Hilt the DI ground running

Slide 1

Slide 1 text

Hilt the DI ground running Moyinoluwa Adeyemi @moyheen

Slide 2

Slide 2 text

What is Dependency Injection?

Slide 3

Slide 3 text

What is Dependency Injection? “dependency injection is a technique in which an object receives other objects that it depends on” According to good ol’ wikipedia

Slide 4

Slide 4 text

Dependency Injection

Slide 5

Slide 5 text

Dependency Injection

Slide 6

Slide 6 text

No Dependency Injection class RoboGardener { fun waterPlant() { val waterSource = WaterSource() waterSource.dispenseWater() } }

Slide 7

Slide 7 text

Dependency Injection - Constructor class RoboGardener(private val waterSource: WaterSource) { fun waterPlant() { waterSource.dispenseWater() } }

Slide 8

Slide 8 text

Dependency Injection - Constructor class RoboGardener(private val waterSource: WaterSource) { fun waterPlant() { waterSource.dispenseWater() } } fun main() { val roboGardener = RoboGardener(CupOfWater()) roboGardener.waterPlant() }

Slide 9

Slide 9 text

Dependency Injection - Setter class RoboGardener { lateinit var waterSource: WaterSource fun waterPlant() { waterSource.dispenseWater() } }

Slide 10

Slide 10 text

Dependency Injection - Setter class RoboGardener { lateinit var waterSource: WaterSource fun waterPlant() { waterSource.dispenseWater() } } fun main() { val roboGardener = RoboGardener() roboGardener.waterSource = WateringCan() roboGardener.waterPlant() }

Slide 11

Slide 11 text

Dependency Injection - Interface interface WaterSourceManager { fun provideWaterSource(waterSource: WaterSource) }

Slide 12

Slide 12 text

Slide 13

Slide 13 text

Dependency Injection - Interface interface WaterSourceManager { fun provideWaterSource(waterSource: WaterSource) } class RoboGardener() : WaterSourceManager { private lateinit var waterSource: WaterSource override fun provideWaterSource(waterSource: WaterSource) { this.waterSource = waterSource } fun waterPlant() { waterSource.dispenseWater() } } fun main() { val roboGardener = RoboGardener() roboGardener.provideWaterSource(Hose()) roboGardener.waterPlant() }

Slide 14

Slide 14 text

RoboGardener WaterSource Dependency Injection - Graph

Slide 15

Slide 15 text

Service Locators

Slide 16

Slide 16 text

Service Locators class RoboGardener { fun waterPlant() { val waterSource = CupOfWater() waterSource.dispenseWater() } }

Slide 17

Slide 17 text

class RoboGardener { fun waterPlant() { val waterSource = ServiceLocator.getInstance.findWaterSource() waterSource.dispenseWater() } } Service Locators

Slide 18

Slide 18 text

No increase in app size Manual Dependency Injection

Slide 19

Slide 19 text

Manual Dependency Injection No increase in app size Low Learning Curve

Slide 20

Slide 20 text

High maintenance costs Manual Dependency Injection Low Learning Curve No increase in app size ♀

Slide 21

Slide 21 text

Dependency Injection - Dagger Dagger Code generation Steep learning curve For Java or Kotlin developers Useful for large projects

Slide 22

Slide 22 text

Dependency Injection - Hilt What is different?

Slide 23

Slide 23 text

Dependency Injection - Hilt Low Learning Curve

Slide 24

Slide 24 text

Dependency Injection - Hilt Low Learning Curve Free Lifecycle Management ♻

Slide 25

Slide 25 text

Dependency Injection - Hilt Low Learning Curve Free Lifecycle Management ♻ Co-exist with Dagger ♂

Slide 26

Slide 26 text

Dependency Injection - Hilt Usage - Annotations

Slide 27

Slide 27 text

@HiltAndroidApp class HiltSampleApplication : Application() @HiltAndroidApp

Slide 28

Slide 28 text

@AndroidEntryPoint class MainActivity : AppCompatActivity() { @Inject lateinit var imageLoader: ImageLoader private val viewModel: HiltSampleViewModel by viewModels() ... @AndroidEntryPoint

