1.
Christian Panadero
http://panavtec.me
@PaNaVTEC
Github - PaNaVTEC
My way to clean Android

2.
Fernando Cejas Jorge Barroso
Pedro Gomez Sergio Rodrigo
@fernando_cejas @flipper83
@pedro_g_s @srodrigoDev
Android developer @ Sound Cloud
Android developer @ Tuenti
Cofounder & Android expert @ Karumi
Android developer @ Develapps
Alberto Moraga Carlos Morera
@albertomoraga @CarlosMChica
iOS Developer @ Selltag Android Developer @ Viagogo
Acknowledgements

3.
“My way to clean Android”

4.
Why clean architecture?
• Independent of Frameworks
• Testable
• Independent of UI
• Independent of Database
• Independent of any external agency

5.
Concepts
• Command pattern (Invoker, command, receiver)
• Interactors / Use cases
• Abstractions
• Data Source
• Repository

6.
Abstraction levels
Presenters
Interactors
Entities
Repository
Data sources
UI
Abstractions

7.
The dependency rule
Presenters
Interactors
Entities
Repository
Data sources
UI
Abstractions

8.
Thinking in projects
• App (UI, DI and implementation details)
• Presentation
• Domain y Entities
• Repository
• Data Sources

9.
Project dependencies
App
Presenters Domain Data
Entities
Repository

10.
Flow
View
Presenter
Presenter
Interactor
Interactor
Interactor
Interactor
Repository
Repository
DataSource
DataSource
DataSource

11.
UI: MVP
ViewPresenter(s)
Model
Events
Fill the view
Actions Actions output

12.
UI: MVP - View
public class MainActivity extends BaseActivity implements MainView {
@Inject MainPresenter presenter;
@Override protected void onResume() {
super.onResume();
presenter.onResume();
}
@Override public void onRefresh() {
presenter.onRefresh();
}

13.
UI: MVP - Presenter
public class MainPresenter extends Presenter {
private MainView mainView;
private Bus bus;
public void onResume() {
bus.register(this);
}
public void onPause() {
bus.unregister(this);
}
public void onRefresh() {
mainView.clearData();
…
}

14.
public interface MainView {
void showGetContactsError();
void clearData();
}
UI: MVP - Presenter

15.
Presentation - Domain
Presenter InteractorInvoker
Bus
Bus IMP
Invoker IMP

16.
Presentation - Domain
public class MainPresenter extends Presenter {
public void onCreate() {
interactorInvoker.execute(getContactsInteractor);
}
public void onEvent(GetContactsEvent event) {
if (event.getError() == null) {
List<PresentationContact> contacts = event.getContacts();
mainView.refreshContactsList(contacts);
} else {
mainView.showGetContactsError();
}
}

17.
public class GetContactsInteractor implements Interactor {
private Bus bus;
private ContactsRepository repository;
@Override public void execute() {
GetContactsEvent event = new GetContactsEvent();
try {
List<Contact> contacts = repository.obtainContacts();
event.setContacts(contacts);
} catch (RetrieveContactsException e) {
event.setError(e);
}
bus.post(event);
}
}
Domain - Interactor

18.
Repository
Network
Data Source
BDD
Data Source
Repository
Model
Data

19.
Repository Interface
public interface ContactsRepository {
List<Contact> obtainContacts() throws
CantRetrieveContactsException;
Contact obtain(String md5) throws
CannotObtainContactException;
}

20.
Repository imp
@Override public List<Contact> obtainContacts() throws
RetrieveContactsException {
List<Contact> contacts = null;
try {
contacts = bddDataSource.obtainContacts();
} catch (ObtainContactsBddException | InvalidCacheException e) {
try {
contacts = networkDataSource.obtainContacts();
bddDataSource.persist(contacts);
} catch (UnknownObtainContactsException | ContactsNetworkException) {
throw new RetrieveContactsException();
} catch (PersistContactsBddException) {
e.printStackTrace();
}
}
return contacts;
}

