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Android/kotlin/db/room

提供: 初心者エンジニアの簡易メモ
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Roomとは

SQLiteのマッパーライブラリ

公式：https://developer.android.com/training/data-storage/room

Androidでも公式が、強くおすすめすると書いてる。

準備

app/build.gradle 

apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-kapt'
dependencies {
    implementation 'android.arch.persistence.room:runtime:1.0.0'
    annotationProcessor  'android.arch.persistence.room:compiler:1.0.0'
    kapt 'android.arch.persistence.room:compiler:1.0.0'
    
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.3"
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.3"
}

https://codelabs.developers.google.com/codelabs/android-room-with-a-view-kotlin/#2

サンプル

schema1.usersのテーブルを置く時のサンプル

Schema1Database.kt 

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

@Database(entities = arrayOf(UserEntity::class), version = 1)
abstract class Schema1Database: RoomDatabase() {
    abstract fun userDao(): UserDao
    companion object {
        @Volatile
        private var INSTANCE: Schema1Database? = null
        fun getDatabase(context: Context): Schema1Database {
            val tempInstance = INSTANCE
            if (tempInstance != null) {
                return tempInstance
            }
            synchronized(this) {
                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    Schema1Database::class.java,
                    "schema1.db"
                ).build()
                INSTANCE = instance
                return instance
            }
        }
    }
}

UserEntity.kt 

import androidx.room.Entity
import androidx.room.PrimaryKey
@Entity(tableName = "users")
data class UserEntity constructor(
    @PrimaryKey(autoGenerate = true)
    val id: Int,
    val name: String
)

UserDao.kt 

import androidx.room.Dao
import androidx.room.Insert
import androidx.room.Query
import androidx.room.Update
import androidx.room.Delete
import androidx.room.OnConflictStrategy

@Dao
interface UserDao {
    @Query("SELECT * from users")
    fun getAll(): List<UserEntity>

    @Query("SELECT * FROM users WHERE id IN (:userIds)")
    fun loadAllByIds(vararg userIds: Int): List<UserEntity>

    @Query("SELECT * FROM users WHERE name LIKE :name")
    fun findByLikeName(name: String): UserEntity

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun insert(user: UserEntity)

    @Insert
    fun insertAll(vararg users: UserEntity)

    @Update
    fun update(user: UserEntity)

    @Update
    fun updateUsers(vararg users: UserEntity)

    @Delete
    fun delete(user: UserEntity)

    @Delete
    fun deleteUsers(users: List<UserEntity>)

    @Query("DELETE FROM users")
    fun deleteAll()
}

@Insert(onConflict = OnConflictStrategy.REPLACE) は同一idの場合に置き換えされる

db呼び出し

MainActivity.kt 

class MainActivity : AppCompatActivity() {
    val scope = CoroutineScope(Dispatchers.Default)
    lateinit var db: Schema1Database
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        db = Schema1Database.getDatabase(applicationContext)
        scope.launch {
            dbTask()
        }
    }
    private suspend fun dbTask() {
        try {
            dbExec()
        } catch (e: Exception) {
            Log.e(localClassName, "onCancelled", e)
        }
    }
    private fun dbExec() {
        val dao = db.userDao()
        dao.insert(UserEntity(0, "rei"))
        dao.insert(UserEntity(1, "taro"))
        dao.insert(UserEntity(2, "jiro"))
        var users: List<UserEntity> = dao.getAll()
        for (user: UserEntity in users) {
            Log.i("db", "id=" + user.id.toString() + " name=" + user.name);
        }
        for (user: UserEntity in users) {
            if (user.id == 2) {
                Log.i("db", "upd id=" + user.id.toString() +" name=" + user.name);
                dao.update(UserEntity(user.id, "siro"))
            } else {
                Log.i("db", "del id=" + user.id.toString() +" name=" + user.name);
                dao.delete(UserEntity(user.id, user.name));
            }
        }
        users = dao.getAll()
        for (user: UserEntity in users) {
            Log.i("db", "del id=" + user.id.toString() +" name=" + user.name);
            dao.delete(UserEntity(user.id, user.name));
        }
    }
}

