Dagger 2

Learning Dagger 2 from a historical context and examining why things are the way they are.

Transcript

1. The most loved/hated dependency injection framework ever The most loved/hated dependency injection framework ever Dagger 2 Dagger 2
2. Hello! I am Michael Yotive You can find me at @myotive
3. Agenda • Dependency Injection (DI) Review • History of DI on Android • Dagger 2 in a nutshell ◦ How to inject a coffee maker ◦ A more realistic Dagger 2 example • Scopes • Other Random Thoughts
4. Dependency Injection Suuuuper quick review
6. Why? • Reduce, or possibly eliminate, unnecessary dependencies. • Reduce dependency carrying. • Keeps code modular.
7. class StarWarsService(){ public List<Film> getFilms(){ RestAdapter restAdapter = { ... }; StarWarsAPI starWarsAPI = restAdapter.create(StarWarsAPI.class); return starWarsAPI.getFilms(); } } Dependency Injection
8. class StarWarsService(){ private StarWarsAPI starWarsAPI; public StarWarsService(StarWarsAPI starWarsAPI){ this.starWarsAPI = starWarsAPI; } public List<Film> getFilms(){ return starWarsAPI.getFilms(); } } Dependency Injection
9. Android Dependency Injection Hmmmm...
10. Dependency Injection • Not best practice to pass StarWarsAPI to an activity/fragment via a constructor. • If fragment, it’s not really best to pass via newInstance() fragment pattern, either. • A custom setter method is an option, but the “two-step” construction is an anti-pattern.
11. public class StarWarsFragment extends Fragment { // Dependency StarWarsAPI starWarsAPI; @Override public void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); starWarsAPI = StarWarsAPIFactory.createAPI(); } ... } Dependency Injection
12. public class StarWarsAPIFactory{ public static StarWarsAPI create(){ OkClient client = OkClientFactory.create(); RequestInterceptor requestInterceptor = RequestInterceptorFactory.create(); GsonConverter gsonConverter = GsonConverterFactory.create(); RestAdapter.LogLevel logLevel = BuildConfig.LOG_NETWORK ? RestAdapter.LogLevel.FULL : RestAdapter.LogLevel.NONE; RestAdapter adapter = new RestAdapter.Builder() .setClient(client) .setLogLevel(logLevel) .setEndpoint(BuildConfig.API_URL) .setRequestInterceptor(requestInterceptor) .setConverter(gsonConverter) .build(); return adapter.create(StarWarsAPI.class); } } Dependency Injection
13. @Inject StarWarsAPI starWarsAPI; or @Inject public MyClass(StarWarsAPI starWarsAPI){ } Dependency Injection
14. A short, non-comprehensive, skewed history of Dependency Injection Frameworks on Android
15. RoboGuice
16. Roboguice • Android optimized version of Guice, Google’s dependency injection framework. ◦ Guice was created at Google by Bob Lee (and Jessie Wilson) • Features include both View and Class injection.
17. Roboguice @ContentView(R.layout.activity_main) public class MainActivity extends RoboActivity { @InjectView(R.id.btn_getFilms) Button getFilms; @Inject Logger logger; @Inject SWAPI swapi; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setupClickListener(); } private void setupClickListener() { getFilms.setOnClickListener(new View.OnClickListener() { ... }); } }
18. Roboguice @ContentView(R.layout.activity_main) public class MainActivity extends RoboActivity { @InjectView(R.id.btn_getFilms) Button getFilms; @Inject Logger logger; @Inject SWAPI swapi; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setupClickListener(); } private void setupClickListener() { getFilms.setOnClickListener(new View.OnClickListener() { ... }); } }
19. Roboguice @ContentView(R.layout.activity_main) public class MainActivity extends RoboActivity { @InjectView(R.id.btn_getFilms) Button getFilms; @Inject Logger logger; @Inject SWAPI swapi; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setupClickListener(); } private void setupClickListener() { getFilms.setOnClickListener(new View.OnClickListener() { ... }); } } public class RoboActivity extends Activity implements RoboContext { protected HashMap<Key<?>,Object> scopedObjects = new HashMap<Key<?>, Object>(); ... @Override public Map<Key<?>, Object> getScopedObjectMap() { return scopedObjects; } @Override public View onCreateView(String name, Context context, AttributeSet attrs) { if (RoboActivity.shouldInjectOnCreateView(name)) return RoboActivity.injectOnCreateView(name, context, attrs); return super.onCreateView(name, context, attrs); } ... }