Slide 29

Slide 29 text

Activity imageLoader viewModel @AndroidEntryPoint

Slide 30

Slide 30 text

@Module @InstallIn(ApplicationComponent::class) abstract class AppModule @InstallIn

Slide 31

Slide 31 text

@Module @InstallIn(ApplicationComponent::class) abstract class AppModule { @Binds abstract fun bindImageLoader(imageLoader: GlideImageLoader): ImageLoader ... } @InstallIn

Slide 32

Slide 32 text

@Module @InstallIn(ApplicationComponent::class) object NetworkModule { @Provides fun providesMoshi(): Moshi = Moshi.Builder() .build() ... @InstallIn

Slide 33

Slide 33 text

class HiltSampleViewModel @ViewModelInject constructor( private val hiltSampleRepository: HiltSampleRepository ) : ViewModel() { ... ViewModels - @ViewModelInject

Slide 34

Slide 34 text

ViewModel repository ViewModels - @ViewModelInject Activity imageLoader viewModel

Slide 35

Slide 35 text

@AndroidEntryPoint @AndroidEntryPoint class MainActivity : AppCompatActivity() { @Inject lateinit var imageLoader: ImageLoader private val viewModel: HiltSampleViewModel by viewModels() ...

Slide 36

Slide 36 text

@EntryPoint - Interface @EntryPoint @InstallIn(ApplicationComponent::class) interface ImageFeatureModule { fun imageLoader(): ImageLoader }

Slide 37

Slide 37 text

@EntryPoint - Dependency retrieval val imageLoader = EntryPoints .get(applicationContext, ImageFeatureModule::class.java) .imageLoader()

Slide 38

Slide 38 text

@EntryPoint - Interface retrieval EntryPointAccessors.fromApplication( applicationContext, ImageFeatureModule::class.java )

Slide 39

Slide 39 text

Dependency Injection - Hilt Usage - Scoping

Slide 40

Slide 40 text

https://developer.android.com/training/dependency-injection/hilt-android#component-scopes Scoping

Slide 41

Slide 41 text

https://dagger.dev/hilt/component-hierarchy.svg Scoping - Hierarchy

Slide 42

Slide 42 text

Scoping - Unscoped bindings @Module @InstallIn(ApplicationComponent::class) abstract class AppModule { @Binds abstract fun bindImageLoader(imageLoader: GlideImageLoader): ImageLoader ...

Slide 43

Slide 43 text

Scoping - Scoped bindings @Module @InstallIn(ApplicationComponent::class) abstract class AppModule { @Singleton @Binds abstract fun bindImageLoader(imageLoader: GlideImageLoader): ImageLoader ... ✅

Slide 44

Slide 44 text

Scoping - Scoped bindings @Module @InstallIn(ApplicationComponent::class) abstract class AppModule { @ActivityRetainedScoped @Binds abstract fun bindImageLoader(imageLoader: GlideImageLoader): ImageLoader ... ❌

Slide 45

Slide 45 text

Scoping - Scoped bindings

Slide 46

Slide 46 text

class HiltSampleViewModel @ViewModelInject constructor( private val hiltSampleRepository: HiltSampleRepository ) : ViewModel() { ... ActivityRetainedComponent Scoping - ViewModel bindings

Slide 47

Slide 47 text

Scoping - Predeﬁned qualiﬁers @ActivityContext - Activity Context binding @ApplicationContext - Application Context binding

Slide 48

Slide 48 text

Scoping - Predeﬁned qualiﬁers class HiltSampleRepositoryImpl @Inject constructor( @ActivityContext private val context: Context, private val hiltSampleService: HiltSampleService ) : HiltSampleRepository {

Slide 49

Slide 49 text

Scoping - Recommendation “only scope the binding if it’s required for the correctness of the code”

Slide 50

Slide 50 text

Dependency Injection - Hilt Usage - Multi-module apps

Slide 51

Slide 51 text

Multi-module apps - Gradle modules Regular gradle modules? ✅

Slide 52

Slide 52 text

Multi-module apps - Feature modules Feature Modules?

