2011-11-02 | 03:45 PM - 04:35 PM | Android Activities can possess one of four launch modes and one of many activity tasks. We will explore how your choices of launch modes and tasks affect your Applications back stack history and what will happen behind the scenes. After this talk you will confidently be able to wield the best launch modes for your apps activities in every situation!

1. Android activity launch modes and tasks Gonçalo Silva / Novoda

4. Activity launch modes and tasks..

5. What is an Activity?

6. Main building block of Android applications

7. HelloWorldActivity.java public class HelloWorldActivity extends Activity { .... }

8. AndroidManifest.xml <? xml version = &quot;1.0&quot; encoding = &quot;utf-8&quot; ?> < manifest xmlns:android = &quot;http://schemas.android.com/apk/res/android&quot; package = &quot;com.novoda.jax&quot; android:versionCode = &quot;1&quot; android:versionName = &quot;1.0&quot; > < application > < activity android:name = &quot;.HelloWorldActivity&quot; /> </ application > </ manifest >

9. Activity task Sequence of related activities a user follows

14. Activity stack / back stack

15. How are activites started?

16. Messaging facility for late run-time binding between components Intents!

18. Explicit intent resolution Intent intent = new Intent( this , HelloWorldActivity. class ); startActivity(intent);

19. Implicit intent resolution Uri google = Uri. parse ( &quot;http://www.google.com&quot; ); Intent intent = new Intent( Intent. ACTION_VIEW , google); startActivity(intent);

20. Intent filter < activity android:name = &quot;.SimpleBrowser&quot; > < intent-filter > < action android:name = &quot;android.intent.action.VIEW&quot; /> < category android:name = &quot;android.intent.category.DEFAULT&quot; /> < data android:scheme = &quot;http&quot; /> </ intent-filter > </activity>

21. Intents are great! Loosely coupled activities Specify your behaviour as intentions

22. Activity re-use Starting an activity in a different application

23. Task Twitter

24. Task Twitter

25. Task Twitter Gmail

26. Activity re-use Some activities are started in a different task

27. Task A Gmail

28. Task A Gmail Task B Browser

29. Activity re-use Allows user to resume after leaving original task Why different tasks?

30. How can we resume an activity?

32. Resuming an activity

33. Resuming a “killed” activity

34. How can we choose a specific task behaviour for our activities?

35. Activity launch modes Define how a new instance of an activity is associated with the current task

37. Defined in the manifest < activity android:launchMode = &quot;singleTop&quot; android:name = &quot;.HelloWorldActivity&quot; />

38. Set as a flag in an intent Intent intent = new Intent( this , HelloWorldActivity. class ); intent.addFlags(Intent. FLAG_ACTIVITY_SINGLE_TOP ); startActivity(intent);

39. Demo App!!! Search the market for: launchmode

40. standard – default launch mode

41. singleTop A new activity X will not be started if there is an activity X on top of the stack onNewIntent() will be called instead of the normal activity lifecycle

42. singleTask Created at the root of a new task Only one instance of the activity can exist at a time onNewIntent() is called if an instance of the activity already exists

43. singleInstance Like singleTop but the only member of its task Any activities started will open in a separate task.

45. Intent flags and launchModes

46. FLAG_ACTIVITY_SINGLE_TOP

47. FLAG_ACTIVITY_MULTIPLE_TASK FLAG_ACTIVITY_NEW_TASK Force an activity to a new task Not recommended!

48. FLAG_ACTIVITY_NO_HISTORY

49. FLAG_ACTIVITY_CLEAR_TOP

50. FLAG_ACTIVITY_REORDER_TO_FRONT

51. FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS The new activity is not kept in the list of recently launched activities

52. FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET FLAG_ACTIVITY_RESET_TASK_IF_NEEDED

53. Other manifest attributes to help deal with activities and tasks

59. singleTask and singleInstance change the UI flow Use with caution!

60. singleTask UI flow

64. singleInstance UI flow

70. Two launcher icons

71. Provide a launcher icon for each singleTask / singleInstance activity

72. Another disadvantage: startActivityForResult()

73. Recommended launchModes: standard and singleTop with intent flags combinations will suit most use cases

75. Thank you for listening! Any Questions?