20. Roboguice @ContentView(R.layout.activity_main) public class MainActivity extends RoboActivity { @InjectView(R.id.btn_getFilms) Button getFilms; @Inject Logger logger; @Inject SWAPI swapi; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setupClickListener(); } private void setupClickListener() { getFilms.setOnClickListener(new View.OnClickListener() { ... }); } }
21. Roboguice @ContentView(R.layout.activity_main) public class MainActivity extends RoboActivity { @InjectView(R.id.btn_getFilms) Button getFilms; @Inject Logger logger; @Inject SWAPI swapi; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setupClickListener(); } private void setupClickListener() { getFilms.setOnClickListener(new View.OnClickListener() { ... }); } }
22. Roboguice @Singleton public class Logger { public void Log(String tag, String message){ Log.d(tag, message); } }
23. Roboguice @ContentView(R.layout.activity_main) public class MainActivity extends RoboActivity { @InjectView(R.id.btn_getFilms) Button getFilms; @Inject Logger logger; @Inject SWAPI swapi; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setupClickListener(); } private void setupClickListener() { getFilms.setOnClickListener(new View.OnClickListener() { ... }); } }
24. Roboguice public interface SWAPI { @GET("films") Call<SWAPIResponse<List<Film>>> getFilms(); }
25. Roboguice public class RetrofitProvider implements Provider<SWAPI> { @Override public SWAPI get() { Retrofit retrofit = GetRetrofit(); return retrofit.create(SWAPI.class); } private Retrofit GetRetrofit() { GsonBuilder builder = new GsonBuilder(); return new Retrofit.Builder() .baseUrl(BuildConfig.SWAPI_URL) .client(getHttpClient()) .addConverterFactory(GsonConverterFactory.create(builder.create())) .build(); } public OkHttpClient getHttpClient(){ ... } HttpLoggingInterceptor getInterceptor(){ … } }
26. Roboguice public class RetrofitProvider implements Provider<SWAPI> { @Override public SWAPI get() { Retrofit retrofit = GetRetrofit(); return retrofit.create(SWAPI.class); } private Retrofit GetRetrofit() { GsonBuilder builder = new GsonBuilder(); return new Retrofit.Builder() .baseUrl(BuildConfig.SWAPI_URL) .client(getHttpClient()) .addConverterFactory(GsonConverterFactory.create(builder.create())) .build(); } public OkHttpClient getHttpClient(){ ... } HttpLoggingInterceptor getInterceptor(){ … } }
27. Roboguice public class RetrofitModule implements Module { @Override public void configure(Binder binder) { binder.bind(SWAPI.class).toProvider(RetrofitProvider.class); } }
28. Roboguice public class RetrofitModule implements Module { @Override public void configure(Binder binder) { binder.bind(SWAPI.class).toProvider(RetrofitProvider.class); } }
29. Roboguice public class RoboGuiceExampleApplication extends Application { @Override public void onCreate() { super.onCreate(); RoboGuice.getOrCreateBaseApplicationInjector(this, RoboGuice.DEFAULT_STAGE, RoboGuice.newDefaultRoboModule(this), new RetrofitModule()); } }
30. Roboguice public class RoboGuiceExampleApplication extends Application { @Override public void onCreate() { super.onCreate(); RoboGuice.getOrCreateBaseApplicationInjector(this, RoboGuice.DEFAULT_STAGE, RoboGuice.newDefaultRoboModule(this), new RetrofitModule()); } }
31. Roboguice Pros • Binding Discovery • Easy Singleton Creation • Android specific Injections Cons • Configuration Errors occur at runtime. • Slow initialization and injections. • Deprecated (As of August 2016)
32. Dagger (v1)
33. Dagger (v1) • Developed at Square by Jessie Wilson (with guidance from Bob Lee) • Initially targeted resource constrained environments, such as Android. • Try to solve the configuration problems of guice (fail at compile time, not runtime).
