putObject method
存储对象 class User {
Implementation
// final String name;
// final int age;
//
// User({required this.name, required this.age});
//
// Map<String, dynamic> toJson() => {'name': name, 'age': age};
//
// factory User.fromJson(Map<String, dynamic> json) {
// return User(name: json['name'], age: json['age']);
// }
// }
// await spUtil.putObject("user", user.toJson());
// User? loadedUser = spUtil.getObject("user", User.fromJson);
Future<bool> putObject(String key, Object value) => _put(key, value);