update method
Updates the value asynchronously.
Implementation
Future<void> update(T value) async {
if (value is String) {
await prefs.setString(prefKey, value);
} else if (value is bool) {
await prefs.setBool(prefKey, value);
} else if (value is int) {
await prefs.setInt(prefKey, value);
} else if (value is double) {
await prefs.setDouble(prefKey, value);
} else if (value is List<String>) {
await prefs.setStringList(prefKey, value);
}
super.state = value;
}