34. Dagger (v1) @Module( injects = { MainActivity.class } ) public class AppModule { @Provides public Logger providesLogger(){ return new Logger(); } @Provides @Singleton public SWAPI providesSWAPI(Retrofit retrofit){ return retrofit.create(SWAPI.class); } @Provides public Retrofit providesRetrofit(OkHttpClient httpClient) { … } @Provides public OkHttpClient provideHttpClient(HttpLoggingInterceptor loggingInterceptor){ … } @Provides public HttpLoggingInterceptor provideInterceptor(){ … } }
35. Dagger (v1) @Module( injects = { MainActivity.class } ) public class AppModule { @Provides public Logger providesLogger(){ return new Logger(); } @Provides @Singleton public SWAPI providesSWAPI(Retrofit retrofit){ return retrofit.create(SWAPI.class); } @Provides public Retrofit providesRetrofit(OkHttpClient httpClient) { … } @Provides public OkHttpClient provideHttpClient(HttpLoggingInterceptor loggingInterceptor){ … } @Provides public HttpLoggingInterceptor provideInterceptor(){ … } }
36. Dagger (v1) @Module( injects = { MainActivity.class } ) public class AppModule { @Provides public Logger providesLogger(){ return new Logger(); } @Provides @Singleton public SWAPI providesSWAPI(Retrofit retrofit){ return retrofit.create(SWAPI.class); } @Provides public Retrofit providesRetrofit(OkHttpClient httpClient) { … } @Provides public OkHttpClient provideHttpClient(HttpLoggingInterceptor loggingInterceptor){ … } @Provides public HttpLoggingInterceptor provideInterceptor(){ … } }
37. Dagger (v1) @Module( injects = { MainActivity.class } ) public class AppModule { @Provides public Logger providesLogger(){ return new Logger(); } @Provides @Singleton public SWAPI providesSWAPI(Retrofit retrofit){ return retrofit.create(SWAPI.class); } @Provides public Retrofit providesRetrofit(OkHttpClient httpClient) { … } @Provides public OkHttpClient provideHttpClient(HttpLoggingInterceptor loggingInterceptor){ … } @Provides public HttpLoggingInterceptor provideInterceptor(){ … } }
38. Dagger (v1) @Module( injects = { MainActivity.class } ) public class AppModule { @Provides public Logger providesLogger(){ return new Logger(); } @Provides @Singleton public SWAPI providesSWAPI(Retrofit retrofit){ return retrofit.create(SWAPI.class); } @Provides public Retrofit providesRetrofit(OkHttpClient httpClient) { … } @Provides public OkHttpClient provideHttpClient(HttpLoggingInterceptor loggingInterceptor){ … } @Provides public HttpLoggingInterceptor provideInterceptor(){ … } }
39. Dagger (v1) - Object Graph SWAPI RestAdapter OkClient RequestInterceptor Gson
40. Dagger (v1) public class DaggerApplication extends Application { private ObjectGraph objectGraph; @Override public void onCreate() { super.onCreate(); objectGraph = ObjectGraph.create(new AppModule()); } public void inject(Object object) { objectGraph.inject(object); } public static DaggerApplication Instance(Context context){ return (DaggerApplication)context.getApplicationContext(); } }
41. Dagger (v1) public class DaggerApplication extends Application { private ObjectGraph objectGraph; @Override public void onCreate() { super.onCreate(); objectGraph = ObjectGraph.create(new AppModule()); } public void inject(Object object) { objectGraph.inject(object); } public static DaggerApplication Instance(Context context){ return (DaggerApplication)context.getApplicationContext(); } }
42. Dagger (v1) public class DaggerApplication extends Application { private ObjectGraph objectGraph; @Override public void onCreate() { super.onCreate(); objectGraph = ObjectGraph.create(new AppModule()); } public void inject(Object object) { objectGraph.inject(object); } public static DaggerApplication Instance(Context context){ return (DaggerApplication)context.getApplicationContext(); } }
43. Dagger (v1) public class DaggerApplication extends Application { private ObjectGraph objectGraph; @Override public void onCreate() { super.onCreate(); objectGraph = ObjectGraph.create(new AppModule()); } public void inject(Object object) { objectGraph.inject(object); } public static DaggerApplication Instance(Context context){ return (DaggerApplication)context.getApplicationContext(); } }
