With mobile taking off in a big way it is a fun and exciting time to be a software developer. The landscape is rapidly changing, with a wide variety of options for platforms and programming languages. Businesses are faced with tough decisions on how to provide a best possible user experience, yet keeping maintenance cost down across the different smart phone platforms. Some are compromising user experience and betting on web based interfaces, while others require the high fidelity user experience or device integration traditionally only found in native apps. In this session I will demonstrate how we can write fully native applications taking full advantage of the platform, yet achieving a high level of code reuse across Windows Phone 7, Android and iOS. Topics covered: - Separated Presentation patterns for maximum code reuse across all platforms - How to structure your source code and build it for all platforms - How to access devices specific functionality like Camera, GPS and Accelerometer in a cross platform way - Tips, tricks and tools to make the cross platform development process smoother. For maximum benefit from this session some prior knowledge of MVVM is beneficial.

1. Cross platform mobile apps using .NET Jonas Follesø NDC, June 2011

3. 8 techniques

4. Complete examplehttp://www.flickr.com/photos/20792787@N00/2248623391/

7. TILE FLOOD

8. TILE FLOOD

10. Why cross platform..?

11. REUSE SKILL SET?

12. REUSE CODE? privatevoidopen_Click(objectsender, RoutedEventArgse) { varchannel=HttpNotificationChannel.Find("NNUG"); if (channel==null) { channel=newHttpNotificationChannel("NNUG"); } channel.ChannelUriUpdated+=channel_ChannelUriUpdated; channel.ShellToastNotificationReceived+= channel_ShellToastNotificationReceived; channel.Open(); }

14. LIKE C#..?

15. ... OR DISLIKE THE ALTERNATIVE

16. OBJECTIVE-C: DATE (NO TIME) + (NSDate *) stripTime:(NSDate *) date {NSCalendar *gregorian = [[NSCalendaralloc] initWithCalendarIdentifier:NSGregorianCalendar];NSDateComponents *components = [gregorian components: (NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:date]; date = [gregoriandateFromComponents:components]; [gregorian release]; return date;}

17. C#: DATE (NO TIME) public DateTimeStripTime(DateTime date){ return date.Date;}

19. TECHNIQUE 1:PORTABLE CLASS LIBRARY

20. HELP YOU STICK TO A COMMON SUBSET

23. No Platform Specific Code in Class Lib

25. WORKS IN MONODEVELOP

27. Ability to add platform specific code

33. using System.Net; #if MONOTOUCH || MONODROID using System.Web; #endif

36. TECHNIQUE 6:ABSTRACT COMMONFUNCTIONALITY

37. publicinterfaceIDispatchOnUIThread { void Invoke(Action action); }

38. // Windows Phone 7 publicclassDispatchAdapter : IDispatchOnUIThread { publicvoid Invoke(Action action) { Deployment.Current.Dispatcher.BeginInvoke(action); } }

39. // Mono for Android publicclassDispatchAdapter : IDispatchOnUIThread { privatereadonlyActivity _owner; public DispatchAdapter(Activity owner) { _owner = owner; } publicvoid Invoke(Action action) { _owner.RunOnUiThread(action); } }

40. // Monotouch publicclassDispatchAdapter : IDispatchOnUIThread { privatereadonly NSObject _owner; publicDispatchAdapter(NSObject owner) { _owner = owner; } publicvoid Invoke (Action action) { _owner.BeginInvokeOnMainThread(newNSAction(action)); } }

43. Ensure that any code that manipulates presentation only manipulates presentation, pushing all domain and data source logic into clearly separated areas of the program. Martin Fowler, Separated Presentation, July 2006

45. Separated Presentation Patterns

46. Data & Domain Logic(Model) UI(View) Interaction (Controller/Presenter)

47. MVVMPATTERN FOR BINDABLE UI

48. APP LOGIC IN CODE BEHIND IS HARD TO TEST AND MAINTAIN VIEW XAML DataModel Code-Behind EventHandlers

49. SEPARATE USINGMVVM VIEW XAML Code-Behind Change notification Data-binding and commands VIEW MODEL Data Model State + Operations

50. publicclassObservableAdapter<T> : BaseAdapter<T> { privatereadonlyActivity _context; privatereadonlyObservableCollection<T> _collection; publicObservableAdapter(Activitycontext, ObservableCollection<T> collection) { _context = context; _collection = collection; _collection.CollectionChanged += (o, e) => NotifyDataSetChanged(); } ... ListAdapter = newObservableAdapter<Airport> (this, _viewModel.Airports);

51. publicabstractclassObservableDataSource<T> : UITableViewDataSource { publicObservableDataSource (ObservableCollection<T> collection, UITableView tableView) { _tableView = tableView; _collection = collection; _collection.CollectionChanged += (o, e) => { tableView.ReloadData(); }; } ...

55. TECHNIQUE 8:USE PRE-BUILT ABSTRACTIONS

56. PHONE SPECIFIC APIS? http://www.flickr.com/photos/howzey/2880455762/

58. Camera

59. Compass

60. Geolocation

61. Notification

62. Storage

63. Contacts

65. One common API for phone specific functionality across all three devices

66. Inspired by PhoneGap(same API)http://www.flickr.com/photos/tambako/3974809361/

67. privatevoid FindNearestAirport() { var coordinates = new MonoMobile.Extensions.Geolocation(); coordinates.GetCurrentPosition(PositionAvailable); } privatevoid PositionAvailable(Position position) { Console.WriteLine("{0} {1}", position.Coords.Latitude, position.Coords.Longitude); }

68. privatevoid FindNearestAirport() { var coordinates = newMonoMobile.Extensions.Geolocation(); coordinates.GetCurrentPosition(PositionAvailable); } privatevoid PositionAvailable(Position position) { Console.WriteLine("{0} {1}", position.Coords.Latitude, position.Coords.Longitude); }

70. Implemented using LocationManager

71. MonoTouch -> MonoMobile.Extensions.dll

72. Implemented using CLLocationManager

73. Windows Phone 7 -> MonoMobile.Extensions.dll

75. Same set of abstractions used in multiple apps

78. FLIGHTS NORWAYMONITORARRIVALS AND DEPARTURES http://www.flickr.com/photos/svenwerk/2181849280/

80. demo

81. SUMMARY Portable Library Linked Files Project Linker VSMonoTouch Preprocessor Directives Abstracting Common Functionality Leverage MVVM Using Pre-built Abstractions