[移动开发]Room的简单使用

引入依赖

id 'kotlin-kapt'

implementation "androidx.room:room-runtime:2.1.0"
kapt "androidx.room:room-compiler:2.1.0"

Entity实体类

@Entity
data class User(
    var firstName: String,
    var lastName: String,
    var age: Int,
) {
    @PrimaryKey(autoGenerate = true)
    var id: Long = 0
}

Dao逻辑封装

@Dao
interface UserDao {
    @Insert
    fun insertUser(user: User): Long

    @Update
    fun updateUser(user: User)

    @Query("select * from User")
    fun selectAllUser(): List<User>

    @Delete
    fun deleteUser(user: User)

    @Query("delete from User where lastName = :lastName")
    fun deleteUserByLastName(lastName: String)
}

Database提供实例

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

    companion object {
        private var instance: AppDatabase? = null

        @Synchronized
        fun getDatabase(context: Context): AppDatabase {//单例
            if (instance == null) {
                instance = Room.databaseBuilder(
                    context.applicationContext,
                    AppDatabase::class.java,
                    "app_database"
                ).build()
            }
            return instance!!
        }
    }
}

简单使用

val userDao = AppDatabase.getDatabase(this).userDao()
val user1 = User("小", "名", 12)
addButton.setOnClickListener {
    thread {
        user1.id = userDao.insertUser(user1)
    }
}