getValue method
Gets the value from SharedPreferences.
If the value doesn't exist and defaultValue is provided, stores the default value and returns it.
Implementation
Future<T?> getValue(SharedPreferencesAsync prefs) async {
final value = await adapter.getter(prefs, key);
if (value == null && defaultValue != null) {
await setValue(prefs, defaultValue as T);
return defaultValue;
}
return value;
}