lifecycle aware sp listener #lifecycle #flow #shared_preferences

ObservableSharedPreferences.kt

    fun <T> SharedPreferences.observeKey(key: String, default: T): Flow<T> {
        return callbackFlow {
            send(getItem(key, default))

            val listener = SharedPreferences.OnSharedPreferenceChangeListener { _, k ->
                if (key == k) {
                    offer(getItem(key, default))
                }
            }

            registerOnSharedPreferenceChangeListener(listener)
            awaitClose {
                unregisterOnSharedPreferenceChangeListener(listener)
            }
        }
    }

    fun <T> SharedPreferences.getItem(key: String, default: T): T {
        @Suppress("UNCHECKED_CAST")
        return when (default) {
            is String -> getString(key, default) as T
            is Int -> getInt(key, default) as T
            is Long -> getLong(key, default) as T
            is Boolean -> getBoolean(key, default) as T
            is Float -> getFloat(key, default) as T
            is Set<*> -> getStringSet(key, default as Set<String>) as T
            is MutableSet<*> -> getStringSet(key, default as MutableSet<String>) as T
            else -> throw IllegalArgumentException("generic type not handled")
        }
    }
// usage
    prefs.observeKey("key", "").collect { string ->  }