Slide 53

Slide 53 text

Multi-module apps - Feature modules “Hilt cannot process annotations in feature modules. You must use Dagger to perform dependency injection in your feature modules” Hilt + Dagger

Slide 54

Slide 54 text

Multi-module apps - Feature modules 1. Install an Entry Point in the Application Component from the app module

Slide 55

Slide 55 text

Multi-module apps - Feature modules 1. Install an Entry Point in the Application Component from the app module @EntryPoint @InstallIn(ApplicationComponent::class) interface ImageFeatureModule { fun imageLoader(): ImageLoader }

Slide 56

Slide 56 text

Multi-module apps - Feature modules 2. In the feature module, create a regular dagger component

Slide 57

Slide 57 text

Multi-module apps - Feature modules 2. In the feature module, create a regular dagger component @Component(dependencies = [ImageFeatureModule::class]) interface ImageFeatureComponent { fun inject(activity: ImageFeatureModuleActivity) @Component.Builder interface Builder { fun dependencies(imageFeatureModule: ImageFeatureModule): Builder fun build(): ImageFeatureComponent } }

Slide 58

Slide 58 text

Multi-module apps - Feature modules 3. Inject the dependency in the feature module

Slide 59

Slide 59 text

Multi-module apps - Feature modules 3. Inject the dependency in the feature module class ImageFeatureModuleActivity : AppCompatActivity() { @Inject lateinit var imageLoader: ImageLoader @AndroidEntryPoint

Slide 60

Slide 60 text

Multi-module apps - Feature modules 3. Inject the dependency in the feature module ... override fun onCreate(savedInstanceState: Bundle?) { DaggerImageFeatureComponent.builder() .dependencies( EntryPointAccessors.fromApplication( applicationContext, ImageFeatureModule::class.java ) ) .build() .inject(this)

Slide 61

Slide 61 text

Slide 62

Slide 62 text

Dependency Injection - Migration Dagger Android -> Hilt

Slide 63

Slide 63 text

Migration - build.gradle

Slide 64

Slide 64 text

Migration - app/build.gradle

Slide 65

Slide 65 text

Migration - app/build.gradle

Slide 66

Slide 66 text

Migration - Application

Slide 67

Slide 67 text

Migration - Hilt_HiltSampleApplication.java (generated)

Slide 68

Slide 68 text

Migration - ViewModel

Slide 69

Slide 69 text

Migration - HiltSampleViewModel_AssistedFactory.java (generated)

Slide 70

Slide 70 text

Migration - HiltSampleViewModel_HiltModule.java (generated)

Slide 71

Slide 71 text

Migration - MainActivity

Slide 72

Slide 72 text

Migration - Hilt_MainActivity.java (generated)

Slide 73

Slide 73 text

Migration - Hilt_MainActivity.java (generated)

Slide 74

Slide 74 text

Migration - Modules

Slide 75

Slide 75 text

Migration - ViewModelFactory, ViewModelKey

Slide 76

Slide 76 text

Migration - HiltSampleApplication_HiltComponents.java (generated)

Slide 77

Slide 77 text

Resources ● Dependency injection with Hilt ● Dagger Hilt ● Using Hilt in your Android app Codelab ● Migrating your Dagger app to Hilt Codelab ● Scoping in Android and Hilt. Scoping an object A to another object B… | by Manuel Vivo | Android Developers ● Hilt in multi-module apps ● https://github.com/moyheen/HiltSampleApplication ● Image by Gerd Altmann from Pixabay

Slide 78

Slide 78 text

Thank You! Moyinoluwa Adeyemi @moyheen