出力 

2020-01-14 16:16:51.109 24379-24416/? I/db: id=1 name=taro
2020-01-14 16:16:51.109 24379-24416/? I/db: id=2 name=jiro
2020-01-14 16:16:51.109 24379-24416/? I/db: id=21 name=rei
2020-01-14 16:16:51.109 24379-24416/? I/db: del id=1 name=taro
2020-01-14 16:16:51.110 24379-24416/? I/db: upd id=2 name=jiro
2020-01-14 16:16:51.111 24379-24416/? I/db: del id=21 name=rei
2020-01-14 16:16:51.114 24379-24416/? I/db: del id=2 name=siro

idが0のinsertはauto_incrementのmax値が入る？

更新処理

上記例では新規UserEntityを作って入れたが、 

dao.update(UserEntity(user.id, "siro"))

変更するプロパティをvalからvarに変えて、更新していれることもできる

UserEntity.kt 

data class UserEntity constructor(
    @PrimaryKey(autoGenerate = true)
    val id: Int,
    var name: String
)

user.name = "siro"
dao.update(user)

以下のような修飾子を用意

@Insert(onConflict = OnConflictStrategy.REPLACE)
@Insert(onConflict = OnConflictStrategy.ROLLBACK)
@Insert(onConflict = OnConflictStrategy.ABORT)

参考：https://tech.recruit-mp.co.jp/mobile/post-12311/

insertしたときにidを返す場合

戻り値の型にLongを設定すれば良い。 

@Dao
interface UserDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun insert(user: UserEntity): Long
}

呼び出しサンプル 

var id = dao.insert(UserEntity(2, "jiro"))
Log.i("db", "id=" + id.toString()) // 2

updateした行数を返す場合

updateの戻り値の型にIntを設定する 

@Dao
interface UserDao {
    @Update
    fun update(user: UserEntity): Int
}

呼び出しサンプル 

var cnt = dao.update(user)
Log.i("db", "cnt=" + cnt.toString()) // 1

sql失敗時の処理

try {
    var ret = dao.insert(UserEntity(9223372036854775807, "jiro"))
    Log.i("test", "ret insert id=" + ret.toString())
} catch (e: SQLiteException) {
    Log.i("test", "error message=" + e.message)
}

sqliteのintの上限値(9223372036854775807)で一度データを入れ、次にidを0指定してauto_incrementさせると以下エラーがe.messageで発生した。 

cannot rollback - no transaction is active (code 1 SQLITE_ERROR)

insert失敗時の処理

isnertをIGNOREにしてみて、同じidを入れてみた所、失敗として、-1が返ってきた。

UserDao.kt 

@Dao
interface UserDao {
    @Insert(onConflict = OnConflictStrategy.IGNORE)
    fun insert(user: UserEntity): Int
}

MainActivity.kt 

 var ret = dao.insert(UserEntity(1234, "jiro"))
 Log.i("test", "ret insert id=" + ret.toString()) // 1234
 var ret2 = dao.insert(UserEntity(1234, "jiro"))
 Log.i("test", "ret2 insert id=" + ret2.toString()) // -1

参考：https://tutorialmore.com/questions-756651.htm

likeの%をアノテーション定義に書く場合

@Query("SELECT * FROM users WHERE name LIKE '%' || :date || '%'")
fun findByLikeDate(date: String): UserEntity

参考：https://stackoverflow.com/questions/44184769/android-room-select-query-with-like

db定義変更時

以下エラーが発生する場合 

Caused by: java.lang.IllegalStateException: Room cannot verify the data integrity. Looks like you've changed schema but forgot to update the version number. You can simply fix this by increasing the version number.

未リリースのときはアプリのデータを削除するだけで直る

参考：https://translate.google.com/translate?sl=en&tl=ja&u=https://stackoverflow.com/questions/44197309/room-cannot-verify-the-data-integrity

参考

「https://wiki.nonip.net/index.php?title=Android/kotlin/db/room&oldid=10451」から取得