As shown in the image, I would like the unit of the Detail item to be changed at once according to the toggle button.
Detail list items were set as companion objects because it was determined that it was not necessary to have a unit property individually.
However, it seems that DiffUtil determines that there is no change between the new list and the old list, perhaps because the unit property is set as a companion object.
So there is no update of the view either.
How can I make DiffUtil responsive while changing the companion object?
Detail
@Entity
data class Detail(
@PrimaryKey(autoGenerate = true)
var id: Int,
val set: Int,
var weight: String = "",
var reps: String = "") {
companion object {
var title: String = ""
var unit: String = "kg"
val memo = ""
}
}
ViewModel
class DetailViewModel(application: Application) : ViewModel() {
private val repository: DetailRepository
private val _items: MutableLiveData<List<Detail>> = MutableLiveData()
val items = _items
private val list: List<Detail>
get() = _items.value ?: emptyList()
init {
val detailDao = DetailDatabase.getDatabase(application)!!.detailDao()
repository = DetailRepository(detailDao)
}
fun changeUnit(unit: String) {
Detail.unit = unit
if(list == null)
return
_items.postValue(list) // To notify the observer.
}
fun addDetail() {
viewModelScope.launch(Dispatchers.IO){
val item = Detail(0, set = list.size+1)
repository.add(item)
// If use plus(), a new List is returned.
// Therefore, the change is notified to the Observer by postValue of the new list added.
_items.postValue(list.plus(item))
}
}
fun deleteDetail() {
// Delete the last set and return a new list to postValue to notify the Observer of the change.
_items.postValue(list.dropLast(1))
}
}
DiffUtil
class DetailDiffCallback : DiffUtil.ItemCallback<Detail>() {
override fun areItemsTheSame(
oldItem: Detail,
newItem: Detail
): Boolean {
return (oldItem.id == newItem.id)
}
override fun areContentsTheSame(
oldItem: Detail,
newItem: Detail
): Boolean {
return oldItem == newItem
}
}
Fragment
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
vm.items.observe(viewLifecycleOwner) { newList ->
adapter.submitList(newList)
}
}
