DataStore preferences

Hub › Android › Advanced › DataStore preferences

Goal

Replace SharedPreferences with Jetpack DataStore for type-safe, coroutine-based key-value storage. Persist user preferences like theme toggle and sort order.

Prerequisites

• Firebase Authentication

Why DataStore

SharedPreferences has several problems: synchronous disk I/O on the main thread, no type safety, and no reactive observation. DataStore fixes all three with a Flow-based API and automatic data migration.

Gradle

dependencies {
    implementation("androidx.datastore:datastore-preferences:1.1.2")
}

Preferences DataStore

Create UserPreferences.kt:

import android.content.Context
import androidx.datastore.preferences.core.booleanPreferencesKey
import androidx.datastore.preferences.core.edit
import androidx.datastore.preferences.preferencesDataStore
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.map

private val Context.dataStore by preferencesDataStore(name = "user_prefs")

class UserPreferences(private val context: Context) {

    private object Keys {
        val DARK_MODE = booleanPreferencesKey("dark_mode")
        val SORT_ASCENDING = booleanPreferencesKey("sort_ascending")
    }

    val darkMode: Flow<Boolean> = context.dataStore.data.map { prefs ->
        prefs[Keys.DARK_MODE] ?: false
    }

    val sortAscending: Flow<Boolean> = context.dataStore.data.map { prefs ->
        prefs[Keys.SORT_ASCENDING] ?: true
    }

    suspend fun setDarkMode(enabled: Boolean) {
        context.dataStore.edit { prefs ->
            prefs[Keys.DARK_MODE] = enabled
        }
    }

    suspend fun setSortAscending(ascending: Boolean) {
        context.dataStore.edit { prefs ->
            prefs[Keys.SORT_ASCENDING] = ascending
        }
    }
}

Wire with Hilt

@Module
@InstallIn(SingletonComponent::class)
object PreferencesModule {
    @Provides @Singleton
    fun provideUserPreferences(app: Application): UserPreferences =
        UserPreferences(app)
}

Use in ViewModel

@HiltViewModel
class SettingsViewModel @Inject constructor(
    private val preferences: UserPreferences
) : ViewModel() {

    val darkMode: StateFlow<Boolean> = preferences.darkMode
        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5000), false)

    fun toggleDarkMode() = viewModelScope.launch {
        val current = preferences.darkMode.first()
        preferences.setDarkMode(!current)
    }
}

Checkpoint

# Run app, navigate to settings
# Toggle dark mode → UI switches immediately
# Kill and restart → preference persists

Next: WorkManager — background data sync and periodic work.