Architecture Components - IT Step

Talk about recommended Architecture by Google, some architecture patterns and about principle “be together, not the same” - and advices on how to apply Architecture Components to existing projects and with lovely tools

Transcript

1. Architecture Components Constantine Mars Team Lead, Senior Developer @ DataArt Построение современной архитектуры мобильных приложений
2. Background Software Architecture Basics
3. Components: -Activities -Fragments -Services -Content Providers -Broadcast Receivers Android Has “Good Bones”
4. App-hopping OS may kill app at random time App components lifecycle is not under control Components should not depend on each other Can’t rely on data, stored in components There are Everyday Problems to Solve
5. Simply related to Activity Lifecycle
6. -Separation of concerns -Provide solid user experience -Keep UI lean and simple -Keep UI free of app logic -Drive UI from model -Use persistent model -Assign clear responsibilities for each model class Common Principles for staying in mind :)
7. Image from fernandocejas.com Separation of Concerns...
8. Image from fernandocejas.com Clean Architecture
9. -Modular app -Each class responsible for one well-defined function -Should be no god objects -The app should be testable Remember Good Architecture Goals...
10. Android Recommended Architecture
11. Android Recommended Architecture. Another View
12. Be together. not the same
13. “It is impossible to have one way of writing apps that will be the best for every scenario. That being said, this recommended architecture should be a good starting point for most use cases. If you already have a good way of writing Android apps, you don't need to change.” Be together. not the same
14. Building blocks Architecture Components
15. Purpose: Display data and pass on UI events Neither contain the UI data, nor directly manipulate data Examples: Activity, Fragment Views = UI Controllers = LifecycleOwners
16. After the lifecycles API in the Architecture Components becomes stable, the Fragment class in the Android Support Library will implement LifecycleOwner LifecycleActivity, LifecycleFragment
17. ViewModel Data holder for Activity/Fragment Survives configuration changes NEVER references View / Activity / Fragment
18. ViewModel public class DetailActivityViewModel extends ViewModel { private WeatherEntry mWeather; public DetailActivityViewModel() {} public WeatherEntry getWeather() { return mWeather; } public void setWeather(WeatherEntry weatherEntry) { mWeather = weatherEntry; } }
19. ViewModel and Lifecycle
20. ViewModel and LifecycleOwner public class DetailActivity extends LifecycleActivity { DetailActivityViewModel viewModel; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ... viewModel = ViewModelProviders.of(this).get(DetailActivityViewModel.class); } ...
21. Represent data needed for the UI to display An observable data holder Lifecycle aware Automatic subscription management LiveData
22. Observer pattern. Subscription = Observation
23. LiveData sample implementation
24. Live Data public class DetailActivityViewModel extends ViewModel { private MutableLiveData<WeatherEntry> mWeather; public DetailActivityViewModel() {} public MutableLiveData<WeatherEntry> getWeather() { return mWeather; } public void setWeather(WeatherEntry weatherEntry) { mWeather.postValue(weatherEntry); } }
25. Live Data observing public class DetailActivity extends LifecycleActivity { DetailActivityViewModel viewModel; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ... viewModel = ViewModelProviders.of(this).get(DetailActivityViewModel.class); viewModel.getWeather().observe(this, weatherEntry -> { if(weatherEntry!=null) { bindWeatherToUI(weatherEntry); } }); }
26. -Single source of truth -ViewModels simply request data from the repository -Is a mediator between the different data sources Repository pattern Image from fernandocejas.com
27. Manages data from a remote data source, such as the internet May use REST, Cloud Remote Network Data Source
28. Manages local data stored in the database Model
29. Each class in the diagram only stores a reference to the class or classes directly "below it" and not any classes above it Layered architecture pattern
30. ORM from Google Room
31. -Less boilerplate compared to the built-in APIs -Compile-time validation of SQL queries -Data observation via LiveData, RxJava Room ORM purposes
32. -@Entity -@Dao -@Database Room annotations
33. Entity
34. @Entity declaration @Entity(tableName = "weather", indices = {@Index(value = {"date"}, unique = true)}) public class WeatherEntry { @PrimaryKey(autoGenerate = true) private int id; … }
