rethinking the way a component is structured. This talk will introduce multitasking, cover the new APIs available to handle different scenarios, and walk through some gotchas when adding support for multitasking into existing applications.

1. Multitasking
The Hard Way
@micheletitolo
Lead Software Engineer, Capital One

2. What We’ll Cover
What are Multitasking and Adaptivity?
Creating Adaptivity
Tips, Tricks, and Gotchas

3. What Is Multitasking?

5. Adaptivity

8. Compact
Compact
Regular
Regular
✔
✔✔
x

9. Creating Adaptivity

10. • Launch.storyboard
• Full iPad rotation
• UITraitCollection
Mechanics

11. Apps Must Use A
Launch.Storyboard

12. Apps Must Allow
Full Rotation
Setting in Info.plist

13. UITraitCollection
horizontalSizeClass
verticalSizeClass

14. UITraitEnvironment
UIContentContainer

15. UITraitEnvironment
traitCollection
traitCollectionDidChange

16. UIView
UIViewController
UIPresentationController

17. UIContentContainer
viewWillTransitionToSize
willTransitionToTraitCollection

18. UIViewController
UIPresentationController

19. Different Use Cases

20. Responding To Changes

21. Multitasking Order

23. •applicationWillResignActive
•willTransitionToTraitCollection
•viewWillTransitionToSize
•traitCollectionDidChange
•applicationDidBecomeActive
Multitasking Order

25. •applicationWillResignActive
•willTransitionToTraitCollection
•viewWillTransitionToSize
•traitCollectionDidChange
•applicationDidBecomeActive
Multitasking Order

27. •applicationWillResignActive
•willTransitionToTraitCollection
•viewWillTransitionToSize
•traitCollectionDidChange
•applicationDidBecomeActive
Multitasking Order

28. Slideovers Are Still Inactive

30. Becoming Adaptive

31. Tools
Installed Views
Installed Constraints
Conditional Constraint Constants

32. Demo

38. Only Constraint Constants
Can Change

39. Tips, Tricks,
Gotchas

40. Autolayout

42. Rotation APIs

45. UISplitViewController

46. Compact == Modal

47. Still Can’t Be Pushed

48. Can Be Embedded

50. UIPopoverPresentationController

51. Also Fullscreen In Compact

52. UIPresentationController

53. Set modalPresentationStyle
To .Custom

54. adaptivePresentationStyleFor
TraitCollection:

55. UICollectionView

56. Don’t rely on
shouldInvalidateLayoutForBoundsChange

57. prepareLayout()
may have incorrect traits

58. use both
willTransitionToTraitCollection,
viewWillTransitionToSize

61. Bugs!

62. iPhone 2 NowiPhone 3.2 iOS 6
iPhone 5
iOS 9iOS 8
iPad iPhone 6/6+ iPad Pro
iOS 5 iOS 7

63. iPhone 2 NowiPhone 3.2 iOS 6
iPhone 5
iOS 9iOS 8
iPad iPhone 6/6+ iPad Pro
UIViewController
iOS 5 iOS 7

64. iPhone 2 NowiPhone 3.2 iOS 6
iPhone 5
iOS 9iOS 8
UISplitViewController
iPad iPhone 6/6+ iPad Pro
UIViewController
UIPopoverController
iOS 5 iOS 7

65. iPhone 2 NowiPhone 3.2 iOS 6
iPhone 5
iOS 9iOS 8
UISplitViewController
iPad iPhone 6/6+ iPad Pro
UIViewController
UIPopoverController
UIViewController Containment
iOS 5 iOS 7

66. iPhone 2 NowiPhone 3.2 iOS 6
iPhone 5
iOS 9iOS 8
UISplitViewController
Autolayout
iPad iPhone 6/6+ iPad Pro
UICollectionView
UIViewController
UIPopoverController
UIViewController Containment
iOS 5 iOS 7

67. iPhone 2 NowiPhone 3.2 iOS 6
iPhone 5
iOS 9iOS 8
UISplitViewController
Autolayout
iPad iPhone 6/6+ iPad Pro
UICollectionView
UIViewController
UIPopoverController UITraitCollection
UITraitEnvironment
UIViewController Containment
iOS 5 iOS 7

68. iPhone 2 NowiPhone 3.2 iOS 6
iPhone 5
iOS 9iOS 8
UISplitViewController
Autolayout
iPad iPhone 6/6+ iPad Pro
UICollectionView
UIViewController
UIPopoverController
UIContentContainer
UITraitCollection
UITraitEnvironment
UIViewController Containment
iOS 5 iOS 7

69. iPhone 2 NowiPhone 3.2 iOS 6
iPhone 5
iOS 9iOS 8
UISplitViewController
Autolayout
iPad iPhone 6/6+ iPad Pro
Multitasking
UICollectionView
UIViewController
UIPopoverController
UIStackView
UIContentContainer
UITraitCollection
UITraitEnvironment
UIViewController Containment
iOS 5 iOS 7

70. UITraitCollection Support
Has Been Added To
Older Components

71. Storyboards and Xibs

72. Frames Change When
Size Class Changes

75. First Time In A New Size Class
Adds Info To File

76. Misplaced Views In
Different Size Classes

77. Installed Views And Constraints Only
Work From Storyboards And Xibs

78. Conditional Constraint Constants Only
Work From Storyboards And Xibs

79. Any x Any

80. Constraints Must Be Set
For Any x Any
Even though no devices have that
size class configuration

82. Pick A Size Class To Use
For Any x Any

83. Interface Builder Warnings

84. UI Will Look Weird

85. Use Constraint Priorities

86. Questions?
https://github.com/mtitolo/space
https://github.com/mtitolo/primaries

87. Photo Credits
• https://unsplash.com/photos/iiaXf9xmgbM
• https://unsplash.com/photos/85hdWh8KtR4
• https://unsplash.com/photos/l5Tzv1alcps