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Version: 4.2

Android Context & Qualifiers

This guide covers Android-specific qualifier patterns, particularly around Context handling.

info

For general qualifier concepts (named, type-safe, enums, JSR-330), see Qualifiers.

Android Context - No Qualifiers Needed​

Unlike Hilt, Koin automatically provides the Android Context without requiring qualifiers.

Koin's Context Resolution​

val androidModule = module {
    // Context is automatically available
    single {
        SharedPreferences(
            androidContext()  // Application context automatically provided
        )
    }

    single {
        NotificationManager(
            androidContext().getSystemService(Context.NOTIFICATION_SERVICE)
        )
    }
}

No @ApplicationContext or @ActivityContext​

In Hilt, you need:

// Hilt requires explicit qualifiers
class MyRepository @Inject constructor(
    @ApplicationContext private val context: Context
)

In Koin, it's automatic:

class MyRepository(
    private val context: Context  // Just use Context
)

val appModule = module {
    single { MyRepository(androidContext()) }
}
info

Koin Advantage: The androidContext() function always provides the Application context. No qualifiers needed to distinguish between Application and Activity contexts.

When You Need Activity Context​

For cases where you need Activity context, don't inject it - use it directly:

class ScreenMetrics(private val activity: Activity) {
    fun getScreenSize(): Point {
        val display = activity.windowManager.defaultDisplay
        return Point().also { display.getSize(it) }
    }
}

// Don't define in modules - create directly in Activity
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val metrics = ScreenMetrics(this)  // Activity context used directly
    }
}
warning

Best Practice: Avoid injecting Activity context into long-lived objects. It causes memory leaks. Use Application context (androidContext()) for dependencies that outlive an Activity.

Qualified Android Dependencies​

When you need multiple configurations of Android-specific dependencies:

val databaseModule = module {
    single(named("user_db")) {
        Room.databaseBuilder(
            androidContext(),
            UserDatabase::class.java,
            "user-database"
        ).build()
    }

    single(named("cache_db")) {
        Room.databaseBuilder(
            androidContext(),
            CacheDatabase::class.java,
            "cache-database"
        ).build()
    }
}

Next Steps​