room.kt

package com.penguinshunya.myapplication

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.Button
import androidx.room.*
import kotlin.random.Random

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val btn = findViewById<Button>(R.id.mybutton)
        btn.setOnClickListener {
            Thread(Runnable {
                val db = Room.databaseBuilder(
                    applicationContext,
                    AppDatabase::class.java, "database-name",
                ).build()
                val dao = db.userDao()

                val user = User(Random.nextInt(0, 100000), "takaya", "fujimoto")
                dao.insertAll(user)

                for (user in dao.getAll()) {
                    Log.e("Error", user.toString())
                }
            }).start()
        }
    }

    override fun onResume() {
        super.onResume()
    }
}

@Entity
data class User(
    @PrimaryKey val uid: Int,
    @ColumnInfo(name = "first_name") val firstName: String?,
    @ColumnInfo(name = "last_name") val lastName: String?,
)

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

    @Query("SELECT * FROM user WHERE uid IN (:userIds)")
    fun loadAllByIDs(userIds: IntArray): List<User>

    @Query("SELECT * FROM user WHERE first_name LIKE :first AND last_name LIKE :last LIMIT 1")
    fun findByName(first: String, last: String): User

    @Insert
    fun insertAll(vararg users: User)

    @Delete
    fun delete(user: User)
}

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