Optimizing Dagger on Android

We'll discuss recent developments in Dagger for Android, both in terms of new APIs in dagger.android and optimizations in generated code. We'll then discuss how to not encounter common pitfalls that decrease runtime performance.

1. Optimizing Dagger on Android Ron Shapiro ronsh@google @rdshapiro
2. Prereqs
3. Prereqs • You've used Dagger before
4. Prereqs • You've used Dagger before • Optional: Understanding Dagger 2's Generated Code ◦ https://goo.gl/toV6Nq
5. Prereqs • You've used Dagger before • Optional: Understanding Dagger 2's Generated Code ◦ https://goo.gl/toV6Nq • You’re not scared to look at generated code
6. Glossary
7. Glossary • Key ! Type + Optional<Qualifier>
8. Glossary • Key ! Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest>
9. Glossary • Key ! Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest> @Provides
 Airplane airplane(
10. Glossary • Key ! Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest> @Provides
 Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }
11. Glossary • Key ! Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest> @Provides
 Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … } • DependencyRequest ! Key + Kind
12. Glossary • Key ! Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest> @Provides
 Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … } • DependencyRequest ! Key + Kind ◦ enum Kind { INSTANCE, PROVIDER, LAZY, … }
13. Glossary • Key ! (normalized) Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest> @Provides
 Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1 • DependencyRequest ! Key + Kind ◦ enum Kind { INSTANCE, PROVIDER, LAZY, … }
14. Glossary • Key ! (normalized) Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest> @Provides
 Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1 
 @Provides
 XWing xWing( Body body, @Left Wing left, @Right Wing right) { … } • DependencyRequest ! Key + Kind ◦ enum Kind { INSTANCE, PROVIDER, LAZY, … }
15. Glossary • Key ! (normalized) Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest> @Provides
 Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1 
 @Provides
 XWing xWing( Body body, @Left Provider<Wing> left, @Right Provider<Wing> right) { … } • DependencyRequest ! Key + Kind ◦ enum Kind { INSTANCE, PROVIDER, LAZY, … }
16. Glossary • Key ! (normalized) Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest> @Provides
 Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1 
 @Provides
 XWing xWing( Body body, @Left Provider<Wing> left, @Right Provider<Wing> right, Logo logo) { … } • DependencyRequest ! Key + Kind ◦ enum Kind { INSTANCE, PROVIDER, LAZY, … }
17. Glossary • Key ! (normalized) Type + Optional<Qualifier> • Binding ! Key + ImmutableSet<DependencyRequest> @Provides
 Airplane airplane( Body body, @Left Wing left, @Right Wing right) { … }1 
 @Provides
 XWing xWing( Body body, @Left Provider<Wing> left, @Right Provider<Wing> right, Lazy<Logo> logo) { … } • DependencyRequest ! Key + Kind ◦ enum Kind { INSTANCE, PROVIDER, LAZY, … }
18. Life of a DependencyRequest java/dagger/internal/codegen/BindingExpression.java
19. Life of a DependencyRequest • How many bindings have this key? java/dagger/internal/codegen/BindingExpression.java
20. Life of a DependencyRequest • How many bindings have this key? ◦ 0 ! missing binding error java/dagger/internal/codegen/BindingExpression.java
21. Life of a DependencyRequest • How many bindings have this key? ◦ 0 ! missing binding error ◦ 2+ ! duplicate binding error java/dagger/internal/codegen/BindingExpression.java
22. Life of a DependencyRequest • How many bindings have this key? ◦ 0 ! missing binding error ◦ 2+ ! duplicate binding error java/dagger/internal/codegen/BindingExpression.java
23. Life of a DependencyRequest • How many bindings have this key? ◦ 0 ! missing binding error ◦ 2+ ! duplicate binding error • How can Binding X be represented as DependencyRequest.Kind Y using X's own dependencies? java/dagger/internal/codegen/BindingExpression.java
24. @Module class AirplaneModule { @Provides Airplane weldAndCreate() {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java
25. @Module class AirplaneModule { @Provides Airplane weldAndCreate(Body body) {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java
26. @Module class AirplaneModule { @Provides Airplane weldAndCreate( Body body, @Left Wing leftWing, @Right Wing rightWing) {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java
27. @Module class AirplaneModule { @Provides Airplane weldAndCreate( Body body, @Left Wing leftWing, @Right Wing rightWing, Welder welder) {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java
28. @Module class AirplaneModule { @Provides Airplane weldAndCreate( Body body, @Left Wing leftWing, @Right Wing rightWing, Welder welder, Lazy<SafetyFeature> lazySafety) {}1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java