44. Dagger (v1) public class MainActivity extends AppCompatActivity { @Inject Logger logger; @Inject SWAPI swapi; Button getFilms; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); DaggerApplication.Instance(this).inject(this); setupClickListener(); } private void setupClickListener() { … } }
45. Dagger (v1) public class MainActivity extends AppCompatActivity { @Inject Logger logger; @Inject SWAPI swapi; Button getFilms; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); DaggerApplication.Instance(this).inject(this); setupClickListener(); } private void setupClickListener() { … } }
46. Dagger (v1) public class MainActivity extends AppCompatActivity { @Inject Logger logger; @Inject SWAPI swapi; Button getFilms; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); DaggerApplication.Instance(this).inject(this); setupClickListener(); } private void setupClickListener() { … } } public class DaggerApplication extends Application { private ObjectGraph objectGraph; @Override public void onCreate() { ... } public void inject(Object object) { objectGraph.inject(object); } public static DaggerApplication Instance(Context context){ return (DaggerApplication)context.getApplicationContext(); } }
47. Dagger (v1) public class MainActivity extends AppCompatActivity { @Inject Logger logger; @Inject SWAPI swapi; Button getFilms; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); DaggerApplication.Instance(this).inject(this); setupClickListener(); } private void setupClickListener() { … } } public class DaggerApplication extends Application { private ObjectGraph objectGraph; @Override public void onCreate() { ... } public void inject(Object object) { objectGraph.inject(object); } public static DaggerApplication Instance(Context context){ return (DaggerApplication)context.getApplicationContext(); } }
48. Dagger (v1) public class MainActivity extends AppCompatActivity { @Inject Logger logger; @Inject SWAPI swapi; Button getFilms; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); DaggerApplication.Instance(this).inject(this); setupClickListener(); } private void setupClickListener() { … } }
49. Dagger (v1) Pros • Activities/Fragments don’t need to extend anything special. • Readable Object Graph. Cons • No Android specific helpers like RoboGuice. • Could not fully analyze object graph. • Issues with ProGuard
50. Dagger 2
51. Dagger 2 • Developed by the Java Core Libraries team at Google. • Improve performance through code generation. ◦ This allowed for better ProGuard support. • Strong focus on traceability - knowing exactly why a configuration error has occurred.
52. Upgrading to Dagger 2 from Dagger 1
53. Dagger 2 dependencies { compile 'com.google.dagger:dagger:2.12' annotationProcessor 'com.google.dagger:dagger-compiler:2.12' }
58. How to inject a Coffee Maker
59. The 3 Parts of Dagger • @Inject What object do we want? • @Module / @Provides How do we construct the object? • @Component Where do you want to inject the object?
60. Coffee Maker
61. Coffee Maker Heater Pump
62. Dagger 2 public class CoffeeMaker { private final Heater heater; private final Pump pump; @Inject CoffeeMaker(Heater heater, Pump pump){ this.heater = heater; this.pump = pump; } public void brew(){ heater.on(); pump.pump(); System.out.print("[_]P ~~~ "); System.out.print("Enjoy!"); heater.off(); } }
63. Dagger 2 interface Heater{ void on(); void off(); } interface Pump { void pump(); }
64. Dagger 2 @Module public class CoffeeModule { @Provides Heater providesHeater(){ return new ElectricHeater(); } @Provides Pump providesPump(){ return new Thermosiphon(); } }
65. Dagger 2 @Module public class CoffeeModule { @Provides Heater providesHeater(){ return new ElectricHeater(); } @Provides Pump providesPump(){ return new Thermosiphon(); } }
66. Dagger 2 @Module public class CoffeeModule { @Provides Heater providesHeater(){ return new ElectricHeater(); } @Provides Pump providesPump(){ return new Thermosiphon(); } }
67. Dagger 2 @Component(modules = { CoffeeModule.class }) public interface CoffeeComponent { CoffeeMaker maker(); }
68. Dagger 2 @Component(modules = { CoffeeModule.class }) public interface CoffeeComponent { CoffeeMaker maker(); }
69. Dagger 2 @Component(modules = { CoffeeModule.class }) public interface CoffeeComponent { CoffeeMaker maker(); } Can be any name you want!