21.
Data source
Model
Data source Imp
Data source
Mapper

22.
Data source Interface
public interface ContactsNetworkDataSource {
public List<Contact> obtainContacts() throws
ContactsNetworkException, UnknownObtainContactsException;
}

23.
private ContactsApiService apiService;
private static final ApiContactMapper mapper = new ApiContactMapper();
@Override public List<Contact> obtainContacts() throws ContactsNetworkException
{
try {
ApiContactsResponse apiContactsResponse = apiService.obtainUsers(100);
List<ApiContactResult> results = apiContactsResponse.getResults();
<MAP APICONTACTS TO CONTACTS>
return contacts;
} catch (Throwable e) {
throw new ContactsNetworkException();
}
}
Data source imp

24.
Caching Strategy
public interface CachingStrategy<T> {
boolean isValid(T data);
}
public TtlCachingStrategy(int ttl, TimeUnit timeUnit) {
ttlMillis = timeUnit.toMillis(ttl);
}
@Override public boolean isValid(T data) {
return (data.getPersistedTime() + ttlMillis) >
System.currentTimeMillis();
}

25.
Caching Strategy
@Override public List<Contact> obtainContacts()
throws ObtainContactsBddException, UnknownObtainContactsException,
InvalidCacheException {
try {
List<BddContact> bddContacts = daoContacts.queryForAll();
if (!cachingStrategy.isValid(bddContacts)) {
deleteBddContacts(cachingStrategy.candidatesToPurgue(bddContacts));
throw new InvalidCacheException();
}
ArrayList<Contact> contacts = new ArrayList<>();
for (BddContact bddContact : bddContacts) {
contacts.add(transformer.transform(bddContact, Contact.class));
}
return contacts;
} catch (java.sql.SQLException e) {
throw new ObtainContactsBddException();
} catch (Throwable e) {
throw new UnknownObtainContactsException();
}
}

26.
Repository adavantages
• Bussines logic doesn’t know where the data came
from
• It’s easy to change data source implementation
• If you change the data sources implementation the
business logic is not altered

27.
– Uncle Bob
“Make implementation details swappable”

28.
Picasso
public interface ImageLoader {
public void load(String url, ImageView imageView);
public void loadCircular(String url, ImageView imageView);
}
public class PicassoImageLoader implements ImageLoader {
private Picasso picasso;
public PicassoImageLoader(Picasso picasso) {
this.picasso = picasso;
}
public void load(String url, ImageView imageView) {
picasso.load(url).into(imageView);
}
@Override public void loadCircular(String url, ImageView imageView) {
picasso.load(url).transform(new CircleTransform()).into(imageView);
}

29.
ErrorManager
public interface ErrorManager {
public void showError(String error);
}
public class SnackbarErrorManagerImp implements ErrorManager {
@Override public void showError(String error) {
SnackbarManager.show(Snackbar.with(activity).text(error));
}
}
public class ToastErrorManagerImp implements ErrorManager {
@Override public void showError(String error) {
Toast.makeText(activity, error,
Toast.LENGTH_LONG).show();
}
}

30.
Tips
• ALWAYS Depend upon abstractions, NEVER
depend upon concretions
• Use a good naming, if there's a class you've
created and the naming does not feel right, most
probably it is wrong modeled.
• Create new shapes using the initial dartboard to
ensure that it's placed on the corresponding layer

31.
– Uncle Bob
“Clean code. The last programming
language”

32.
In Uncle Bob we trust

33.
Show me the code!
https://github.com/PaNaVTEC/Clean-Contacts

34.
References
• Fernando Cejas - Clean way
• Jorge Barroso - Arquitectura Tuenti
• Pedro Gomez - Dependency Injection
• Pedro Gomez - Desing patterns
• Uncle Bob - The clean architecture

35.
¿Questions?
Christian Panadero
http://panavtec.me
@PaNaVTEC
Github - PaNaVTEC