29. @Module class AirplaneModule { @Provides Airplane weldAndCreate( Body body, @Left Wing leftWing, @Right Wing rightWing, Welder welder, Lazy<SafetyFeature> lazySafety) { welder.weld(body, leftWing); welder.weld(body, rightWing); if (LAWYERS_REQUIRE_SAFETY_FEATURE) { lazySafety.get().protect(body); } return new Airplane(body); }1 }2 Life of a DependencyRequest java/dagger/internal/codegen/SimpleMethodBindingExpression.java
30. Life of a DependencyRequest @Component(modules = { AirplaneModule.class, WingModule.class, }) interface AirplaneComponent { Airplane createAirplane(); }
31. Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1/* body */,2 1/* left wing */, 1/* right wing */, 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java
32. Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(),2 1/* left wing */, 1/* right wing */, 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java
33. Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1/* left wing */, 1/* right wing */, 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java
34. Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1/* right wing */, 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java
35. Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1/* welder */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java
36. Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1welderProvider.get(), 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java java/dagger/internal/codegen/FrameworkType.java
37. Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1welderProvider.get() /* */, 1/* safety feature */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java java/dagger/internal/codegen/FrameworkType.java
38. Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1welderProvider.get() /* */, 1DoubleCheck.lazy(safetyProvider); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java java/dagger/internal/codegen/FrameworkType.java
39. Life of a DependencyRequest @Override Airplane createAirplane() { airplaneModule.weldAndCreate( 1new Body(new Steel()),2 1WingModule.createLeftWing(new Steel()), 1WingModule.createRightWing(new Steel(), new Logo()), 1welderProvider.get() /* */, 1DoubleCheck.lazy(safetyProvider /* */); } java/dagger/internal/codegen/SimpleMethodBindingExpression.java java/dagger/internal/codegen/FrameworkType.java
40. Life of a component initialization private void initialize() { this.welderProvider =1 }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java
41. Life of a component initialization private void initialize() { this.welderProvider =1 new Provider<Welder>() { @Override public Welder get()3{}4 }; }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java
42. Life of a component initialization private void initialize() { this.welderProvider =15 6new Provider<Welder>() { @Override public Welder get()3{ return new Welder( new Wire(), new ProtectiveShield(), flamethrowerProvider.get()); }4 }; }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java
43. Life of a component initialization private void initialize() { this.welderProvider =1DoubleCheck.provider(5 6new Provider<Welder>() { @Override public Welder get()3{ return new Welder( new Wire(), new ProtectiveShield(), flamethrowerProvider.get()); }4 }); }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java
44. Life of a component initialization private void initialize() { this.welderProvider =1DoubleCheck.provider(5 6new Provider<Welder>() { ^ error: [MemoryLeak] this might leak your *entire* component! @Override public Welder get()3{ return new Welder( new Wire(), new ProtectiveShield(), flamethrowerProvider.get()); }4 }); }2 java/dagger/internal/codegen/FrameworkFieldInitializer.java ^ shameless plug for ErrorProne github.com/google/error-prone
45. Life of a component initialization java/dagger/internal/codegen/FrameworkFieldInitializer.java
46. Life of a component initialization private void initialize() { java/dagger/internal/codegen/FrameworkFieldInitializer.java
47. Life of a component initialization private void initialize() { this.wireProvider = Wire_Factory.create(); java/dagger/internal/codegen/FrameworkFieldInitializer.java
48. Life of a component initialization private void initialize() { this.wireProvider = Wire_Factory.create(); this.protectiveShieldProvider =
 ProtectiveShield_Factory.create(); java/dagger/internal/codegen/FrameworkFieldInitializer.java
49. Life of a component initialization private void initialize() { this.wireProvider = Wire_Factory.create(); this.protectiveShieldProvider =
 ProtectiveShield_Factory.create(); this.welderProvider = DoubleChecker.provider(
 Welder_Factory.create(
 wireProvider,
 protectiveShieldProvider,
 flamethrowerProvider)); java/dagger/internal/codegen/FrameworkFieldInitializer.java
50. Life of a component initialization private void initialize() { this.wireProvider = Wire_Factory.create(); this.protectiveShieldProvider =
 ProtectiveShield_Factory.create(); this.welderProvider = DoubleChecker.provider(
 Welder_Factory.create(
 wireProvider,
 protectiveShieldProvider,
 flamethrowerProvider)); } java/dagger/internal/codegen/FrameworkFieldInitializer.java
