Building maintainable app #droidconzg

Building maintainable
app with MVP and
Dagger2
KRISTĲAN JURKOVIĆ
ANDROID TEAM LEAD @ INFINUM

We're hiring.
HTTPS://INFINUM.CO/CAREERS

We're an independent
design & development
agency.

INFINUM
• 90+ people in 3 oﬃces
• 15 android developers
• hundreds of projects

“Sometimes when you ﬁll a vacuum, it still
sucks.”
― Dennis Ritchie

PROGRAM TO INTERFACES
NOT IMPLEMENTATIONS

LoginActivity LoginPresenterImpl LoginInteractorImpl
LoginView LoginPresenter LoginInteractor
showLoading()
hideLoading()
setUsernameError()
setPasswordError()
showLoading()
hideLoading()
setUsernameError()
setPasswordError()
login(username, pass)
loginPresenter loginView
loginInteractor
login(username, pass) login(username, pass,
listener)
login(username, pass,
listener)
VIEW PRESENTER MODEL

public interface HomeView {
...
}
public interface HomePresenter {
...
}
public interface CurrencyInteractor {
...
}
VIEW
PRESENTER
MODEL

...
}
VIEW

public class HomeActivity
extends BaseActivity
implements HomeView {
// this is an interface
HomePresenter presenter;
...
}

...
}
PRESENTER

public class HomePresenterImpl
implements HomePresenter {
// interface
private HomeView view;
// and another interface
private CurrencyInteractor interactor;
public HomePresenterImpl(
HomeView view, CurrencyInteractor interactor) {
this.view = view;
this.interactor = interactor;
}
...
}

...
}
MODEL

public class CurrencyInteractorImpl
implements CurrencyInteractor {
...
}

void showCurrencies(List<Currency> currencies);
}
void loadCurrencyList();
}
void getCurrencyList(CurrencyListener listener);
}

private void init() {
presenter = new HomePresenterImpl(this,
new CurrencyInteractorImpl());
presenter.getCurrencyList();
}
@Override
public void showCurrencies(List<Currency> currencies) {
// display data  
}
}

...
@Override
public void loadCurrencyList() {
interactor.getCurrencyList(...);
}
}

...
@Override
public void getCurrencyList(
CurrencyListener listener) {
// do API/DB call
// return result with listener
}
}

VIEW SHOULDN’T CREATE ITS
DEPENDENCIES

JSR 330
• 5 annotations - @Named, @Inject, @Qualiﬁer, @Scope,
@Singleton
• 1 interface - Provider<T>

DAGGER 2
• @Module, @Provides, @Component, @Subcomponent,
ScopedProvider
• Injection into Fields, Constructors, Methods
• Each @Inject has to have its @Provides

APP COMPONENT
HOST
MODULE
CONVERTER
MODULE
CLIENT
MODULE
LOGGER
MODULE
API
MODULE
GSON
MODULE

@Module
public class ApiModule {
@Provides
@Singleton
public ApiService provideApiService(
OkHttpClient client, BaseUrl endpoint,
Converter.Factory converter) {
return RestUtils.createApiService(
client, endpoint, converter,
ApiService.class);
}
}

@Module
public class GsonConverterModule {
@Provides
@Singleton
public Converter.Factory
provideConverter(Gson gson) {
return GsonConverterFactory.create(gson);
}
}

APP COMPONENT
HOST
MODULE
CONVERTER
MODULE
CLIENT
MODULE
LOGGER
MODULE
API
MODULE
GSON
MODULE
EXECUTORS
MODULE

@Component(modules = {
HostModule.class,
GsonConverterModule.class,
ClientModule.class,
LoggerModule.class,
ExecutorsModule.class,
ApiModule.class,
GsonModule.class
})
@Singleton
public interface AppComponent {
}

public class MyApplication extends Application {
protected AppComponent appComponent;
protected void init() {
appComponent = DaggerAppComponent.create();
}
}

HOW CAN WE REUSE THAT
IN OUR ACTIVITIES?

