Introduction to Dagger 2 - Speaker Deck

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Introduction to Dagger 2 Marcello Galhardo

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@marcellogalhardo @marcellogalhardo @MarcelloGalhard [email protected] /marcellogalhardo Android Dev BR slack.androiddevbr.org

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Do you know... ...inversion of control?

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Do you know... ...inversion of control? ...Dagger?

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Why should I use Dependency Injection?

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Easy reuse of components

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Safer and easier refactoring

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Easier testing

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Activity

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Presenter Activity

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Presenter Repository Activity

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Presenter Repository Activity Api

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Presenter Repository Activity Cache Api

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public class Activity extends AppCompatActivity { private Presenter presenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); presenter = new Presenter(); } } public class Presenter { private Repository repository; public Presenter() { repository = new Repository(); } } Activity.java / Presenter.java

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public class Activity extends AppCompatActivity { private Presenter presenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); presenter = new Presenter(); } } public class Presenter { private Repository repository; public Presenter() { repository = new Repository(); } } Activity.java / Presenter.java

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public class Activity extends AppCompatActivity { private Presenter presenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); Api api = new Api(); Cache cache = new Cache(); Repository repository = new Repository(api, cache); presenter = new Presenter(repository); } } Activity.java

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public class Activity extends AppCompatActivity { private Presenter presenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); Api api = new Api(); Cache cache = new Cache(); Repository repository = new Repository(api, cache); presenter = new Presenter(repository); } } Activity.java

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● Too much boilerplate code; Problems!

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● Too much boilerplate code; ● Hard to maintain the dependency graph. Problems!

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Let's talk about Dagger

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Dagger 2 ● No Reflection;

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Dagger 2 ● No Reflection; ● Code generated at build time;

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Dagger 2 ● No Reflection; ● Code generated at build time; ● Easy to debug;

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Dagger 2 ● No Reflection; ● Code generated at build time; ● Easy to debug; ● Easy to maintain the dependency graph.

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app/build.gradle dependencies { annotationProcessor "com.google.dagger:dagger-compiler:2.8" compile "com.google.dagger:dagger:2.8" provided "org.glassfish:javax.annotation:2.8" }

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@Singleton @Component(modules = { MainModule.class, ...}) public interface MainComponent { void inject(Activity activity); } MainComponent.java

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@Singleton @Component(modules = { MainModule.class, ...}) public interface MainComponent { void inject(Activity activity); } MainComponent.java

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@Singleton @Component(modules = { MainModule.class, ...}) public interface MainComponent { void inject(Activity activity); } MainComponent.java

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@Singleton @Component(modules = { MainModule.class, ...}) public interface MainComponent { void inject(Activity activity); } MainComponent.java

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@Singleton @Component(modules = { MainModule.class, ...}) public interface MainComponent { void inject(Activity activity); } MainComponent.java

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@Singleton @Component(modules = { MainModule.class, ...}) public interface MainComponent { void inject(Activity activity); } MainComponent.java

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MainModule.java @Module public class MainModule { private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024; private static final int TIMEOUT = 20; @Provides public Presenter providesPresenter(Repository repository) { return new Presenter(repository); } @Provides @Reusable public Repository repository(Cache cache, Api api) { return new Repository(cache, api); } @Provides @Singleton public Cache providesCache() { return new Cache(CACHE_SIZE_10_MB); } @Provides @Reusable public Api providesApi() { return new Api(TIMEOUT); } }

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MainModule.java @Module public class MainModule { private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024; private static final int TIMEOUT = 20; @Provides public Presenter providesPresenter(Repository repository) { return new Presenter(repository); } @Provides @Reusable public Repository repository(Cache cache, Api api) { return new Repository(cache, api); } @Provides @Singleton public Cache providesCache() { return new Cache(CACHE_SIZE_10_MB); } @Provides @Reusable public Api providesApi() { return new Api(TIMEOUT); } }

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MainModule.java @Module public class MainModule { private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024; private static final int TIMEOUT = 20; @Provides public Presenter providesPresenter(Repository repository) { return new Presenter(repository); } @Provides @Reusable public Repository repository(Cache cache, Api api) { return new Repository(cache, api); } @Provides @Singleton public Cache providesCache() { return new Cache(CACHE_SIZE_10_MB); } @Provides @Reusable public Api providesApi() { return new Api(TIMEOUT); } }