70. Dagger 2 @Generated( value = "dagger.internal.codegen.ComponentProcessor", comments = "https://google.github.io/dagger" ) public final class DaggerCoffeeComponent implements CoffeeComponent { private CoffeeModule coffeeModule; ... @Override public CoffeeMaker maker() { return new CoffeeMaker( Preconditions.checkNotNull( coffeeModule.providesHeater(), "Cannot return null from a non-@Nullable @Provides method"), Preconditions.checkNotNull( coffeeModule.providesPump(), "Cannot return null from a non-@Nullable @Provides method")); } public static final class Builder { … } }
71. Dagger 2 @Generated( value = "dagger.internal.codegen.ComponentProcessor", comments = "https://google.github.io/dagger" ) public final class DaggerCoffeeComponent implements CoffeeComponent { private CoffeeModule coffeeModule; ... @Override public CoffeeMaker maker() { return new CoffeeMaker( Preconditions.checkNotNull( coffeeModule.providesHeater(), "Cannot return null from a non-@Nullable @Provides method"), Preconditions.checkNotNull( coffeeModule.providesPump(), "Cannot return null from a non-@Nullable @Provides method")); } public static final class Builder { … } }
72. Dagger 2 @Generated( value = "dagger.internal.codegen.ComponentProcessor", comments = "https://google.github.io/dagger" ) public final class DaggerCoffeeComponent implements CoffeeComponent { private CoffeeModule coffeeModule; ... @Override public CoffeeMaker maker() { return new CoffeeMaker( Preconditions.checkNotNull( coffeeModule.providesHeater(), "Cannot return null from a non-@Nullable @Provides method"), Preconditions.checkNotNull( coffeeModule.providesPump(), "Cannot return null from a non-@Nullable @Provides method")); } public static final class Builder { … } }
73. Dagger 2 @Generated( value = "dagger.internal.codegen.ComponentProcessor", comments = "https://google.github.io/dagger" ) public final class DaggerCoffeeComponent implements CoffeeComponent { private CoffeeModule coffeeModule; ... @Override public CoffeeMaker maker() { return new CoffeeMaker( Preconditions.checkNotNull( coffeeModule.providesHeater(), "Cannot return null from a non-@Nullable @Provides method"), Preconditions.checkNotNull( coffeeModule.providesPump(), "Cannot return null from a non-@Nullable @Provides method")); } public static final class Builder { … } }
74. Dagger 2 public class Program { public static void main(String[] args){ CoffeeComponent component = DaggerCoffeeComponent.builder() .coffeeModule(new CoffeeModule()) .build(); component.maker().brew(); } }
75. Dagger 2 public class Program { public static void main(String[] args){ CoffeeComponent component = DaggerCoffeeComponent.builder() .coffeeModule(new CoffeeModule()) .build(); component.maker().brew(); } }
76. Dagger 2 public class Program { public static void main(String[] args){ CoffeeComponent component = DaggerCoffeeComponent.builder() .coffeeModule(new CoffeeModule()) .build(); component.maker().brew(); } }
77. Dagger 2 public class Program { public static void main(String[] args){ CoffeeComponent component = DaggerCoffeeComponent.builder() .coffeeModule(new CoffeeModule()) .build(); component.maker().brew(); } }
78. Dagger 2 Pros • Static analysis of entire graph at compile time. • No reflection. • Proguard Safe. Cons • Poor Samples (Especially for Android) • Steep learning curve.
79. Android Example
80. Android Example public class MainActivity extends AppCompatActivity { @Inject SWAPI swapi; private Button getFilms; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); getFilms = (Button)findViewById(R.id.btn_getFilms); ... } private void setupClickListener() { … } }
81. Android Example @Module public class ApplicationModule { @Provides public SWAPI provideSWAPI(Retrofit retrofit){ return retrofit.create(SWAPI.class); } @Provides public Retrofit providesRetrofit(OkHttpClient okHttpClient) { … } @Provides public OkHttpClient providesHttpClient(HttpLoggingInterceptor interceptor){ … } @Provides public HttpLoggingInterceptor providesInterceptor(){ … } }
82. Android Example @Component(modules = { ApplicationModule.class }) public interface ApplicationComponent { void inject(MainActivity mainActivity); }
83. Android Example @Component(modules = { ApplicationModule.class }) public interface ApplicationComponent { void inject(MainActivity mainActivity); } @Component(modules = { CoffeeModule.class }) public interface CoffeeComponent { CoffeeMaker maker(); }
84. Android Example @Component(modules = { ApplicationModule.class }) public interface ApplicationComponent { void inject(MainActivity mainActivity); } Allows property level injection for any @Inject annotation
85. Android Example @Component(modules = { ApplicationModule.class }) public interface ApplicationComponent { void inject(MainActivity mainActivity); } This, too, can be any name you want.
