[Android, Kotlin] 안드로이드 어플 출시까지 한 걸음 부터(3), 데이터 베이스 구조 만들기(Room, E-R Diagram)

Room

Room 지속성 라이브러리  |  Android 개발자  |  Android Developers

안드로이드 내부 데이터베이스 Room을 사용하여 "나만의 타이머"에서 사용될 데이터를 관리하도록 하였습니다.

Room DB를 사용한 과정

 

Table의 역활을 할 Model

//외래키 설정
@Entity(foreignKeys = [ForeignKey(
    entity = Title::class,
    parentColumns = ["title"],
    childColumns = ["todo_title"],
    onDelete = CASCADE,	
    onUpdate = CASCADE
)]
)
//Table 데이터 정보
data class Todo(
    val todo_title : String?,
    var todo : String?,
    val success : Boolean? = false,
    @PrimaryKey(autoGenerate = true)
    var id : Int? = 0
)

위 모델은 목표에 대한 Todo(할 일)을 저장하는 Table입니다.

 

데이터베이스에 SQL 명령어(Insert, Select...)을 포함된 Dao

@Dao
interface DAO {
    //Room DB Insert SQL
    @Insert
    suspend fun titleAdd(title: Title)

    @Query("INSERT INTO Todo(todo_title, todo, success) VALUES(:title, :todo, :success)")
    suspend fun todoAdd(title : String,todo : String, success:Boolean)

    @Query("INSERT INTO CalendarTime(calendar_title,time_date) VALUES(:title,:date)")
    suspend fun calendarTimeAdd(title : String, date : String)
    .....
    //Room DB Update SQL
    @Query("UPDATE Todo SET success = :success WHERE todo = :todo AND todo_title = :title")
    suspend fun todoSuccessUpdate(title : String, todo : String, success: Boolean)

    @Query("UPDATE CalendarTodo SET success = :success Where todo = :todo AND todo_date = :date AND calendar_title = :title")
    suspend fun calendarTodoSuccessUpdate(title: String, todo: String, success: Boolean, date: String)

    @Query("UPDATE CalendarTime SET time = time + :time Where calendar_title = :title AND time_date = :date")
    suspend fun timeUpdate(time : Long, title : String, date: String)
    .....
    
    //Room DB SELECT SQL
    @Query("SELECT COUNT(title) FROM Title")
    suspend fun getTitleCount() : Int

    @Query("SELECT * FROM Title LEFT OUTER JOIN Todo ON Title.title == Todo.todo_title")
    suspend fun getInfo() : List<TitleAndTodo>?

    @Query("SELECT * FROM Title")
    suspend fun getTitle() : List<Title>
    ....
    
    //Room DB DELETE SQL
    @Query("DELETE FROM Todo WHERE todo_title = :title AND todo = :todo")
    suspend fun deleteTodo(title : String, todo : String)

    @Query("DELETE FROM CalendarTodo WHERE calendar_title = :title AND todo = :todo AND todo_date = :date")
    suspend fun deleteCalendarTodo(title : String, todo : String, date : String)

    @Query("DELETE FROM Title WHERE title = :title")
    suspend fun deleteTitle(title : String)

저는 Room DB를 Build를 진행하는 것을 Application에서 한 번 진행하여 Build가 반복되는 것을 방지하도록 하였습니다.

class GlobalApplication : Application() {
    companion object{
        ....
        lateinit var databaseInstance : DB
            private set
    }

    override fun onCreate() {
        super.onCreate()
        ...
        databaseInstance = Room.databaseBuilder(
            appInstance.applicationContext,
            DB::class.java,
            "DB"
        )
            .fallbackToDestructiveMigration()
            .allowMainThreadQueries()
            .build()
    }
}

Dao에 저장된 내용들을 Room에 실행하여 데이터를 가져오거나 저장하는 것을 수행하는 Repository

class Repo{
    private val dbInstance = GlobalApplication.databaseInstance.dao()

    //Insert Call
    suspend fun titleInsert(title: Title){
        dbInstance.titleAdd(title)
    }
    suspend fun todoInsert(title : String, todo : String, success : Boolean ){
        dbInstance.todoAdd(title,todo,success)
    }
    ...
    
    //Update Call
    suspend fun todoSuccessUpdate(title : String, todo : String, success: Boolean){
        dbInstance.todoSuccessUpdate(title, todo, success)
    }
    suspend fun calendarTodoSuccessUpdate(title : String, todo: String, success: Boolean, date: String){
        dbInstance.calendarTodoSuccessUpdate(title, todo, success, date)
    }
    ...
    
    //Delete Call
    suspend fun deleteTodo(todo :String, title : String){
        dbInstance.deleteTodo(title, todo)
    }
    suspend fun deleteCalendarTodo(todo:String, title : String, date: String){
        dbInstance.deleteCalendarTodo(title, todo, date)
    }
    ...
    
    //Select Call
    suspend fun getInfo() = dbInstance.getInfo()
    suspend fun getTitleCount() = dbInstance.getTitleCount()

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E-R Diagram

개체-관계 모델 - 위키백과, 우리 모두의 백과사전