How to refresh list item after sorting immediately

Issue

I have a music list obtained from:

MusicDatabase.kt

override fun getContentProviderValue(): MutableList<Songs> {

    val songList =  mutableListOf<Songs>()
    val collection = sdk29AndUp {
        MediaStore.Audio.Media.getContentUri(MediaStore.VOLUME_EXTERNAL)
    } ?:  MediaStore.Audio.Media.EXTERNAL_CONTENT_URI

    //Get songs from provider
    context.contentResolver.query(
        collection,
        projection,
        selection,
        null,
        PreferenceHelper.storeAllSongsSortOrder //Sort order.
    ).use { cursor -> 
    ............
 }
}

Using SharedPreference, I am storing and obtaining sort order like this:

PreferenceHelper.kt

//store allSongs sort order
var storeAllSongsSortOrder: String?
    get() = preferences.getString(allSongSortOrder.first, allSongSortOrder.second)
    set(value) = preferences.edit {
        if (value != null) {
          it.putString(allSongSortOrder.first, value)
    }
}

I obtain the songList like this:

SongsFragment.kt

 mainViewModel.mediaItems.observe(viewLifecycleOwner){ result->
 when(result.status) {
 Status.SUCCESS -> {
 result.data?.let { songs ->        
 allSongsAdapter.songs = songs
 ........
 }

In my songs fragment, when user clicks "Sort", a dropdown will appear with 2 options:

1. Sort by name
2. Sort by date

When user clicks sort by name, I do this:

SongsFragment.kt

PreferenceHelper.storeAllSongsSortOrder = Constants.SORT_TITLE
binding.rcvAllSongs.invalidate()
allSongsAdapter.notifyDataSetChanged()

When user clicks sort by date, I do this:

 PreferenceHelper.storeAllSongsSortOrder = Constants.SORT_LAST_ADDED
 binding.rcvAllSongs.invalidate()
 allSongsAdapter.notifyDataSetChanged()

PROBLEM: The list is not updating real time as I select, I have to close the app and open before my list gets the selected sort order.

I want - when I click e.g "Sort by date" - The list should update immediately and display songs based on date added.

Solution

You can propably do something like this:

class YourFragment : Fragment {
 
  private val allSongsAdapter = SongsAdapter()

  override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
  ): View {
    //init your views, bindins, view model and your recycler view adapter
    //...
    binding.recyclerView.adapter = allSongsAdapter
  }
  
  //...
  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    mainViewModel.songList.observe(viewLifecycleOwner, { result ->
      when (result.status) {
        Status.SUCCESS -> {
          allSongsAdapter.updateList(result.data)
        }
      }
    })
    
    //or whatever you have on your UI to change your filter
    binding.sortFilter.setOnClickListener { filter ->
      mainViewModel.updateSortFilter(filter)
    }
    
    //....
    viewModel.initList()
  }
}

class YourViewModel() : ViewModel() {

  private var _unsortedSongList: List<String> = emptyList()
  
  private val _songList = MutableLiveData<Songs>()
  val songList: LiveData<Songs> = _songList

  private lateinit var musicDatabase: MusicDatabase

  init {
    musicDatabase = //get the dependency or inject it from constructor
    _unsortedSongList = musicDatabase.getContentProviderValue()
  }

  fun initList() {
    _songList.value = sortSongs(PreferencesHelper.storeAllSongsSortOrder)
  }

  fun updateSortFilter(sortFilter: String) {
    PreferencesHelper.storeAllSongsSortOrder = sortFilter
    _songList.value = sortSongs(sortFilter)
  }

  private fun sortSongs(sortFilter: String): List<Songs> {
    var sortedList: List<Songs> = emptyList()
    switch (sortFilter) {
      Constants.SORT_LAST_ADDED -> {
        sortedList = _unsortedSongList.sortedBy { it.createdMillis }
      }
      Constants.SORT_LAST_ADDED -> {
        sortedList = _unsortedSongList.sortedBy { it.name }
      }
    }
    return sortedList
  }


}

class SongsAdapter : RecyclerView.Adapter<SongItemAdapter.ViewHolder> {
  private val songsList = mutableListOf<Songs>()

  fun updateList(list: List<Songs>) {
    songsList.clear()
    songsList.addAll(list)
    notifyDataSetChanged()
  }

  //.... the rest of your adapter and viewholder
}

Answered By - MatPag