86. Android Example public final class DaggerApplicationComponent implements ApplicationComponent { private ApplicationModule applicationModule; private DaggerApplicationComponent(Builder builder) { initialize(builder); } ... @Override public void inject(MainActivity mainActivity) { injectMainActivity(mainActivity); } private MainActivity injectMainActivity(MainActivity instance) { MainActivity_MembersInjector.injectSwapi( instance, Preconditions.checkNotNull( ..., "Cannot return null from a non-@Nullable @Provides method")); return instance; } ... }
87. Android Example public final class DaggerApplicationComponent implements ApplicationComponent { private ApplicationModule applicationModule; private DaggerApplicationComponent(Builder builder) { initialize(builder); } ... @Override public void inject(MainActivity mainActivity) { injectMainActivity(mainActivity); } private MainActivity injectMainActivity(MainActivity instance) { MainActivity_MembersInjector.injectSwapi( instance, Preconditions.checkNotNull( ..., "Cannot return null from a non-@Nullable @Provides method")); return instance; } ... }
88. Android Example public final class DaggerApplicationComponent implements ApplicationComponent { private ApplicationModule applicationModule; private DaggerApplicationComponent(Builder builder) { initialize(builder); } ... @Override public void inject(MainActivity mainActivity) { injectMainActivity(mainActivity); } private MainActivity injectMainActivity(MainActivity instance) { MainActivity_MembersInjector.injectSwapi( instance, Preconditions.checkNotNull( ..., "Cannot return null from a non-@Nullable @Provides method")); return instance; } ... }
89. Android Example public final class MainActivity_MembersInjector implements MembersInjector<MainActivity> { private final Provider<SWAPI> swapiProvider; ... @Override public void injectMembers(MainActivity instance) { injectSwapi(instance, swapiProvider.get()); } public static void injectSwapi(MainActivity instance, SWAPI swapi) { instance.swapi = swapi; } }
90. Android Example public final class MainActivity_MembersInjector implements MembersInjector<MainActivity> { private final Provider<SWAPI> swapiProvider; ... @Override public void injectMembers(MainActivity instance) { injectSwapi(instance, swapiProvider.get()); } public static void injectSwapi(MainActivity instance, SWAPI swapi) { instance.swapi = swapi; } }
91. Android Example public class Dagger2ExampleApplication extends Application { private ApplicationComponent applicationComponent; @Override public void onCreate() { super.onCreate(); applicationComponent = DaggerApplicationComponent.builder() .applicationModule(new ApplicationModule()) .build(); } public static Dagger2ExampleApplication getApplication(Context context){ return (Dagger2ExampleApplication)context.getApplicationContext(); } public ApplicationComponent getApplicationComponent(){ return applicationComponent; } }
92. Android Example public class Dagger2ExampleApplication extends Application { private ApplicationComponent applicationComponent; @Override public void onCreate() { super.onCreate(); applicationComponent = DaggerApplicationComponent.builder() .applicationModule(new ApplicationModule()) .build(); } public static Dagger2ExampleApplication getApplication(Context context){ return (Dagger2ExampleApplication)context.getApplicationContext(); } public ApplicationComponent getApplicationComponent(){ return applicationComponent; } }
93. Android Example public class Dagger2ExampleApplication extends Application { private ApplicationComponent applicationComponent; @Override public void onCreate() { super.onCreate(); applicationComponent = DaggerApplicationComponent.builder() .applicationModule(new ApplicationModule()) .build(); } public static Dagger2ExampleApplication getApplication(Context context){ return (Dagger2ExampleApplication)context.getApplicationContext(); } public ApplicationComponent getApplicationComponent(){ return applicationComponent; } }
94. Android Example public class Dagger2ExampleApplication extends Application { private ApplicationComponent applicationComponent; @Override public void onCreate() { super.onCreate(); applicationComponent = DaggerApplicationComponent.builder() .applicationModule(new ApplicationModule()) .build(); } public static Dagger2ExampleApplication getApplication(Context context){ return (Dagger2ExampleApplication)context.getApplicationContext(); } public ApplicationComponent getApplicationComponent(){ return applicationComponent; } }
95. Android Example public class MainActivity extends AppCompatActivity { @Inject SWAPI swapi; private Button getFilms; @Override protected void onCreate(Bundle savedInstanceState) { … Dagger2ExampleApplication .getApplication(this) .getApplicationComponent() .inject(this); setupClickListener(); } private void setupClickListener() { … } }
