This document summarizes Christian Panadero's presentation on "My way to clean Android". It discusses clean architecture principles for Android applications, including separating components by abstraction level and dependency rules. It outlines the project structure with separate modules for presentation, domain, and data layers. It also provides examples of interactions between these layers using common design patterns like MVP, repositories, and dependency injection. The goal is to make implementations swappable and the codebase independent of frameworks and external factors for maximum testability and flexibility.

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