51. Why does this matter?
52. tl;dr: component initialization is
53. tl;dr: component initialization is s l o w
54. But just how slow is it? Activity component measurements initialization time
55. But just how slow is it? 200ms Activity component measurements initialization time init #1
56. But just how slow is it? 200ms 2 ms Activity component measurements initialization time init #1 init #2+
57. But just how slow is it? 200ms 2 ms 102! Activity component measurements initialization time init #1 init #2+
58. But just how slow is it? 200ms 2 ms 102! Activity component measurements initialization time What is happening here? init #1 init #2+
59. But just how slow is it? 200ms 2 ms 102! Activity component measurements initialization time What is happening here? Answer: class loading init #1 init #2+
60. How can we load fewer classes?
61. How can we load fewer classes? • com.google.dagger:dagger-compiler:2.12
62. How can we load fewer classes? • com.google.dagger:dagger-compiler:2.12 ◦ coming very soon!
63. Dagger 2.12 Bindings Provider form Inlined form java/dagger/internal/codegen/SetBindingExpression.java
64. Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoSet T single() { … } @Provides @ElementsIntoSet Set<T> many() { … } java/dagger/internal/codegen/SetBindingExpression.java
65. Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoSet T single() { … } @Provides @ElementsIntoSet Set<T> many() { … } SetFactory.builder() .add(Single_Factory.create()) .addAll(Many_Factory.create()) .build(); java/dagger/internal/codegen/SetBindingExpression.java
66. Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoSet T single() { … } @Provides @ElementsIntoSet Set<T> many() { … } SetFactory.builder() .add(Single_Factory.create()) .addAll(Many_Factory.create()) .build(); ImmutableSet.builder() .add(single()) .addAll(many()) .build(); java/dagger/internal/codegen/SetBindingExpression.java
67. Dagger 2.12 Bindings Provider form Inlined form java/dagger/internal/codegen/MapBindingExpression.java
68. Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoMap @IntKey(1) V first() { … } @Provides @IntoMap @IntKey(2) V second() { … } java/dagger/internal/codegen/MapBindingExpression.java
69. Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoMap @IntKey(1) V first() { … } @Provides @IntoMap @IntKey(2) V second() { … } MapFactory.builder() .put(1, First_Factory.create()) .put(2, Second_Factory.create()) .build(); java/dagger/internal/codegen/MapBindingExpression.java
70. Dagger 2.12 Bindings Provider form Inlined form @Provides @IntoMap @IntKey(1) V first() { … } @Provides @IntoMap @IntKey(2) V second() { … } MapFactory.builder() .put(1, First_Factory.create()) .put(2, Second_Factory.create()) .build(); ImmutableMap.builder() .put(1, first()) .put(2, second()) .build(); java/dagger/internal/codegen/MapBindingExpression.java
71. Dagger 2.12 Bindings Provider form Inlined form java/dagger/internal/codegen/OptionalBindingExpression.java
72. Dagger 2.12 Bindings Provider form Inlined form @BindsOptionalOf DebugLogger sometimes(); java/dagger/internal/codegen/OptionalBindingExpression.java
73. Dagger 2.12 Bindings Provider form Inlined form @BindsOptionalOf DebugLogger sometimes(); new Provider<Optional<DebugLogger>>() { @Override public Optional<DebugLogger> get() { return Optional.of(debugLoggerProvider.get()); } } java/dagger/internal/codegen/OptionalBindingExpression.java
74. Dagger 2.12 Bindings Provider form Inlined form @BindsOptionalOf DebugLogger sometimes(); new Provider<Optional<DebugLogger>>() { @Override public Optional<DebugLogger> get() { return Optional.of(debugLoggerProvider.get()); } } Optional.of(DebugModule.logger()); java/dagger/internal/codegen/OptionalBindingExpression.java
75. Dagger 2.12 Bindings Provider form Inlined form java/dagger/internal/codegen/ComponentProvisionBindingExpression.java
76. Dagger 2.12 Bindings Provider form Inlined form @Component @Component( interface DatabaseComponent { dependencies = DatabaseComponent.class) Database database(); interface NetworkingComponent { } UsesDatabase usesDatabase(); } java/dagger/internal/codegen/ComponentProvisionBindingExpression.java
77. Dagger 2.12 Bindings Provider form Inlined form @Component @Component( interface DatabaseComponent { dependencies = DatabaseComponent.class) Database database(); interface NetworkingComponent { } UsesDatabase usesDatabase(); } new Provider<Database>() { @Override public Database get() { return databaseComponent.database(); } }; java/dagger/internal/codegen/ComponentProvisionBindingExpression.java
78. Dagger 2.12 Bindings Provider form Inlined form @Component @Component( interface DatabaseComponent { dependencies = DatabaseComponent.class) Database database(); interface NetworkingComponent { } UsesDatabase usesDatabase(); } new Provider<Database>() { @Override public Database get() { return databaseComponent.database(); } }; databaseComponent.database(); java/dagger/internal/codegen/ComponentProvisionBindingExpression.java
