Crash-course for C# developers on getting started with C#/iOS development.

1. iOS for C# Developers
Miguel de Icaza – Xamarin Inc
@migueldeicaza

2. iOS Adoption

3. .NET Event Idiom
Objects raising a number
of events
MyControl
F.Clicked += EventHandler
OnEnter
OnLeave
Storage for
properties/events:
• either in object
• Or uses bags, like
DependencyProperties
Clicked
Background
Font

4. Objective-C Delegate Idiom
Objects use a peer object
to post notifications
MyControl
Delegate
Background
f.Delegate = new myDelegate ();
Must implement methods
in MyDelegate
Font
MyControlDelegate
OnEnter
OnLeave
Clicked

5. Objective-C Action/Target
• Poor man’s C# delegate.
• In .NET this is mapped to a C# delegate
– Use methods
– Anonymous methods
– Lambdas

6. C# on iOS
• All the features you come to expect from C#
• IDEs:
– Visual Studio on Windows
– Xamarin Studio on Mac
• Think of iOS as another platform to target
– Just like you ASP.NET or WPF are
– Same level of code sharing

7. APIs for C# Developers on iOS
• .NET’s Base Class Libraries
– mscorlib, System, System.Core, System.Data
– System.Web.Services
– etc
• Native iOS APIs surfaced as C# classes
– Mapped with some artistic liberties:
– Follow .NET’s Framework Design Guidelines

8. iOS APIs Surfaced to .NET
• Objective-C to C# bridge
– Special runtime support for these
– Integrates the Object Systems
• Object Oriented C Code
– Manually mapped to C# classes
• Mostly CoreFoundation derived types
• Regular C code
– Mapped to C# classes as well

9. iOS APIs for .NET
• iOS APIs are weakly typed
– Similar to .NET 1.0 code
• C# bindings are strongly typed
– Helps explore the API
– Let the IDE help you write your code
• Async-ified (same rules as .NET async)

10. THE BASICS

11. Starting Up
• C# Main () method
– Call UIApplication.Main
– Pass the name of your application delegate class
• System creates UIApplication class
– Instantiates your UIApplicationDelegate
• UIApplicationDelegate methods invoked
– FinishedLaunching performs UI setup

12. Complete app

13. UIApplicationDelegate
• How the operating system talks to your app
• Mostly deals with state:
–
–
–
–
–
Starting up (fresh, openUrl request)
Suspending
Resuming
Respond to notifications
Background downloads
• Also: data security, UI orientation

14. Hierarchy
Screens
Windows
ViewControllers
Views or ViewControllers

15. UIScreen
• Represents a screen available in your device
• UIScreen.MainScreen is the main screen
– Same as UIScreen.Screens [0]
• Other screens used for external connectors

16. UIWindows
• Developers use one (system does others)
– Routes events
– Sets the Root View Controller
• UIWindow.RootViewController
– Must be set by the end of running your
FinishedLaunching method.

17. UIView
• Base class for all UI
Elements
BackgroundColor = UIColor.Red

18. UIView Subclasses
UIButton
Simple UIViews
UIPicker
Controls
UISlider
UIControl
UISwitch
UIImageView
UIStepper
UILabel
UIView
UITextField
UIProgressView
UITableView
UIScrollView
UITextView
UICollectionView
10,000 foot view, not comprehensive
ScrollViews

19. UIViews are General Containers
Can be arbitrarily nested
UIView methods:
AddSubview (UISubview)
RemoveFromSuperview ()
Unlike Gtk/Winforms:
Everything is a container

20. Can be Arbitrarily Nested

21. UIView’s
• Frame
– Superview coordinates
– RectangleF
• Bounds
– Size in UIView’s
coordinates
• Transform
– 2D Affine transformation
• Center
– Superview coordinates
X, Y = (20,10)
Center X, Y = (35,20)
W,H=(50,30)

22. 2D Affine Transforms
Rotation
Translation
Shearing
Scaling

23. UIView’s
• Frame
– Superview coordinates
– RectangleF
• Bounds
– Size in UIView’s
coordinates
• Transform
– 2D Affine transformation
• Center
– Superview coordinates
45’ rotation over the
center

24. UIView Center+Affine Transforms
• Frame
– Superview coordinates
– RectangleF
• Bounds
– Size in UIView’s
coordinates
• Transform
– 2D Affine transformation
• Center
– Superview coordinates

25. Custom UIView - Rendering
• Override Draw (RectangleF region) method
– Must paint the entire requested region
• Obtain the UIGraphics’ current draw context
• CGContext: Immediate graphics API
– Similar to System.Drawing on Windows.Forms
– Not retained, like Silverlight

