Clean, Easy & New Android Arch. : Devoxx-BE 17

Transcript

1. Clean, Easy & New Android Architecture Britt Barak Devoxx Belgium

   2017

2. Britt Barak @brittBarak Android Developer & TL Android Academy Women

   Techmakers

3. And you...?

4. One thing is sure Everything will change. Quick.

5. My First Startup

6. “As You Like It” / W. Shakespeare ״All the world’s

   a stage, And all the men and women merely players; They have their exits and their entrances, And one man in his time plays many parts:״

7. Players Exits and Entrances Plays a part → Single responsibility

   → Defined interfaces → Separation of concerns

8. Our Goals - Write quicker - Change easily - Rely

   on the code (test) - Easy for others to understand

9. App Architecture with the new components

10. Who loves Jelly Beans?

11. None
12. None
13. None
14. None

15. Where to start?

16. Presentation Layer Data Layer Domain Layer

17. None

18. Is about: UI Is not about: logic. Presentation Layer

19. class JellyBeanViewModel extends ViewModel { String flavor; int r; int

    g; int b;

20. @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_add_bean); setViewModel()

    setUi(); }

21. void setViewModel(){ this.viewModel = new JellyBeanViewModel(); }

22. UI represents the ViewModel state

23. Presentation Layer Domain Layer View ViewModel User Input

24. 1. Update the viewModel

25. public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) { switch

    (seekBar.getId()) { case R.id.sb_r: viewModel.setR(progress); break; //...

26. 2. View Model notifies

27. - Callbacks - Data binding - RxJava - LiveData How

    to notify?

28. LiveData - Observable data holder class - Lifecycle-aware - Updates

    only on started / resumed state - Removes itself on destroyed state - No memory leaks https://developer.android.com/topic/libraries/architecture/livedata.html

29. public class JellyBeanViewModel extends ViewModel { String flavor; LiveData<Integer> r;

    LiveData<Integer> g; LiveData<Integer> b;

30. public class JellyBeanViewModel extends ViewModel { LiveData<Integer> r; public void

    setR(int r) { r = validate(r); this.r.setValue(r); }

31. 3. Create an observer

32. Observer<Integer> colorChangedObserver = (Integer integer) -> { beanIv.setColorFilter(viewModel.getColor()); };

33. 4. Observe ViewModel changes

34. viewModel.getR() .observe(this, colorChangedObserver); Observer is tied to this lifecycle, and

    will be removed as the lifecycle ends. LivaData

35. Presentation Layer Domain Layer ViewModel View set() User Input notify

36. Persisting ViewModel

37. None

38. setViewModel() -> { this.viewModel = ViewModelProviders.of(this) .get(JellyBeanViewModel.class); }

39. And for more complex ViewModels?

40. 1. Multiple LiveData Objects 2. Separate class → Lifecycle Aware

    Suggestions: Peach Dream Peach Pie P

41. Save The Jelly Bean!

42. Is about: “objective” data Is not about: caring about the

    consumer Data Layer

43. - Data Model - Repository Data Layer

44. class JellyBeanViewModel String flavor; int r; int g; int b;

    class JellyBean String flavor; String color;

45. - One per data type (e.g jelly bean, recipe, user….).

    - Encapsulates the logic of getting/setting the data. - CRUD operations (Create, Read, Update, Delete) Repository

46. class JellyBeanRepo{ }

47. class JellyBeanRepo{ LiveData<JellyBean> getJellyBean(String id){ }

48. LiveData<JellyBean> getJellyBean(String id) { return myFirebaseClient.getJellyBean(id) }

49. LiveData<JellyBean> getJellyBean(String id) { if (cache.hasJellyBean(id)){ return cache.getJellyBean(id); } else{

    return myFirebaseClient.getJellyBean(id) } }

50. LiveData<JellyBean> getJellyBean(String id) { if (cache.hasJellyBean(id)){ return cache.getJellyBean(id); } else

    if (appDatabase.hasJellyBean(id)) { return appDatabase.jellyBeanDao().getJellyBean(id); } else{ return myFirebaseClient.getJellyBean(id) }

