Mode d’emploi
- Copiez la commande et examinez le paquet avant de l’installer dans votre environnement agent.
- Consultez le document original pour les outils, identifiants et environnements requis.
- Décrivez les entrées et le livrable souhaité ; comparez la sortie aux sources.
npx skills add https://github.com/rcosteira79/android-skills --skill datastoreAvant de commencer
- L’installation n’inclut ni abonnement au modèle, ni quota API, ni accès aux fichiers.
- Étoiles et installations reflètent l’activité, pas un test indépendant de qualité ou de sécurité.
Rendu depuis le dépôt source en conservant titres, exemples, code, tableaux, liens et images.
Jetpack DataStore for Android and KMP
Reactive coroutine-based key-value / typed storage; the same androidx.datastore:datastore-preferences-core runs on Android, iOS, and JVM — only the file-path producer is platform-specific. (Web support is 1.3.0-alpha only, and it's sessionStorage/OPFS-backed there, not file-path-based.) This reference covers the storage-choice call plus the two error/path traps, not the basics of Preferences keys, edit { }, or Serializer<T>. Adapted from Meet-Miyani/compose-skill; MIT. Related: android-skills:android-data-layer, android-skills:kmp-boundaries, android-skills:kotlin-flows.
Preferences vs Typed vs Room
| Need | Storage |
|---|---|
| Key-value flags (theme, locale, onboarding done) | Preferences DataStore |
| One typed object, many related fields, schema evolution | Typed DataStore + Serializer<T> |
Relational data, indexes, WHERE / JOIN, >100 entries, paging | Room |
| Payloads above ~50KB per write | Room / filesystem — DataStore rewrites the whole file on every edit |
Rule of thumb: if a WHERE clause would be useful, use Room.
The two traps
`.catch` must match `IOException` specifically — never a broad `catch`. A bare catch { emit(emptyPreferences()) } swallows CancellationException (breaking structured concurrency) and hides serializer/corruption errors behind a silent empty state.
val settings: Flow<UserSettings> = dataStore.data
.catch { e -> if (e is IOException) emit(emptyPreferences()) else throw e }
.map { p -> UserSettings(p[Keys.DARK_MODE] ?: false, p[Keys.LOCALE] ?: "en") }Typed-DataStore corruption recovery triggers on `CorruptionException`, NOT `IOException`. The serializer's readFrom must wrap parse failures in CorruptionException, and the store needs a ReplaceFileCorruptionHandler — without it, one corrupt file makes every read fail permanently.
object AppSettingsSerializer : Serializer<AppSettings> {
override val defaultValue = AppSettings()
override suspend fun readFrom(input: InputStream): AppSettings =
try { Json.decodeFromString(input.readBytes().decodeToString()) }
catch (e: SerializationException) { throw CorruptionException("Cannot read AppSettings", e) }
override suspend fun writeTo(t: AppSettings, output: OutputStream) =
output.write(Json.encodeToString(t).encodeToByteArray())
}
val store = DataStoreFactory.create(
serializer = AppSettingsSerializer,
corruptionHandler = ReplaceFileCorruptionHandler { AppSettings() },
produceFile = { File(context.filesDir, "app_settings.json") },
)KMP factory — per-platform path (not the temp dir)
// commonMain
fun createPreferencesDataStore(producePath: () -> String): DataStore<Preferences> =
PreferenceDataStoreFactory.createWithPath(produceFile = { producePath().toPath() })
// android: context.filesDir.resolve(PREFS_FILE).absolutePath
// ios: NSDocumentDirectory via NSFileManager
// jvm: File(System.getProperty("user.home"), ".myapp") — NOT java.io.tmpdir (the OS may wipe it on reboot)(In a composable, never runBlocking on DataStore — it parks the main thread on disk I/O, risking an ANR, and re-runs every recomposition. Expose a StateFlow and collect with collectAsStateWithLifecycle.)
