The document discusses the application lifecycle on mobile devices and how developers should handle interruptions, user expectations, and different lifecycle events. It covers topics like tombstoning, where the application is dead but some state is saved, and how restoring state is important for a good user experience. Code samples demonstrate saving state on deactivation and restoring it on activation. Managing resources properly during lifecycle events is required for apps to be published.

1. Application Lifecycle Jason Lee Ethos Technologies

3. Application Lifecycle

4. Tombstoning

5. Lifecycle Events

6. Resource Management

7. Play Time

9. A user action (i.e. press the start button)

10. An external event (an incoming phone call)

11. An internal action (i.e. taking a photo, choosing a contact)

12. Interruption characteristics

13. Interruptions are not predictable

15. Phone is resource-constrained device, therefore we need to consume resources carefully

16. Phone is different from Desktop OS, which can hold multiple windows running processes simultaneously

17. However…

18. A user expects the application to be able to remain in the state where it was left

21. The app is dead

22. Some relevant data is saved by System for the app/page, which is called State information

23. When user navigates back

24. System restarts the application, passes applications state back to the App

25. System navigates to the very page where it was left, passes page state back to the Page

26. Developers should

27. Write code to save state before the app gets tombstoned

29. Fired when the application is started

30. Not fired when the application is reactivated

31. Load app settings/configuration

32. Application_Activated

33. Fired when the application is reactivated (brought to foreground)

34. Not fired when the application is started

35. Restore app state if tombstoned

36. Application_Deactivated

37. Fired when the application is deactivated (sent to background)

38. Not fired when the application is closed

39. Save app state as needed

40. Application_Closing

41. Fired when the application is closing (i.e. user presses Back key)

42. Not fired when the application is deactivated

44. Fired when the application is started

45. Not fired when the application is reactivated

46. Restore page state if tombstoned

47. OnNavigatedFrom

48. Fired when the application is deactivated (sent to background)

49. Not fired when the application is deactivated

52. You have only 10 seconds to finish all job

56. Resource Management - 1 Deactivating App Page. OnNavigatedFrom - You may release phone resources, but not necessarily, the framework is doing it anyway - You MUST Save app/page state App. Deactivated Framework: Detach Resources Framework: Suspend Timers and Threads Dormant App

58. Socket : Reconnect

59. Camera: Recreate Object

60. Restore app state if tombstonedApp. Activated Framework: Attach Resources Framework: Resume Timers and Threads Dormant App

62. Microsoft tries its best to keep apps in the line, providing consistent user experience to end users.

63. It is about money !

65. To understand various lifecycle events and orders of occurring under different situations

66. To be able to store and retrieve state information