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MainModule.java @Module public class MainModule { private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024; private static final int TIMEOUT = 20; @Provides public Presenter providesPresenter(Repository repository) { return new Presenter(repository); } @Provides @Reusable public Repository repository(Cache cache, Api api) { return new Repository(cache, api); } @Provides @Singleton public Cache providesCache() { return new Cache(CACHE_SIZE_10_MB); } @Provides @Reusable public Api providesApi() { return new Api(TIMEOUT); } }

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MainModule.java @Module public class MainModule { private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024; private static final int TIMEOUT = 20; @Provides public Presenter providesPresenter(Repository repository) { return new Presenter(repository); } @Provides @Reusable public Repository repository(Cache cache, Api api) { return new Repository(cache, api); } @Provides @Singleton public Cache providesCache() { return new Cache(CACHE_SIZE_10_MB); } @Provides @Reusable public Api providesApi() { return new Api(TIMEOUT); } }

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MainModule.java @Module public class MainModule { private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024; private static final int TIMEOUT = 20; @Provides public Presenter providesPresenter(Repository repository) { return new Presenter(repository); } @Provides @Reusable public Repository repository(Cache cache, Api api) { return new Repository(cache, api); } @Provides @Singleton public Cache providesCache() { return new Cache(CACHE_SIZE_10_MB); } @Provides @Reusable public Api providesApi() { return new Api(TIMEOUT); } }

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MainModule.java @Module public class MainModule { private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024; private static final int TIMEOUT = 20; @Provides public Presenter providesPresenter(Repository repository) { return new Presenter(repository); } @Provides @Reusable public Repository repository(Cache cache, Api api) { return new Repository(cache, api); } @Provides @Singleton public Cache providesCache() { return new Cache(CACHE_SIZE_10_MB); } @Provides @Reusable public Api providesApi() { return new Api(TIMEOUT); } }

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MainModule.java @Module public class MainModule { private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024; private static final int TIMEOUT = 20; @Provides public Presenter providesPresenter(Repository repository) { return new Presenter(repository); } @Provides @Reusable public Repository repository(Cache cache, Api api) { return new Repository(cache, api); } @Provides @Singleton public Cache providesCache() { return new Cache(CACHE_SIZE_10_MB); } @Provides @Reusable public Api providesApi() { return new Api(TIMEOUT); } }

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MainModule.java @Module public class MainModule { private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024; private static final int TIMEOUT = 20; @Provides public Presenter providesPresenter(Repository repository) { return new Presenter(repository); } @Provides @Reusable public Repository repository(Cache cache, Api api) { return new Repository(cache, api); } @Provides @Singleton public Cache providesCache() { return new Cache(CACHE_SIZE_10_MB); } @Provides @Reusable public Api providesApi() { return new Api(TIMEOUT); } }

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MainApplication.java public class MainApplication extends Application { private MainComponent component; @Override public void onCreate() { super.onCreate(); component = DaggerMainComponent.builder().build(); } public MainComponent getComponent() { return component; } }

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MainApplication.java public class MainApplication extends Application { private MainComponent component; @Override public void onCreate() { super.onCreate(); component = DaggerMainComponent.builder().build(); } public MainComponent getComponent() { return component; } }

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MainApplication.java public class MainApplication extends Application { private MainComponent component; @Override public void onCreate() { super.onCreate(); component = DaggerMainComponent.builder().build(); } public MainComponent getComponent() { return component; } }

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MainApplication.java public class MainApplication extends Application { private MainComponent component; @Override public void onCreate() { super.onCreate(); component = DaggerMainComponent.builder().build(); } public MainComponent getComponent() { return component; } }

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Activity

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Application Activity

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Application Component Activity

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Application Component Activity MainModule

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Application Component Activity Modules... MainModule

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Activity.java public class Activity extends AppCompatActivity { @Inject Presenter presenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); MainApplication application = getMainApplication(); MainComponent component = application.getComponent(); component.inject(this); } }

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Activity.java public class Activity extends AppCompatActivity { @Inject Presenter presenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); MainApplication application = getMainApplication(); MainComponent component = application.getComponent(); component.inject(this); } }

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Activity.java public class Activity extends AppCompatActivity { @Inject Presenter presenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); MainApplication application = getMainApplication(); MainComponent component = application.getComponent(); component.inject(this); } }

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Activity.java public class Activity extends AppCompatActivity { @Inject Presenter presenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); MainApplication application = getMainApplication(); MainComponent component = application.getComponent(); component.inject(this); } }

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Repository Cache Api

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Repository MockCache MockApi Api Cache

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Examples

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github.com/marcellogalhardo/events

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github.com/marcellogalhardo/locations

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Questions?

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