从概念上讲，我如何使用LiveData和房间执行一个简单的读取/更新周期？

// 定义实体类
@Entity(tableName = "users")
public class User {
    @PrimaryKey
    public int id;
    public String name;
    public int age;
}

// 创建数据访问对象（DAO）
@Dao
public interface UserDao {
    @Query("SELECT * FROM users")
    LiveData<List<User>> getUsers();

    @Update
    void updateUser(User user);
}

// 创建数据库
@Database(entities = {User.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
    public abstract UserDao userDao();
}

// 初始化LiveData对象
public class MyViewModel extends ViewModel {
    private LiveData<List<User>> users;
    private UserDao userDao;

    public MyViewModel() {
        userDao = Room.databaseBuilder(context, AppDatabase.class, "database-name").build().userDao();
        users = userDao.getUsers();
    }

    public LiveData<List<User>> getUsers() {
        return users;
    }

    public void updateUser(User user) {
        userDao.updateUser(user);
    }
}

// 观察数据
public class MyActivity extends AppCompatActivity {
    private MyViewModel viewModel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        viewModel = ViewModelProviders.of(this).get(MyViewModel.class);
        viewModel.getUsers().observe(this, new Observer<List<User>>() {
            @Override
            public void onChanged(List<User> users) {
                // 更新UI
            }
        });
    }
}

// 更新数据
public class MyActivity extends AppCompatActivity {
    private MyViewModel viewModel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        viewModel = ViewModelProviders.of(this).get(MyViewModel.class);

        // 更新数据
        User user = new User();
        user.id = 1;
        user.name = "John";
        user.age = 25;
        viewModel.updateUser(user);
    }
}