51. LiveData<JellyBean> getJellyBean(String id) { if (cache.hasJellyBean(id)){ return cache.getJellyBean(id); } else

    if (appDatabase.hasJellyBean(id)) { return appDatabase.jellyBeanDao().getJellyBean(id); } else{ return myApiClient.getJellyBean(id) }

52. Presentation Layer Data Layer ViewModel DataModel ?

53. Presentation Layer Data Layer Domain Layer DataModel Interactor ViewModel

54. Is about: converting models Is not about: UI, Data Domain

    Layer

55. Save The Jelly Bean!

56. 1. Create Use Case

57. class SaveJellyBean extends UseCase { void execute() { }

58. 2. Convert Models

59. public class SaveJellyBean extends UseCase { public void execute(JellyBeanViewModel viewModel)

    { JellyBean data = prepareDataModel(viewModel); }

60. JellyBean prepareDataModel(JellyBeanViewModel viewModel){ String beanColorString = String.format("#%06X", (0xFFFFFF & viewModel.getColor()));

    JellyBean data = new JellyBean(viewModel.getFlavor(), beanColorString); return data; }

61. 3. Call Repository

62. public class SaveJellyBean extends UseCase { public void execute(JellyBeanViewModel viewModel)

    { JellyBean data = prepareDataModel(viewModel); repo.saveBean(data); }

63. 4. Execute

64. Presentation Layer Data Layer Domain Layer DataModel Interactor ViewModel

65. Presentation Layer Data Layer Domain Layer SaveJellyBean .execute() JellyBeanRepo .save()

66. Reusing interactors - Edit Jelly Bean screen - Different UI

    - Same SaveJellyBean use case

67. Some more about Repository...

68. Data Layer Network Service Local DB Cache? Domain Layer Some

    Usecase

69. Local database - Persistence between sessions - Single source of

    truth

70. Room - Wraps SQLite database - Generates boilerplate code -

    Verifies queries at compile time - Denies calls on the UI thread

71. 1. Create Entity

72. @Entity public class JellyBean { @PrimaryKey @NonNull String id; String

    flavor; String color;

73. 2. Create Dao

74. @Dao public interface JellyBeanDao { @Query("select * from jellyBean") LiveData<List<JellyBean>>

    getAllJellyBeans(); @Query("select * from jellyBean where id = :beanId") LiveData<JellyBean> getJellyBean(String beanId); }

75. @Insert(onConflict = REPLACE) void insertJellyBean(JellyBean jellyBean); @Delete void deleteJellyBean(JellyBean jellyBean);

76. 3. Create App Database instance

77. @Database(version = 1, entities = {JellyBean.class}) public abstract class AppDatabase

    extends RoomDatabase { private static AppDatabase instance; public abstract JellyBeanDao jellyBeanDao(); //init and destroy code.. }

78. public static AppDatabase getInMemoryDatabase(Context appContext){ if (instance == null) {

    instance = Room.inMemoryDatabaseBuilder( appContext, AppDatabase.class).build(); } return instance; } public static void destroyInstance() { instance = null; }

79. 4. Use from Repository

80. public LiveData<JellyBean> getJellyBean(String id) { if (cache.hasJellyBean(id)){ //… return appDatabase.jellyBeanDao().getJellyBean(id);

    //... }

81. Presentation Layer Data Layer Domain Layer SaveJellyBean .execute() JellyBeanRepo .save()

    LocalDB JellyBeanDao

82. Presentation Layer • View • ViewModel • Presenter Data Layer

    • Repository • DataModel Domain Layer • Interactor • Use case

83. Players Exits and Entrances Plays a part → Single responsibility

    → Defined interfaces → Separation of concerns

84. Our Goals - Write quicker - Change easily - Rely

    on the code (test) - Easy for others to understand

85. Get my notes on - @britt.barak Keep in touch! Britt

    Barak @brittBarak Thank you!

86. Thank You !