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

Transcript

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   Clean, Easy & New Android Architecture Britt Barak Devoxx Belgium

   2017
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   Britt Barak @brittBarak Android Developer & TL Android Academy Women

   Techmakers
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   And you...?

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   One thing is sure Everything will change. Quick.

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   My First Startup

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   “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:״
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   Players Exits and Entrances Plays a part → Single responsibility

   → Defined interfaces → Separation of concerns
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   Our Goals - Write quicker - Change easily - Rely

   on the code (test) - Easy for others to understand
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   App Architecture with the new components

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    Who loves Jelly Beans?

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    None
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    None
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    None
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    None
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    Where to start?

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    Presentation Layer Data Layer Domain Layer

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    None
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    Is about: UI Is not about: logic. Presentation Layer

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

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

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

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    UI represents the ViewModel state

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    Presentation Layer Domain Layer View ViewModel User Input

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    1. Update the viewModel

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

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

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    - Callbacks - Data binding - RxJava - LiveData How

    to notify?
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    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
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    public class JellyBeanViewModel extends ViewModel { String flavor; LiveData<Integer> r;

    LiveData<Integer> g; LiveData<Integer> b;
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    public class JellyBeanViewModel extends ViewModel { LiveData<Integer> r; public void

    setR(int r) { r = validate(r); this.r.setValue(r); }
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    3. Create an observer

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

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    4. Observe ViewModel changes

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

    will be removed as the lifecycle ends. LivaData
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    Presentation Layer Domain Layer ViewModel View set() User Input notify

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    Persisting ViewModel

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    None
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    setViewModel() -> { this.viewModel = ViewModelProviders.of(this) .get(JellyBeanViewModel.class); }

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    And for more complex ViewModels?

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

    Suggestions: Peach Dream Peach Pie P
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    Save The Jelly Bean!

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

    consumer Data Layer
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    - Data Model - Repository Data Layer

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

    class JellyBean String flavor; String color;
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    - 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
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    class JellyBeanRepo{ }

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

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

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

    return myFirebaseClient.getJellyBean(id) } }
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    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) }
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    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) }
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    Presentation Layer Data Layer ViewModel DataModel ?

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    Presentation Layer Data Layer Domain Layer DataModel Interactor ViewModel

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

    Layer
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    Save The Jelly Bean!

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    1. Create Use Case

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    class SaveJellyBean extends UseCase { void execute() { }

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    2. Convert Models

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

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

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

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

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

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    Presentation Layer Data Layer Domain Layer DataModel Interactor ViewModel

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

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    Reusing interactors - Edit Jelly Bean screen - Different UI

    - Same SaveJellyBean use case
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    Some more about Repository...

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    Data Layer Network Service Local DB Cache? Domain Layer Some

    Usecase
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    Local database - Persistence between sessions - Single source of

    truth
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    Room - Wraps SQLite database - Generates boilerplate code -

    Verifies queries at compile time - Denies calls on the UI thread
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    1. Create Entity

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

    flavor; String color;
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    2. Create Dao

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

    getAllJellyBeans(); @Query("select * from jellyBean where id = :beanId") LiveData<JellyBean> getJellyBean(String beanId); }
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    @Insert(onConflict = REPLACE) void insertJellyBean(JellyBean jellyBean); @Delete void deleteJellyBean(JellyBean jellyBean);

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    3. Create App Database instance

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

    extends RoomDatabase { private static AppDatabase instance; public abstract JellyBeanDao jellyBeanDao(); //init and destroy code.. }
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    public static AppDatabase getInMemoryDatabase(Context appContext){ if (instance == null) {

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

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

    //... }
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    Presentation Layer Data Layer Domain Layer SaveJellyBean .execute() JellyBeanRepo .save()

    LocalDB JellyBeanDao
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    Presentation Layer • View • ViewModel • Presenter Data Layer

    • Repository • DataModel Domain Layer • Interactor • Use case
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    Players Exits and Entrances Plays a part → Single responsibility

    → Defined interfaces → Separation of concerns
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    Our Goals - Write quicker - Change easily - Rely

    on the code (test) - Easy for others to understand
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    Get my notes on - @britt.barak Keep in touch! Britt

    Barak @brittBarak Thank you!
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    Thank You !