Android DataStore: Calling Context.createDataStore from Java

Question

I'm trying to implement the new typed DataStore API in Java and I'm having some issues. All the documentation seems to be in Kotlin only and trying to create a new data store is not as straight forward from the Java side it seems.

Calling DataStoreFactoryKt.createDataStore() from Java requires me to provide all the arguments including the ones with default values in the Kotlin implementation. There doesnt seem to be any @JvmOverloads annotation for that function, resulting in my predicament.

fun <T> Context.createDataStore(
    fileName: String,
    serializer: Serializer<T>,
    corruptionHandler: ReplaceFileCorruptionHandler<T>? = null,
    migrations: List<DataMigration<T>> = listOf(),
    scope: CoroutineScope = CoroutineScope(Dispatchers.IO + SupervisorJob())
): DataStore<T> =
    DataStoreFactory.create(
        produceFile = { File(this.filesDir, "datastore/$fileName") },
        serializer = serializer,
        corruptionHandler = corruptionHandler,
        migrations = migrations,
        scope = scope
)

What's the better way around this, if there is any? Or is the Data Store api simple designed to be used with Kotlin only? I have no idea how I would go about providing a CoroutineScope argument from Java.

Answer 1

After updating dataStore dependency to '1.0.0-alpha08' as below.

// DataStore
implementation "androidx.datastore:datastore-preferences:1.0.0-alpha08"

You can have preferences implementation as follow:

private val Context.dataStore by preferencesDataStore("app_preferences")

After that if you like create some preference key:

private object Keys {
    val HIDE_VISITED = booleanPreferencesKey("hide_visited")
}

other options can be stringPreferencesKey, intPreferencesKey, etc.

Saving value example:

context.dataStore.edit { prefs -> prefs[Keys.HIDE_VISITED] = hideVisited }

Reading saved value example:

val hideVisited = preferences[Keys.HIDE_VISITED] ?: false

Answer 2

You need to add to your Grade build file the dependency for DataStore preferences:

implementation "androidx.datastore:datastore-preferences:1.0.0-alpha04"

and not the one for Types, that way you will be able to resolve the androidx.datastore.preferences.Context.createDataStore method that you are expecting:

public fun Context.createDataStore(
    name: String,
    corruptionHandler: ReplaceFileCorruptionHandler<Preferences>? = null,
    migrations: List<DataMigration<Preferences>> = listOf(),
    scope: CoroutineScope = CoroutineScope(Dispatchers.IO + SupervisorJob())
): DataStore<Preferences> =
    PreferenceDataStoreFactory.create(
        corruptionHandler = corruptionHandler,
        migrations = migrations,
        scope = scope
    ) {
        File(this.filesDir, "datastore/$name.preferences_pb")
    }