Listed below are the steps I did and my key learnings to transform my Android Information app to make use of hilt dependency injection
This text was initially printed at vtsen.hashnode.dev on July 16, 2022.
So I adopted the steps in Tips on how to Implement Hilt in Android App? article to transform the Android Information app to make use of Hilt Dependency Injection. The distinction in earlier article is it does not cowl the View Mannequin dependency injection.
1. Add Dependencies and @HiltAndroidApp
The preliminary setup steps are precisely the identical as the next:
2. Add @HiltViewModel and @Inject Constructor
To ensure that Hilt to create MainViewModel, you have to annotate the category with @HiltViewModel. @Inject constructor can be used to inform Hilt how the dependencies will be created.
@HiltViewModel
class MainViewModel
@Inject constructor(
personal val repository: ArticlesRepository,
) : ViewModel() {
...
}
I additionally use @Inject Constructor on the SqlArticlesRepository.
class SqlArticlesRepository @Inject constructor(
personal val database: ArticlesDatabase,
personal val webService: WebService,
) : ArticlesRepository {
...
}
3. Add @Gives and @Binds
To create the dependencies, we use both @Gives and @Binds. @Gives is used to create ArticlesDatabase and WebService situations.
@Module
@InstallIn(SingletonComponent::class)
object DatabaseModule {
@Gives
@Singleton
enjoyable provideDatabase(@ApplicationContext appContext: Context): ArticlesDatabase {
return Room.databaseBuilder(
appContext,
ArticlesDatabase::class.java,
"articles.db",
)
.fallbackToDestructiveMigration()
.construct()
}
}
@Module
@InstallIn(SingletonComponent::class)
object WebServiceModule {
@Gives
@Singleton
enjoyable provideWebService(): WebService {
return WebService()
}
}
@Binds is used to create the implementation of ArticlesRepository interface.
@Module
@InstallIn(SingletonComponent::class)
summary class RepositoryModule {
@Binds
@Singleton
summary enjoyable bindArticlesRepository(impl: SqlArticlesRepository): ArticlesRepository
}
4. Name hiltViewModel() Composable
Now it’s performed! All guide creations under in MainActivity will be eliminated.
personal val repository by lazy {
SqlArticlesRepository(
ArticlesDatabase.getInstance(software),
WebService(),
)
}
personal val homeViewModel by viewModels<MainViewModel> {
MainViewModelFactory(repository)
}
The MainViewModel creation will be performed by calling the hiltViewModel() composable perform, which generates all the mandatory dependencies.
For instance, exchange this MainScreen composable perform
MainScreen(homeViewModel, useSystemUIController = true)
with
MainScreen(viewModel = hiltViewModel(), useSystemUIController = true)
The database creation under can be eliminated because it has been offered by hilt @Gives above.
companion object {
@Risky
personal lateinit var occasion: ArticlesDatabase
enjoyable getInstance(context: Context): ArticlesDatabase {
synchronized(this) {
if (!::occasion.isInitialized) {
occasion = Room.databaseBuilder(
context.applicationContext,
ArticlesDatabase::class.java,
"articles.db")
.fallbackToDestructiveMigration()
.construct()
}
return occasion
}
}
}
This MainViewModelFactory can be eliminated since this has been taken care by @HiltViewModel.
@Suppress("UNCHECKED_CAST")
class MainViewModelFactory(personal val repository: ArticlesRepository)
: ViewModelProvider.NewInstanceFactory() {
override enjoyable <T : ViewModel> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(MainViewModel::class.java)) {
return MainViewModel(repository) as T
}
throw IllegalArgumentException("Unknown ViewModel class")
}
}
Conclusion
All my put in Hilt modules are in SingletonComponent scope. If I alter my put in module to a different part, for instance ViewModelComponent or ActivityComponent, it fails to compile, and I do not know repair it I assume that’s my subsequent step to mess around with this Hilt.
Sure, I nonetheless don’t love Hilt. Name me grand pa, I nonetheless desire guide dependency inject like this one:
