Androidアプリ開発でRoomを学ぶ者

dependencies {
    val room_version = "2.8.4"
    implementation("androidx.room:room-runtime:$room_version") //Room基本ライブラリ
    implementation("androidx.room:room-ktx:$room_version") //Room拡張機能
    ksp("androidx.room:room-compiler:$room_version") //Roomコード生成コンパイラ

    //▼以下はログを追加テストするボタン用
    val lifecycle_version = "2.10.0"
    implementation("androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version")
    implementation("androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_version")

    val coroutines_version = "1.8.1"
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:$coroutines_version")
}

plugins{
    id("com.google.devtools.ksp") version "2.0.21-1.0.26" //kspプラグイン読み込み
}

package com.example.roomtest2.data.db

import androidx.room.Entity
import androidx.room.PrimaryKey

@Entity(tableName = "logs")
data class Log(
    @PrimaryKey(autoGenerate = true)
    val id: Long = 0, //必須
    val timestamp: Long = System.currentTimeMillis(), //必須
    val title: String, //必須
    val action: String, //必須
    val detail: String? = null //?が付いているため任意扱い
)

package com.example.roomtest2.data.db

import androidx.room.Dao
import androidx.room.Insert
import androidx.room.Query

@Dao
interface LogDao {
    @Insert
    suspend fun insert(log: Log)

    @Query("SELECT * FROM logs ORDER BY timestamp DESC")
    suspend fun getLatest(): List<Log>

    @Query("DELETE FROM logs  WHERE timestamp < :limit")
    suspend fun deleteLogLimit(limit:Long)
}

package com.example.roomtest2.data.db

import android.content.Context
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase

@Database(
    entities = [
        Log::class,//複数ある場合は必要なだけ列挙
    ],
    version = 1, //スキーマ構造の変更が必要な場合はカウントアップし、マイグレーションを促す
    exportSchema = true //バージョンごとにスキーマJSONを保存する、保存先はgradleで指定する
)

abstract class DataBase : RoomDatabase(){
    abstract fun LogDao(): LogDao
    companion object {
        @Volatile //スレッド間で必ず最新の変数を参照
        private var INSTANCE: DataBase? = null

        fun getInstance(context: Context): DataBase {
            //INSTANCEが空であれば初期化する
            return INSTANCE ?: synchronized(this) {

                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    DataBase::class.java,
                    "log_database.db" //.dbは必須ではない
                ).build()
                INSTANCE = instance
                instance
            }
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/addButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ログを追加する"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.109" />
</androidx.constraintlayout.widget.ConstraintLayout>

package com.example.roomtest2.data

import android.app.Application
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.viewModelScope
import com.example.roomtest2.data.db.DataBase
import com.example.roomtest2.data.db.Log
import com.example.roomtest2.data.db.LogDao

import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch

class AppViewModel(app: Application) : AndroidViewModel(app) {

    private lateinit var dao: LogDao
    //コンストラクタ
    init{
        val db = DataBase.getInstance(app)
        dao = db.LogDao()
    }

    fun onLogButtonClicked(){
        viewModelScope.launch { (Dispatchers.IO)
            //INSERT用のデータを作成
            val log = Log(
                title = "test" + System.currentTimeMillis().toString(),
                action = "追加した",
                detail = "詳しい処理を記載"

            )
            //INSERT実行
            dao.insert(log)
        }
    }
}

package com.example.roomtest2

import android.os.Bundle
import android.widget.Toast
import androidx.activity.enableEdgeToEdge
import androidx.activity.viewModels
import androidx.appcompat.app.AppCompatActivity
import com.example.roomtest2.data.AppViewModel
import com.example.roomtest2.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding
    private val appViewModel: AppViewModel by viewModels()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        //setContentView(R.layout.activity_main)
        //ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets ->
        //    val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
        //    v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
        //    insets
        //}
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        binding.addButton.setOnClickListener {
            appViewModel.onLogButtonClicked()
            Toast.makeText(this,"押した",Toast.LENGTH_SHORT).show()
        }
    }
}