96. Android Example public class MainActivity extends AppCompatActivity { @Inject SWAPI swapi; private Button getFilms; @Override protected void onCreate(Bundle savedInstanceState) { … Dagger2ExampleApplication .getApplication(this) .getApplicationComponent() .inject(this); setupClickListener(); } private void setupClickListener() { … } }
97. Scopes
98. Scopes • Mechanism for creating single instances of classes around as long as the component exists. • Think about “scopes” for functions or methods.
99. Scopes • Dagger comes with one built-in scope: @Singleton ◦ I would advise not using this, though. • Custom scopes aren’t hard to make and create clarity for the life of the instance.
100. Scopes @Scope public @interface ApplicationScope { } @Scope public @interface ActivityScope { }
101. Scopes @Module public class ApplicationModule { @Provides @ApplicationScope public SWAPI provideSWAPI(Retrofit retrofit){ return retrofit.create(SWAPI.class); } ... }
102. Scopes
103. Scopes @ApplicationScope @Component(modules = { ApplicationModule.class }) public interface ApplicationComponent { void inject(MainActivity mainActivity); }
104. Scopes • Custom Scopes allow us to have granular control over singleton creation. • You can only have one Custom Scope per component. • We could create application scoped instances, but it would be more performant to only create/keep objects when you need them. (think “local” singletons)
105. Scopes ApplicationComponent (@ApplicationScope) ActivityComponent (@ActivityScope) ActivityComponent (@ActivityScope) ActivityComponent (@ActivityScope) Fragment/ Presenter Fragment/ Presenter Fragment/ Presenter Application Lifecycle
106. Scopes ApplicationComponent (@ApplicationScope) ActivityComponent (@ActivityScope) ActivityComponent (@ActivityScope) ActivityComponent (@ActivityScope) Fragment/ Presenter Fragment/ Presenter Fragment/ Presenter Application Lifecycle How do we share the entire object graph?
107. Component Dependency • Child components have access to parent component’s object graph. • Allows you to keep components independant (separate scopes). • Explicitly show how dependencies are used across components.
108. Component Dependency @ActivityScope @Component( dependencies = { ApplicationComponent.class }, modules = { ActivityModule.class } ) public interface ActivityComponent { void inject(MainActivity mainActivity); }
109. Component Dependency @ActivityScope @Component( dependencies = { ApplicationComponent.class }, modules = { ActivityModule.class } ) public interface ActivityComponent { void inject(MainActivity mainActivity); }
110. Component Dependency public class MainActivity extends AppCompatActivity { ... private ActivityComponent activityComponent; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ... ApplicationComponent applicationComponent = Dagger2ExampleApplication.getApplication(this) .getApplicationComponent(); activityComponent = DaggerActivityComponent.builder() .applicationComponent(applicationComponent) .build(); activityComponent.inject(this); } ... }
111. Component Dependency public class MainActivity extends AppCompatActivity { ... private ActivityComponent activityComponent; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ... ApplicationComponent applicationComponent = Dagger2ExampleApplication.getApplication(this) .getApplicationComponent(); activityComponent = DaggerActivityComponent.builder() .applicationComponent(applicationComponent) .build(); activityComponent.inject(this); } ... }
112. Component Dependency public class MainActivity extends AppCompatActivity { ... private ActivityComponent activityComponent; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ... ApplicationComponent applicationComponent = Dagger2ExampleApplication.getApplication(this) .getApplicationComponent(); activityComponent = DaggerActivityComponent.builder() .applicationComponent(applicationComponent) .build(); activityComponent.inject(this); } ... }
113. Component Dependency public class MainActivity extends AppCompatActivity { ... private ActivityComponent activityComponent; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ... ApplicationComponent applicationComponent = Dagger2ExampleApplication.getApplication(this) .getApplicationComponent(); activityComponent = DaggerActivityComponent.builder() .applicationComponent(applicationComponent) .build(); activityComponent.inject(this); } ... }
114. Component Dependency public class MainActivity extends AppCompatActivity { ... private ActivityComponent activityComponent; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ... ApplicationComponent applicationComponent = Dagger2ExampleApplication.getApplication(this) .getApplicationComponent(); activityComponent = DaggerActivityComponent.builder() .applicationComponent(applicationComponent) .build(); activityComponent.inject(this); } ... }
115. Subcomponents • Another way to have a relationship between components and keep scopes separate. • Child component is added to parent component. • Because you are adding the child component to the parent, you must manage the life of the child component.
