RoomActivity.kt

package com.leonidivankin.draftsandroid.articles.db

import android.os.Bundle
import android.util.Log
import androidx.appcompat.app.AppCompatActivity
import androidx.room.*
import androidx.room.OnConflictStrategy.REPLACE

class RoomActivity : AppCompatActivity() {

    private val colorDao by lazy {
        Room
            .databaseBuilder(applicationContext, AppDatabase::class.java, "colors_room")
            .build()
            .colorDao()
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Thread {
            val list = listOf(Color(1, "green"), Color(2, "red"), Color(3, "blue"))
            colorDao.insert(list)
            Log.d("DbExample", "${colorDao.get()}")
        }.start()
    }
}

@Database(entities = [Color::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
    abstract fun colorDao(): ColorDao
}

@Entity(tableName = "colors")
data class Color(@PrimaryKey val id: Int, val color: String)

@Dao
interface ColorDao {
    @Query("SELECT * FROM colors") fun get(): List<Color>
    @Insert(onConflict = REPLACE) fun insert(color: List<Color>)
}