• Inject presenter into view
• Inject view and interactor into presenter

@Module
public class HomeModule {
private HomeView view;
public HomeModule(HomeView view) {
this.view = view;
}
@Provides
public HomeView provideView() {
return view;
}
@Provides
public HomePresenter providePresenter(HomePresenterImpl presenter) {
return presenter;
}
@Provides
public CurrencyInteractor provideInteractor(
CurrencyInteractorImpl interactor) {
return interactor;
}
}

@Inject
public CurrencyInteractorImpl(ApiService service) {
}
}

@Inject
public HomePresenterImpl(HomeView view,
CurrencyInteractor interactor) {
this.view = view;
this.interactor = interactor;
}
}

@Inject
HomePresenter presenter;
}

@Subcomponent(modules = HomeModule.class)
public interface HomeComponent {
void inject(HomeActivity activity);
}

WHAT’S THAT
“SUBCOMPONENT” THING
YOU MENTIONED?

APP COMPONENT
HOST
MODULE
CONVERTER
MODULE
CLIENT
MODULE
LOGGER
MODULE
API
MODULE
GSON
MODULE
HOME
MODULE
HOMECOMPONENT
EXECUTORS
MODULE

...
})
@Singleton
public interface AppComponent {
HomeComponent plus(HomeModule module);
}

public abstract class BaseActivity
extends AppCompatActivity {
Override
protected void onCreate(Bundle savedInstanceState) {
...
injectDependencies(MyApplication.getAppComponent());
}
protected abstract
void injectDependencies(AppComponent appComponent);
}

protected void
injectDependencies(AppComponent appComponent) {
appComponent
.plus(new HomeModule(this))
.inject(this);
}
}

APP COMPONENT
HOST
MODULE
CONVERTER
MODULE
CLIENT
MODULE
LOGGER
MODULE
API
MODULE
GSON
MODULE
HOME
MODULE
HOMECOMPONENT
SESSIONCOMPONENT
SESSION
MODULE
EXECUTORS
MODULE

“If you don’t like testing your product, most
likely your customers won’t like to test it
either.”

APPTESTCOMPONENT
MOCKHOST
MODULE
CONVERTER
MODULE
CLIENT
MODULE
LOGGER
MODULE
API
MODULE
GSON
MODULE
SYNC
EXECUTORS
MODULE

...
MockHostModule.class,
SynchronousExecutorsModule.class,
...
})
@Singleton
public interface AppTestComponent extends AppComponent {
void inject(MyTestApplication app);
}

public class MyTestApplication
extends MyApplication
implements TestLifecycleApplication {
@Override
protected void init() {
appComponent = DaggerAppTestComponent.create();
}
}

protected void enqueueResponse(String filename) {
String body = ResourceUtils.readFromFile(filename);
MockResponse mockResponse =
new MockResponse()
.setBody(body)
.setResponseCode(HttpURLConnection.HTTP_OK);
mockWebServer.enqueue(mockResponse);
}

@Override
public void setup() throws Exception {
super.setup();
controller = Robolectric
.buildActivity(MockActivity.class)
.create()
.start()
.resume()
.visible();
fragment = DashboardDrivingModeFragment.newInstance();
controller.get().getSupportFragmentManager()
.beginTransaction()
.replace(R.id.container, fragment, null)
.commit();
ButterKnife.bind(this, fragment.getView());
}

@Test
public void testEmptyStateNotVisible() {
enqueueResponse(“rest-currency-response.json”);
btnCurrencyList.performClick();
assertThat(emptyView).isNotVisible();
}

THINGS TO REMEMBER
• Orientation change

THINGS TO REMEMBER
• Dagger2 is a powerful tool - make good use of it
• Save yourselves from regression bugs

REFERENCES
• http://antonioleiva.com/mvp-android/
• https://medium.com/@czyrux/presenter-surviving-
orientation-changes-with-
loaders-6da6d86ﬀbbf#.xou7c71uz
• http://frogermcs.github.io/dependency-injection-with-
dagger-2-custom-scopes/
• https://www.youtube.com/watch?v=oK_XtfXPkqw

Any questions?
KRISTĲAN.JURKOVIC@INFINUM.CO
@KJURKOVIC
Visit infinum.co or find us on social networks:
infinum.co infinumco infinumco infinum

Building maintainable app #droidconzg

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