79. How can we load fewer classes? • com.google.dagger:dagger-compiler:2.12 ◦ coming very soon!
80. How can we load fewer classes? • com.google.dagger:dagger-compiler:2.12 ◦ coming very soon! • Unnecessary Provider/Lazy usage
81. Don't force Dagger's hand public class DroidconScheduleActivity extends Activity { @Inject Provider<Schedule> scheduleProvider; @Override public void onCreate() { scheduleView.setSchedule(scheduleProvider.get()); } }
82. Don't force Dagger's hand
83. Don't force Dagger's hand If you inject…
84. Don't force Dagger's hand If you inject… || Provider<YourBinding>
85. Don't force Dagger's hand If you inject… || Provider<YourBinding> || Lazy<YourBinding>
86. Don't force Dagger's hand If you inject… || Provider<YourBinding> || Lazy<YourBinding>
87. Don't force Dagger's hand If you inject… || Provider<YourBinding> || Lazy<YourBinding> And
88. Don't force Dagger's hand If you inject… || Provider<YourBinding> || Lazy<YourBinding> And || you always call get() exactly once (especially in the constructor / onCreate())
89. Don't force Dagger's hand If you inject… || Provider<YourBinding> || Lazy<YourBinding> And || you always call get() exactly once (especially in the constructor / onCreate()) || YourBinding is not expensive to create, but you aren't sure if you need it
90. Don't force Dagger's hand If you inject… || Provider<YourBinding> || Lazy<YourBinding> And || you always call get() exactly once (especially in the constructor / onCreate()) || YourBinding is not expensive to create, but you aren't sure if you need it
91. Don't force Dagger's hand If you inject… || Provider<YourBinding> || Lazy<YourBinding> And || you always call get() exactly once (especially in the constructor / onCreate()) || YourBinding is not expensive to create, but you aren't sure if you need it Instead
92. Don't force Dagger's hand If you inject… || Provider<YourBinding> || Lazy<YourBinding> And || you always call get() exactly once (especially in the constructor / onCreate()) || YourBinding is not expensive to create, but you aren't sure if you need it Instead && Simply inject YourBinding with no wrapper type
93. Don't force Dagger's hand If you inject… || Provider<YourBinding> || Lazy<YourBinding> And || you always call get() exactly once (especially in the constructor / onCreate()) || YourBinding is not expensive to create, but you aren't sure if you need it Instead && Simply inject YourBinding with no wrapper type && Profile your code!
