Android architecture components

Android architecture components

• 1.
  Architecture Components + DiegoNascimento Software Engineer at CESAR
• 2.
  What are thegoals of these "architecture components" ?
• 3.
  Architecture Components -API - Room - ViewModel - LiveData - Lifecycle
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  * Taken fromthe book O'Reilly Head First "Design Patterns" The one who is listening is Observer... And the other one, who is emitting events, is subject or observable.
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  LiveData public LiveData<Films> getFilms(){ final MutableLiveData<Films> data = new MutableLiveData<>(); webService.getFilms().enqueue(new Callback<Films>() { @Override public void onResponse(Call<Films> call, Response<Films> response) { data.setValue(response.body()); } }); return data; } // Update the list when the data changes viewModel.getFilms().observe(this, new Observer<Films>() { @Override public void onChanged(@Nullable Films films) { if (films != null) { lstFilms.setAdapter(new FilmsAdapter(getApplicationContext(), films.results); } });
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  Configuration Change onCreate onStart onResume onPause onStop onDestroy onStart onResume onCreate Activity Created ActivityRotated onCleared ViewModel Scope
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  ViewModel The ViewModel classis designed to store and manage UI-related data so that the data survives configuration changes such as screen rotations. public class MyViewModel extends ViewModel { private MutableLiveData<List<User>> users; public LiveData<List<User>> getUsers() { if (users == null) { users = new MutableLiveData<List<Users>>(); loadUsers(); } return users; } private void loadUsers() { // do async operation to fetch users } } public void onCreate(Bundle savedInstanceState) { MyViewModel model = ViewModelProviders.of(this).get(MyViewModel.class); model.getUsers().observe(this, users -> { // update UI }); }
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  Handling Lifecycle The android.arch.lifecyclepackage provides classes and interfaces that let you build lifecycle-aware components — which are components that can automatically adjust their behavior based on the current lifecycle of an activity or fragment
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  LifecycleOwner LifecycleOwner is asingle method interface that denotes that the class has a Lifecycle. It has one method, getLifecycle(), which must be implemented by the class. public class MyFragment extends Fragment implements LifecycleRegistryOwner { LifecycleRegistry lifecycleRegistry = new LifecycleRegistry(this); @Override public LifecycleRegistry getLifecycle() { return lifecycleRegistry; } }
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  LifecycleObserver LifecycleObserver observe LifecycleOwners,and are notified of lifecycle changes. public class MyObserver implements LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) public void onResume() { } @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) public void onPause() { } } aLifecycleOwner.getLifecycle().addObserver(new MyObserver());
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  See more... https://developer.android.com/topic/libraries/architecture/index.htm l https://www.youtube.com/watch?v=FrteWKKVyzI&list=PLOU2XLYxm sIKC8eODk_RNCWv3fBcLvMMy&t=1886s&index=13