如何通过带有Kotlin的房间ORM在Android应用程序中使用现有数据库

implementation "androidx.room:room-runtime:2.4.0"
kapt "androidx.room:room-compiler:2.4.0"

@Entity(tableName = "users")
data class User(
    @PrimaryKey val id: Int,
    @ColumnInfo(name = "name") val name: String,
    @ColumnInfo(name = "age") val age: Int
)

@Dao
interface UserDao {
    @Query("SELECT * FROM users")
    fun getAllUsers(): List<User>

    @Insert
    fun insertUser(user: User)

    @Update
    fun updateUser(user: User)

    @Delete
    fun deleteUser(user: User)
}

@Database(entities = [User::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun userDao(): UserDao
}

val db = Room.databaseBuilder(applicationContext, AppDatabase::class.java, "my-database").build()
val userDao = db.userDao()

val users = userDao.getAllUsers() // 获取所有用户
val newUser = User(1, "John", 25)
userDao.insertUser(newUser) // 插入新用户
newUser.age = 26
userDao.updateUser(newUser) // 更新用户信息
userDao.deleteUser(newUser) // 删除用户