ArjunGupta08 / Hilt

Dependency injection with Hilt

Hilt Intro

Project SetUp

build.gradle ( Module Level )

kotlin("kapt")
id("com.google.dagger.hilt.android")

// Hilt
implementation("com.google.dagger:hilt-android:2.51")
kapt("com.google.dagger:hilt-android-compiler:2.51")

// Allow references to generated code
kapt {
    correctErrorTypes = true
}

build.gradle ( Project Level )

id("com.google.dagger.hilt.android") version "2.51" apply false

@HiltAndroidApp

Hilt provides an easy way to inject dependencies. By just having an application class annotated with @HiltAndroidApp - dependency injection is done for you automatically. Fields marked with @Inject are injected automatically by Hilt. Don't forget to mention this application class in your manifest file.

@AndroidEntryPoint

@AndroidEntryPoint is another annotation that is required on Android classes like Activity, Fragment, Views that requires object to be injected. All the code generation is done by Hilt i.e. behind the scene Hilt generates Dagger2 code for you using these annotations.

@Provides with @InstallIn

@Provides annotation along with @InstallIn annotation in HILT. These annotations are required when you cannot use @Inject annotation on the constructor of classes or for scenarios where you have interfaces or abstract classes or classes that requires some patterns for object creation. For instance, room database requires builder pattern, for this we need modules.

Learn about predefined set of components for each android class in Hilt. i.e. Singleton Component, Activity Component, Fragment Component in Hilt

@Binds

When you want to bind implementation to an interface, we use @Binds annotation. You can use @Provides annotation for interfaces where Hilt is unable to create the object itself i.e. required class is not annotated with @Inject.

Qualifiers

It is like a tag that is attached to different implementation. Whenever you request object from Hilt, you pass the tag i.e. the qualifier along with the requested object. For this we have default @Named annotation or we can create custom qualifiers.