116. Subcomponent @ActivityScope @Subcomponent(modules = { ActivityModule.class }) public interface ActivityComponent { void inject(MainActivity mainActivity); }
117. Subcomponent @ApplicationScope @Component(modules = { ApplicationModule.class }) public interface ApplicationComponent { void inject(MainActivity mainActivity); ActivityComponent plus(ActivityModule activityModule); }
118. Subcomponent public class Dagger2ExampleApplication extends Application { private ApplicationComponent applicationComponent; private ActivityComponent activityComponent; @Override public void onCreate() { super.onCreate(); applicationComponent = DaggerApplicationComponent.builder() .applicationModule(new ApplicationModule()) .build(); } … public ActivityComponent createActivityComponent() { activityComponent = applicationComponent.plus(new ActivityModule()); return activityComponent; } public void releaseActivityComponent() { activityComponent = null; } }
119. Subcomponent public class Dagger2ExampleApplication extends Application { private ApplicationComponent applicationComponent; private ActivityComponent activityComponent; @Override public void onCreate() { super.onCreate(); applicationComponent = DaggerApplicationComponent.builder() .applicationModule(new ApplicationModule()) .build(); } … public ActivityComponent createActivityComponent() { activityComponent = applicationComponent.plus(new ActivityModule()); return activityComponent; } public void releaseActivityComponent() { activityComponent = null; } }
120. Subcomponent public class Dagger2ExampleApplication extends Application { private ApplicationComponent applicationComponent; private ActivityComponent activityComponent; @Override public void onCreate() { super.onCreate(); applicationComponent = DaggerApplicationComponent.builder() .applicationModule(new ApplicationModule()) .build(); } … public ActivityComponent createActivityComponent() { activityComponent = applicationComponent.plus(new ActivityModule()); return activityComponent; } public void releaseActivityComponent() { activityComponent = null; } }
121. Subcomponent public class Dagger2ExampleApplication extends Application { private ApplicationComponent applicationComponent; private ActivityComponent activityComponent; @Override public void onCreate() { super.onCreate(); applicationComponent = DaggerApplicationComponent.builder() .applicationModule(new ApplicationModule()) .build(); } … public ActivityComponent createActivityComponent() { activityComponent = applicationComponent.plus(new ActivityModule()); return activityComponent; } public void releaseActivityComponent() { activityComponent = null; } }
122. Miscellaneous
123. Miscellaneous • More Lessons on Dagger 2 on Caster.io https://caster.io/courses/dagger2/ • Specifically, for testing, checkout “Testing with Dagger 2 and Mockito” https://caster.io/episodes/dagger-2-part-5/
124. Miscellaneous • Dependency Injection Performance - Anton Krasov http://blog.nimbledroid.com/2016/03/07/performance-of-dependency- injection-libraries.html
125. Miscellaneous • Dagger 2.10/2.11 - Added the new AndroidInjector helper class for Android member injection.
126. Conclusion • Dependency Injection allows us keep our code clean, modular, and testable. • The hardest part of Dagger 2 is understanding what is happening under the covers. • Dagger 2, for all of it’s quirks, is still one of the most performant DI frameworks.
127. Any Questions?