94. Don't force Dagger's hand public class DroidconScheduleActivity extends Activity { @Inject Lazy<Schedule> lazySchedule; @Override public void onCreate() { scheduleView.setSchedule(lazySchedule.get()); }1 }2
95. Don't force Dagger's hand public class DroidconScheduleActivity extends Activity { @Inject Lazy<Schedule> lazySchedule; @Inject Lazy<Schedule> lazySchedule2; @Override public void onCreate() { scheduleView.setSchedule(lazySchedule.get()); }1 }2
96. Don't force Dagger's hand public class DroidconScheduleActivity extends Activity { @Inject Lazy<Schedule> lazySchedule; @Inject Lazy<Schedule> lazySchedule2; @Override public void onCreate() { assertThat(lazySchedule.get()); }1 }2
97. Don't force Dagger's hand public class DroidconScheduleActivity extends Activity { @Inject Lazy<Schedule> lazySchedule; @Inject Lazy<Schedule> lazySchedule2; @Override public void onCreate() { assertThat(lazySchedule.get()) .isNotSameAs(lazySchedule2.get()); }1 }2
98. Don't force Dagger's hand @Inject Provider<YourBinding> myProvider; YourBinding[] array = new YourBinding[4]; for (i = 0; i < 4; i++) { array[i] = myProvider.get();2 }1
99. Don't force Dagger's hand @Inject Provider<YourBinding> myProvider; @Inject<YourBinding>yb0; @Inject<YourBinding>yb1; @Inject<YourBinding>yb2; @Inject<YourBinding>yb3; YourBinding[] array = new YourBinding[4]; for (i = 0; i < 4; i++) { array[i] = myProvider.get();2 }1
100. Don't force Dagger's hand @Inject Provider<YourBinding> myProvider; @Inject<YourBinding>yb0; @Inject<YourBinding>yb1; @Inject<YourBinding>yb2; @Inject<YourBinding>yb3; YourBinding[] array = {yb0, yb1, yb2, yb3};
101. Don't force Dagger's hand @Inject<YourBinding>yb0; @Inject<YourBinding>yb1; @Inject<YourBinding>yb2; @Inject<YourBinding>yb3; YourBinding[] array = {yb0, yb1, yb2, yb3};
102. How can we load fewer classes? • com.google.dagger:dagger-compiler:2.12 ◦ coming very soon! • Unnecessary Provider/Lazy usage
103. How can we load fewer classes? • com.google.dagger:dagger-compiler:2.12 ◦ coming very soon! • Unnecessary Provider/Lazy usage • Reconsider scoping decisions
104. Reconsider scoping
105. Reconsider scoping @AnalyticsScope
 class AnalyticsTracker {
106. Reconsider scoping @AnalyticsScope
 class AnalyticsTracker { @Inject AnalyticsTracker(
 UnsyncedAnalyticsQueue queue,
 String flowName,
 ViewToAnalyticsIdTranslator viewTranslator) { … }
107. Reconsider scoping @AnalyticsScope
 class AnalyticsTracker { @Inject AnalyticsTracker(
 UnsyncedAnalyticsQueue queue,
 String flowName,
 ViewToAnalyticsIdTranslator viewTranslator) { … } 
 void trackClick(View view) {
 queue.add(flowName, viewTranslator.translate(view)); }
108. Reconsider scoping @AnalyticsScope
 class AnalyticsTracker { @Inject AnalyticsTracker(
 UnsyncedAnalyticsQueue queue,
 String flowName,
 ViewToAnalyticsIdTranslator viewTranslator) { … } 
 void trackClick(View view) {
 queue.add(flowName, viewTranslator.translate(view)); } 
 void onDetach() { queue.sendAnalyticsToServer(); }
 }A
109. Reconsider scoping @AnalyticsScope class AnalyticsTracker { @Inject AnalyticsTracker( UnsyncedAnalyticsQueue queue, String flowName, ViewToAnalyticsIdTranslator viewTranslator) { … } }A
110. Reconsider scoping @AnalyticsScope class AnalyticsTracker { @Inject AnalyticsTracker( UnsyncedAnalyticsQueue queue, String flowName, ViewToAnalyticsIdTranslator viewTranslator) { … } }A class UnsyncedAnalyticsQueue {}
111. Reconsider scoping class AnalyticsTracker { @Inject AnalyticsTracker( UnsyncedAnalyticsQueue queue, String flowName, ViewToAnalyticsIdTranslator viewTranslator) { … } }A @AnalyticsScope class UnsyncedAnalyticsQueue {}
112. Reconsider scoping @Singleton @Component(modules = ExecutorModule.class) interface NetworkingComponent {Q…Z} @Module abstract class ExecutorModule { @Provides @Singleton @Background Executor provideBackgroundExecutor() { return Executors.newCachedThreadPool(4); } }
113. Reconsider scoping @Singleton @Component(modules = ExecutorModule.class) interface NetworkingComponent { Q// …Z }R
114. Reconsider scoping @Singleton @Component interface NetworkingComponent { // …Z 1 }R2
115. Reconsider scoping @Singleton @Component interface NetworkingComponent { // … 1@Component.Builder interface Builder { @BindsInstance Builder executor(Executor e); NetworkingComponent build(); } }R
