Dagger 2 is a dependency injection framework that allows for decoupling of classes through injection of dependencies. It uses modules to provide dependencies, with @Inject used to request dependencies and @Component linking modules and injections. Classes request dependencies through constructor injection or field injection with @Inject. Dagger manages the lifecycle and scoping of dependencies through its component and subcomponent functionality.

1. Dagger 2
INJEÇÃO DE DEPENDÊNCIA

2. Injecão de Dependência
 Dependência é qualquer objeto necessário
para o funcionamento de uma classe;
 Desacoplamento entre classes de alto e
baixo nível;
 Inexistente, manual ou automática.

3. public class ClassA {
private ClassB mClassB;
public ClassA() {
mClassB = new ClassB();
}
}

4. public class ClassA {
private ClassB mClassB;
public ClassA() {
mClassB = new ClassB(new ClassC());
}
}

5. public class ClassA {
private ClassB mClassB;
public ClassA(ClassB classB) {
mClassB = classB;
}
}

6. Bibliotecas
 Guice
 Dagger (v1)
 Dagger 2
 ...

7. Funcionamento
@Bind(R.id.home_iv) ImageView mImageView;
ButterKnife.bind(this, view);
view mImageView
findViewbyId
@Bind
mImageView = (ImageView)view.findViewbyId(R.id.home_iv);

8. Funcionamento
Component Object
“findObjectOfTypeX”
@Inject
Module

9. Exemplo
Retrofit
bit.ly/di-android-meetup

10. Retrofit Service
public class GitHubApi {
public static final int CACHE_SIZE = 5 * 1024 * 1024;
public static <S> S createService(Class<S> serviceClass, Context context) {
HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
final Gson gson = gsonBuilder.create();
OkHttpClient client = new OkHttpClient.Builder()
.addInterceptor(interceptor)
.cache(new Cache(context.getCacheDir(), CACHE_SIZE))
.readTimeout(30, TimeUnit.SECONDS)
.connectTimeout(30, TimeUnit.SECONDS)
.build();
Retrofit retrofit = new Retrofit.Builder()
.addConverterFactory(GsonConverterFactory.create(gson))
.baseUrl(BuildConfig.API_URL)
.client(client)
.build();
return retrofit.create(serviceClass);
}
}

11. UserModel
public class GitHubUserModel {
private final GitHubService mService;
public GitHubUserModel(Context context) {
mService = GitHubApi.createService(GitHubService.class, context);
}
public Call<List<GitHubUser>> fetchUsers(int page) {
return mService.getUsers(page);
}
...
}
GitHubUserModel userModel = new GitHubUserModel(getActivity().getApplicationContext());
mActionInteractor = new UsersListPresenter(this, userModel);
mActionInteractor.loadUsersList(false);

12. Introduzindo Dagger

13. Dagger API
 @Module + @Provides
 Mecanismo para prover dependências
 @Inject
 Mecanismo para requisitar dependências
 @Component
 Ligação entre módulos e injeções

14. Dagger
Project/build.gradle
buildscript {
repositories {
jcenter()
}
dependencies {
classpath 'com.android.tools.build:gradle:1.5.0'
classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8’
}
}
App/build.gradle
apply plugin: 'com.neenbedankt.android-apt'
compile 'com.google.dagger:dagger:2.0.2'
apt 'com.google.dagger:dagger-compiler:2.0.2'
provided 'org.glassfish:javax.annotation:10.0-b28'

15. @Module
public class NetworkModule {
public static final int CACHE_SIZE = 5 * 1024 * 1024;
@Provides
public Retrofit provideRetrofit(Gson gson, OkHttpClient client) {
return new Retrofit.Builder()
.addConverterFactory(GsonConverterFactory.create(gson))
.baseUrl(BuildConfig.API_URL)
.client(client)
.build();
}
@Provides
public OkHttpClient provideHttpClient(HttpLoggingInterceptor interceptor, Cache cache) {
return new OkHttpClient.Builder()
.addInterceptor(interceptor)
.cache(cache)
.connectTimeout(60, TimeUnit.SECONDS)
.readTimeout(60, TimeUnit.SECONDS)
.build();
}
@Provides
public Cache provideCache(Application application) {
return new Cache(application.getCacheDir(), CACHE_SIZE);
}
@Provides
public HttpLoggingInterceptor provideHttpInterceptor() {
HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
return interceptor;
}
@Provides
public Gson provideHttpGson() {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
return gsonBuilder.create();
}
}

16. @Module
public class GitHubModule {
public interface GitHubService {
@GET("/users")
@Headers("Authorization: token " + BuildConfig.GITHUB_TOKEN)
Call<List<GitHubUser>> getUsers();
@GET("/users/{login}")
@Headers("Authorization: token " + BuildConfig.GITHUB_TOKEN)
Call<GitHubUser> getUser(@Path("login") String login);
@GET("/users")
@Headers("Authorization: token " + BuildConfig.GITHUB_TOKEN)
Call<List<GitHubUser>> getUsers(@Query("since") int page);
}
@Provides
public GitHubService provideGitHubService(Retrofit retrofit) {
return retrofit.create(GitHubService.class);
}
}

