Jetpack DataStore is the modern replacement for SharedPreferences, offering Coroutines support and type safety. But migrating existing users' data without causing a "first-launch" reset is the biggest technical challenge.
The SharedPrefs Migration Tool
Google provides a built-in migration handler. You don't have to manually read and write strings. You just provide the name of your old preferences file, and DataStore handles the mapping.
val Context.dataStore by preferencesDataStore(
name = "settings",
produceMigrations = { context ->
listOf(SharedPreferencesMigration(context, "old_prefs_name"))
}
)
Handling Async Timing
Unlike SharedPreferences, DataStore is 100% asynchronous. If you try to read a value on the main thread during app startup, you'll block the UI or get an empty result. Always collect the DataStore flow within a coroutine scope.
val userFlow: Flow<UserPreferences> = dataStore.data
.catch { exception ->
if (exception is IOException) emit(emptyPreferences())
else throw exception
}
The Golden Rule
Once the migration runs, SharedPreferences are not automatically deleted. However, DataStore will only run the migration logic once. Ensure your logic doesn't depend on both systems simultaneously, as it will lead to conflicting states.
Summary
Use the built-in migration tool and embrace the asynchronous Flow. Your users will never know they switched systems, but your code will be much cleaner!