35. @Entity constructors //Room constructor public WeatherEntry(int id, int weatherIconId, Date date, ...) { //Json constructor - ignored by Room @Ignore public WeatherEntry(int weatherIconId, Date date, // (!) Only one constructor should be exposed to Room ...
36. Dao
37. @Dao declaration @Dao public interface WeatherDao { @Query("SELECT * FROM weather") List<WeatherEntry> getAll(); @Insert(onConflict = OnConflictStrategy.REPLACE) void insertAll(WeatherEntry... weatherEntries); @Delete void delete(WeatherEntry weatherEntry); }
38. Database
39. @Database declaration @Database(entities = {WeatherEntry.class}, version = 1) @TypeConverters(DateConverter.class) public abstract class AppDatabase extends RoomDatabase { public abstract WeatherDao weatherDao(); }
40. @Database - a singleton private static final String DATABASE_NAME = "weather"; private static final Object LOCK = new Object(); private static volatile AppDatabase sInstance; public static AppDatabase getInstance(Context context) { if (sInstance == null) { synchronized (LOCK) { if (sInstance == null) { sInstance = Room.databaseBuilder(context.getApplicationContext(), AppDatabase.class, AppDatabase.DATABASE_NAME).build(); } }} return sInstance; }
41. Type converters class DateConverter { @TypeConverter public static Date toDate(Long timestamp) { return timestamp == null ? null : new Date(timestamp); } @TypeConverter public static Long toTimestamp(Date date) { return date == null ? null : date.getTime(); } }
42. Alternatives
43. Repository
44. Repository pattern public class WeatherRepository { public synchronized static WeatherRepository getInstance(); public synchronized void initializeData(); private void deleteOldData(); private boolean isFetchNeeded(); private void startFetchWeatherService(); }
45. Repository - fetch data from network mWeatherNetworkDataSource = weatherNetworkDataSource; LiveData<WeatherEntry[]> networkData = mWeatherNetworkDataSource.getCurrentWeatherForecasts(); networkData.observeForever(newForecastsFromNetwork -> { mExecutors.diskIO().execute(() -> { mWeatherDao.bulkInsert(newForecastsFromNetwork); Log.d(LOG_TAG, "New values inserted"); }); });
46. Repository - use LiveData private WeatherNetworkDataSource(Context context, AppExecutors executors) { mContext = context; mExecutors = executors; mDownloadedWeatherForecasts = new MutableLiveData<WeatherEntry[]>(); }
47. Check when to fetch private boolean isFetchNeeded() { Date today = CustomDateUtils.getNormalizedUtcDateForToday(); int count = mWeatherDao.countAllFutureWeather(today); return (count < WeatherNetworkDataSource.NUM_DAYS); }
48. Check when to fetch public synchronized void initializeData() { if (mInitialized) return; mInitialized = true; mExecutors.diskIO().execute(() -> { if (isFetchNeeded()) { startFetchWeatherService(); } }); }
49. Display the data
50. And again - observe LiveData public class DetailActivity extends LifecycleActivity { DetailActivityViewModel viewModel; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ... viewModel = ViewModelProviders.of(this).get(DetailActivityViewModel.class); viewModel.getWeather().observe(this, weatherEntry -> { if(weatherEntry!=null) { bindWeatherToUI(weatherEntry); } }); }
51. Testing Sneak peek :)
52. UI Controller - Instrumentation
53. ViewModel - JUnit
54. Repository - JUnit, MockWebServer
55. Scalability and advices Almost there...
56. What if... I use RxJava? I already have MVP? I love Kotlin? I’m working on legacy project? Typical questions
57. The Answer is...
58. Read, watch and visit... Links
59. Guide to App Architecture https://developer.android.com/topic/libraries/architecture/guide.html Architecture Components https://developer.android.com/topic/libraries/architecture/index.html I/O ‘17 Architecture Components Introduction - https://youtu.be/FrteWKKVyzI Solving the Lifecycle Problem - https://youtu.be/bEKNi1JOrNs Persistence and Offline - https://youtu.be/MfHsPGQ6bgE Architecture Components on GDD Europe - https://youtu.be/Ts-uxYiBEQ8 GDD Europe CodeLabs g.co/codelabs/gdd17 Google Github samples https://github.com/googlesamples/android-architecture-components What to read and watch :)
60. Moxy https://github.com/Arello-Mobile/Moxy Mosby https://github.com/sockeqwe/mosby Android MVP Helper https://github.com/Ufkoku/AndroidMVPHelper Clean Architecture https://github.com/android10/Android-CleanArchitecture Reark https://github.com/reark/reark MVP + Dagger2 + Rx https://android.jlelse.eu/mvp-dagger-2-rx-clean-modern-android-app-code-74f63c9a6f2f Architecture the Lost Years by Uncle Bob https://youtu.be/WpkDN78P884 Alternatives to consider
61. Where to go :)
62. Where to go :)
63. Where to go :)
64. Thank you! :) Constantine Mars @ConstantineMars +ConstantineMars Mobile Architecture Club