116. How can we load fewer classes? • com.google.dagger:dagger-compiler:2.12 ◦ coming very soon! • Unnecessary Provider/Lazy usage • Reconsider scoping decisions
117. How can we load fewer classes? • com.google.dagger:dagger-compiler:2.12 ◦ coming very soon! • Unnecessary Provider/Lazy usage • Reconsider scoping decisions • Suggest better codegen strategies ◦ github.com/google/dagger/issues
118. Dagger on Android Stop making me think about injection
119. Dagger on Android public class LoginActivity extends Activity { @Inject OAuthClient oauth; @Inject PasswordEncrypter encrypter; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ((DroidconApp) getApplication()) .getComponent() .inject(this); } }
120. Dagger on Android public class DroidconApp extends Application { private DroidconComponent component; public DroidconComponent getComponent() { if (component == null) { component = DaggerDroidconComponent.create(); } return component; } }
121. dagger.android public class LoginActivity extends DaggerActivity { @Inject OAuthClient oauth; @Inject PasswordEncrypter encrypter; } public class DroidconApp extends DaggerApplication {} @Module interface LoginModule { @ContributesAndroidInjector LoginActivity configureLoginActivityInjection(); }
122. dagger.android • DaggerActivity • DaggerFragment • DaggerService + DaggerIntentService • DaggerBroadcastReceiver • DaggerApplication • DaggerAppCompatActivity • dagger.android.support.DaggerFragment • @ContributesAndroidInjector
123. dagger.android under the hood @ContributesAndroidInjector(modules = LoginSpecificModule.class) LoginActivity loginActivity(); @Subcomponent(modules = LoginSpecificModule.class) interface LoginActivitySubcomponent extends AndroidInjector<LoginActivity> { @Subcomponent.Builder abstract class Builder extends AndroidInjector.Builder<LoginActivity> {} }
124. Faster builds w/ Dagger
125. Compile as little as possible • When you have a hammer, everything looks like a @Subcomponent ◦ but subcomponents require compilation at the root! • Break up compilation where possible ◦ gradle users: make lots of modules ◦ bazel users: split up java_librarys
126. Compile as little as possible
127. Compile as little as possible @Component(modules = NetworkingModule.class)
 interface NetworkingComponent {
 OkHttpClient httpClient();
 }
128. Compile as little as possible @Component(modules = NetworkingModule.class)
 interface NetworkingComponent {
 OkHttpClient httpClient();
 }
129. Compile as little as possible @Component(modules = NetworkingModule.class)
 interface NetworkingComponent {
 OkHttpClient httpClient();
 } 
 @Component(dependencies = NetworkingComponent.class)
 interface AppComponent {
 ApiService apiService();
 }
130. Compile as little as possible @Component(modules = NetworkingModule.class)
 interface NetworkingComponent {
 OkHttpClient httpClient();
 } 
 @Component(dependencies = NetworkingComponent.class)
 interface AppComponent {
 ApiService apiService();
 }
131. Compile as little as possible @Component(modules = NetworkingModule.class)
 interface NetworkingComponent {
 OkHttpClient httpClient();
 } 
 @Component(dependencies = NetworkingComponent.class)
 interface AppComponent {
 ApiService apiService();
 } class ApiService {
 @Inject ApiService(OkHttpClient httpClient) { … }
 }
132. Compile as little as possible @Component(modules = NetworkingModule.class)
 interface NetworkingComponent {
 OkHttpClient httpClient();
 } 
 @Component(dependencies = NetworkingComponent.class)
 interface AppComponent {
 ApiService apiService();
 } class ApiService {
 @Inject ApiService(OkHttpClient httpClient) { … }
 }
133. Compile as little as possible @Component(modules = NetworkingModule.class)
 interface NetworkingComponent {
 OkHttpClient httpClient();
 } 
 @Component(dependencies = NetworkingComponent.class)
 interface AppComponent {
 ApiService apiService();
 } class ApiService {
 @Inject ApiService(OkHttpClient httpClient) { … }
 } separate compilations!
134. Compile as little as possible public final class DaggerAppComponent implements AppComponent { private NetworkingComponent networkComponentDependency; @Override public void ApiService apiService() { return new ApiService(networkComponentDependency.httpClient()); } }
135. Summarize: Read the generated code
136. Questions? ronsh@google @rdshapiro