Why not auto update list when used LiveData in Android-CodePudding

In my application I want use Koin , Room and LiveData.
I write below codes, but after add new item into room not auto update recyclerview list!
Should close app and open again for show updated list !

Dao codes :

@Query("SELECT * FROM $NOTE_TABLE")
fun getAllNote(): MutableList<NoteModel>

Repository codes :

class RoomRepository(private val dao: NoteDao) {

    suspend fun saveNote(note: NoteModel) = dao.saveNote(note)
    fun getAllNotes() = dao.getAllNote()

}

ViewModel codes:

class RoomViewModel(private val repository: RoomRepository) : ViewModel() {

    val notesList = MutableLiveData<MutableList<NoteModel>>()

    fun saveNote(note:NoteModel) = viewModelScope.launch {
        repository.saveNote(note)
    }

    fun loadAllNotes() = viewModelScope.launch {
        val list = repository.getAllNotes()
        if (list.isNotEmpty()) {
            notesList.postValue(list)
        }
    }
}

Activity codes :

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityKoinRoomBinding.inflate(layoutInflater)
        setContentView(binding.root)
        //InitViews
        binding.apply {
            //Save
            btnSave.setOnClickListener {
                val title = titleEdt.text.toString()
                note.id = 0
                note.title = title
                viewModel.saveNote(note)
            }
            //Load notes
            viewModel.loadAllNotes()
            viewModel.notesList.observe(this@KoinRoomActivity) {
                noteAdapter.differ.submitList(it)

                notesList.apply {
                    layoutManager = LinearLayoutManager(this@KoinRoomActivity)
                    adapter = noteAdapter
                }
            }
        }

How can I fix this issue?

CodePudding user response：

In order to update data immediately, you need to return LiveData<T> from the database itself. In your case, do something like that:

@Query("SELECT * FROM $NOTE_TABLE")
fun getAllNote(): LiveData<List<NoteModel>>

I also changed MutableList to List, because there is no need for mutability here.

You ViewModel can then be like this:

class RoomViewModel(private val repository: RoomRepository) : ViewModel() {

    val notesList = repository.getAllNotes()

    ...
}

and you can also remove function loadAllNotes() from it.

CodePudding user response：

Try changing the return type in the DAO and observe it from the activity. Then, add it to the recyclerview adaper

Change this

fun getAllNote(): MutableList<NoteModel>

fun getAllNote(): LiveData<List<NoteModel>>