Android/kotlin/db/room
提供: 初心者エンジニアの簡易メモ
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" }
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)
参考
- https://re-engines.com/2019/10/24/%E3%80%90kotlin%E3%80%91room%E3%81%A7db%E7%AE%A1%E7%90%86%E3%82%92%E3%81%99%E3%82%8B/
- https://developer.android.com/training/data-storage/room/accessing-data
- https://developer.android.com/training/data-storage/room
- https://qiita.com/niusounds/items/fff5e83489e69d7924fd
- https://android.jlelse.eu/android-room-using-kotlin-f6cc0a05bf23
- https://gabrieltanner.org/blog/android-room