Hilt: A Dependency Injection Library for Android
If you are an Android developer, you might have heard of Hilt, a new library that simplifies dependency injection (DI) in your apps. But what is Hilt and why should you use it?
Hilt is a dependency injection library for Android that reduces the boilerplate of doing manual DI in your project. Dependency injection is a technique that allows you to decouple the creation and usage of objects in your code, making it easier to test and maintain. However, doing manual DI requires you to write a lot of repetitive and error-prone code to construct and provide dependencies to your classes.
Hilt provides a standard way to use DI in your app by providing containers for every Android class in your project and managing their lifecycles automatically. Hilt is built on top of the popular DI library Dagger to benefit from the compile-time correctness, runtime performance, scalability, and Android Studio support that Dagger provides.
To use Hilt in your app, you need to follow these steps:
- Add the Hilt dependencies and plugins to your project’s build.gradle files.
- Annotate your Application class with @HiltAndroidApp to trigger Hilt’s code generation and create an application-level container.
- Annotate your Android classes, such as Activity, Fragment, ViewModel, Service, etc., with @AndroidEntryPoint to enable field injection and access the application-level container.
- Define your dependencies as classes or interfaces annotated with @Inject, @Binds, or @Provides, and group them into modules annotated with @Module and @InstallIn.
- Use constructor injection or field injection to inject your dependencies into your classes.
For example, you can create a UserRepository class that depends on a UserService interface, and provide them using Hilt:
// A dependency that provides user data from a remote source
interface UserService {
fun getUser(id: String): User
}// A class that depends on UserService
class UserRepository @Inject constructor(
private val userService: UserService
) {
fun getUser(id: String): User {
return userService.getUser(id)
}
}// A module that provides UserService
@Module
@InstallIn(SingletonComponent::class)
object NetworkModule { @Provides
fun provideUserService(): UserService {
return Retrofit.Builder()
.baseUrl("https://example.com")
.build()
.create(UserService::class.java)
}
}
Then, you can inject UserRepository into your ViewModel using constructor injection:
@HiltViewModel
class UserViewModel @Inject constructor(
private val userRepository: UserRepository
) : ViewModel() { fun getUser(id: String): User {
return userRepository.getUser(id)
}
}And you can inject UserViewModel into your Fragment using field injection:
@AndroidEntryPoint
class UserFragment : Fragment() {// Inject UserViewModel into the fragment
@Inject lateinit var userViewModel: UserViewModel override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
// Use UserViewModel to get user data
val user = userViewModel.getUser("123")
// Update UI with user data
...
}
}
If you want to learn more about Hilt and how to use it to simplify DI in your app, you can check out the following resources:
Hilt is a powerful and easy-to-use library that makes DI a breeze on Android. It lets you focus on what matters most: your app’s functionality and user experience. With Hilt, you can build better apps faster and easier. So what are you waiting for? Start using Hilt today!