17. @Module
public class AppModule {
private final Context mApplicationContext;
public AppModule(Context applicationContext) {
mApplicationContext = applicationContext;
}
@Provides
@PerApp
public Context provideApplicationContext() {
return mApplicationContext;
}
}

18. @Component(modules = {AppModule.class, GitHubModule.class, NetworkModule.class})
public interface AppComponent {
void inject(UsersListFragment fragment);
}
DepencyInjectionApplication.java
@NonNull
protected DaggerAppComponent.Builder prepareAppComponent() {
return DaggerAppComponent.builder()
.networkModule(new NetworkModule())
.gitHubModule(new GitHubModule())
.appModule(new AppModule(this));
}

19. GitHubUserModel.java
public class GitHubUserModel {
private final GitHubModule.GitHubService mService;
@Inject
public GitHubUserModel(GitHubModule.GitHubService service) {
mService = service;
}
...
}
UsersListFragment.java
@Inject public GitHubUserModel mUserModel;
@Override
protected void onCreate() {
DepencyInjectionApplication.getAppComponent(getActivity()).inject(this);
}
@Override
protected void onResume() {
mActionInteractor = new UsersListPresenter(this, mUserModel);
mActionInteractor.loadUsersList(false);
}

20. GitHubUserModel
Retrofit
OkHttpClient
Gson
NetworkModule#provideRetrofit
NetworkModule#provideHttpClient
NetworkModule#provideGson
GitHubService GitHubModule#provideGitHubService

21. Component Dependency

22. @Component(modules={AppModule.class, NetworkModule.class})
public interface NetComponent {
Retrofit retrofit();
}
@Component(dependencies = NetComponent.class, modules = GitHubModule.class)
public interface AppComponent {
void inject(UsersListFragment fragment);
}
public class DepencyInjectionApplication extends Application {
private AppComponent mAppComponent;
private NetComponent mNetComponent;
private void setupDaggerAppComponent() {
mNetComponent = DaggerNetComponent.builder()
.appModule(new AppModule(this))
// .networkModule(new NetworkModule()) is free
.build();
mAppComponent = DaggerAppComponent.builder()
// .gitHubModule(new GitHubModule()) is free
.netComponent(mNetComponent)
.build();
}
}

23. Subcomponent

24. @Subcomponent(modules = GitHubModule.class)
public interface GitHubComponent {
void inject(UsersListFragment fragment);
}
@Component(modules = {NetworkModule.class, AppModule.class})
public interface AppComponent {
Application getApplication();
GitHubComponent plus(GitHubModule gitHubModule);
}
DepencyInjectionApplication.java
private void setupDaggerAppComponent() {
mAppComponent = DaggerAppComponent.builder()
.appModule(new AppModule(this))
.build();
}
UsersListFragment.java
@Override
protected void onCreate() {
DepencyInjectionApplication.getAppComponent(getActivity())
.plus(new GitHubModule())
.inject(this);
}
@Override
protected void onResume() {
mActionInteractor = new UsersListPresenter(this, mUserModel);
mActionInteractor.loadUsersList(false);
}

25. Scopes
 Determinam a intenção de duração de ciclo de vida de um
component;
 @Singleton é o único suportado out-of-the-box;
 Deve ser usado no nível de aplicação
 Custom scopes permitem maior flexibilidade, mas cabe
ao programador respeitar o ciclo de vida.

26. @Scope
@Retention(RetentionPolicy.RUNTIME)
public @interface PerActivity {}
@Module
public class MyActivityModule {
@PerActivity
@Named("ActivityScope") @Provides
StringBuilder provideStringBuilderActivityScope() {
return new StringBuilder("Activity");
}
@Named("Unscoped") @Provides
StringBuilder provideStringBuilderUnscoped() {
return new StringBuilder("Unscoped");
}
}

27. public class MyActivity {
@Inject @Named("ActivityScope")
StringBuilder activityScope1;
@Inject @Named("ActivityScope")
StringBuilder activityScope2;
@Inject @Named("Unscoped")
StringBuilder unscoped1;
@Inject @Named("Unscoped")
StringBuilder unscoped2;
public void onCreate() {
activityScope1.append("123");
activityScope1.toString(); // output: "Activity123"
activityScope2.append("456");
activityScope2.toString(); // output: "Activity123456"
unscoped1.append("123");
unscoped1.toString(); // output: "Unscoped123"
unscoped2.append("456");
unscoped2.toString(); // output: "Unscoped456"
}
}

28. Bonus
 Lazy;
 Inicialização de Map e Set;
 Producer assíncrono;

29. Conclusão
 Fácil acesso à variáveis compartilhadas;
 Desacoplamento de dependências complexas;
 Controle de ciclo de vida;
 Performance.

30. Dúvidas?
edson-menegatti-87898718
3dm1
edson.menegatti.7

31. Referências
https://www.youtube.com/watch?v=oK_XtfXPkqw
https://github.com/codepath/android_guides/wiki/Dependenc
y-Injection-with-Dagger-2
https://www.parleys.com/tutorial/5471cdd1e4b065ebcfa1d55
7/
https://blog.gouline.net/2015/05/04/dagger-2-even-sharper-
less-square/
https://www.youtube.com/watch?v=SKFB8u0-VA0