26. Sample
public override void Draw (RectangleF rect)
{
using (CGContext context = UIGraphics.GetCurrentContext ()) {
// turn on anti-aliasing
context.SetAllowsAntialiasing (true);
// loop through each spot and draw it
foreach (Spot s in touchSpots) {
context.SetFillColor (s.Red, s.Green, s.Blue, s.Alpha);
context.FillEllipseInRect (new RectangleF (s.Point,size));
}
}
}

27. Custom UIViews – Touch Handling
• Configure properties:
– UserInteractionEnabled, MultipleTouchEnabled
• Override:
TouchesBegan:
– User touched the UI
TouchesMoved
– Updated locations
TouchesEnded
– User lifted fingers
TouchesCancelled
– System cancelled (for example, incoming call)

28. Animation
• UIKit is powered by an animation framework
– Details, beyond the scope of today’s talk
• Certain properties can be animated:
– Frame, Bounds, Center, Transform
– Alpha, BackgroundColor, ContentStretch
• Very little setup needed

29. Animation + Async
• UIView.Animate methods
• Use AnimateNotifyAsync family of methods
– Duration
– Lambda to update visual properties
– Options controlling animation
• Await on the call
– Will resume execution after animation completes

30. Sample

31. Dynamics – new in iOS 7
• Introduces a physics engine into the UI
– Gravity
– Collision
– Attachment
– Snap
– Forces/Pushing

32. Gravity + Collision Detection

33. UIViewController
• Typically a full screen of content
• Host for your views
– In charge of layout
– Orientation changes
– Provides event routing for your views
• Some can host other UIViewControllers
– “UIViewController Containment”
• UIViewController.View property is the root UIView

34. Manually Creating your UI

35. Using a UI Designer

36. UIViewControllers in UIKit
UIActivityViewController
Built-in UI
UICollectionViewController
Building Blocks
UINavigationViewController
UIPageViewController
UIViewController
UIReferenceLibraryViewController
UITabBarViewController
UITableViewController
UISplitVuewController
UIViewControllers in UIKit.

37. Built-in UI
UIActivityViewController
UIReferenceLibraryViewController

38. Other UIViewControllers
•
AddressBookUI
•
– ABNewPersonViewController
– ABPersonViewController
– ABUnknownPersonViewController
•
– MCBrowserViewController
– MCPeerPickerViewController
•
EventKitUI
– EKCalendarChooser
– EKEventViewController
MultipeerConnectivity
PassKit
– PKAddPassesViewController
•
QuickLook
– QLPreviewController
•
GLKit
– GLKViewController
•
•
Social/Twitter
– SLComposeViewController
– TWTweetComposeViewController
GameKit
– GKMatchmakerViewController
•
•
MediaPlayer
– MPMediaPickerController
– MPMoviePlayerViewController.
StoreKit
– SKStoreProductViewController

39. Some Examples
ABNewPersonViewController
EKEventViewController

40. Some Examples
TWTweetComposeViewController
MPMoviewPlayerViewController

41. UIViewControllers and Storyboards
• Name your class in the designer
– Will be reflected in your code
• Only after ViewDidLoad () are objects created
– Any references to other views or controllers
– Wont be valid until after this method is called

42. Presenting View Controllers
• Given a current UIViewController, call:
– PresentViewController
– PresentViewControllerAsync
• Modality of controller:
– bool ModalViewController {get;set}
• You can build your own visual transition
– And control every step of it

43. UIControl

44. Common Controls

45. Strongly Typed Notifications
• NSNotificationCenter
– Application Message Bus
– Hub for posting messages
• “Keyboard will appear”
• “Font size changed”
• Strongly typed in C#
– Class.Notification.ObserveXXXX ()

46. Strongly Typed

47. THREE VIEWS TO MASTER

48. UIScrollView
• Where the magic originates
• Powerful control that handles scrolling
– Pagination, scrolling, smooth motion
• Must see: Series of WWDC talks on it
– Every possible trick and hack

49. UITableView
• Most UI in iOS is a table
• Variable height
• External Data Source
– Request Section/Row
– Return UITableViewCell
• External Delegate
• Powerful
• And Cumbersome

50. MonoTouch.Dialog – UITableView
made easy
• Switches the model
– From callback to fetch data (very scalable)
– To dump all data into view (easy, not scalable)
• Elements:
– Provide cell-specific style renderers

51. MonoTouch.Dialog sample
• Sample program
• Mimics Sounds Settings

53. UICollectionView
• Arbitrary collections
• In any form you want
–
–
–
–
Table, Grid
Baseball diamond
Circle
Or anything you can
provide rules for

54. More Resources
Wallace McClure’s talk
Mechanics of it - Right after this one
Islander IE
• http://developer.apple.com/ios
•
Apple’s site
• http://docs.xamarin.com/ios
– Docs, tutorials on C# and iOS
• http://planet.xamarin.com
– Technical Blogs from the community