RoomList

How to use Room Library to persistence data into Android Application

There are 3 main classes that I used to create the example.

ToDoViewModel It helps to show the data from repository class. Live Data uses Observable/Observer to notify data changes.

Create new executors to insert/delete/update objects into database using Room.

ToDoRepository Get and insert data. Repository uses LiveData to notify by using changes to observer objects.

Room Database

Persistence Implementation by using Room Android Library

LiveData

    var dataLive:LiveData<List<ToDo>> = MutableLiveData<List<ToDo>>()
    

ViewModel

        val viewModel = ViewModelProviders.of(this).get(ToDoViewModel::class.java)
        viewModel.dataLive.observe(this,Observer{
            list ->  adapter.addItems(list as ArrayList<ToDo>)
        })

Database

@Dao
interface ToDoDao {

    @Query("SELECT * FROM todo ORDER BY date DESC")
    fun getAll():LiveData<List<ToDo>>

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun insert(vararg todo:ToDo)

    @Delete
    fun delete(todo:ToDo)

    @Update
    fun update(vararg todo: ToDo)
}

@Database(entities = arrayOf(ToDo::class),version = 1)
abstract class ToDoDatabase:RoomDatabase() {
    abstract fun toDoDao():ToDoDao
}