How can I update LiveData<List> from another class?

Question

So I have a list in my ViewModel that whenever suffers changes, they get reflected on the UI through DataBinding.

private val _entries = MutableLiveData<List<BarEntry>>()
val entries: LiveData<List<BarEntry>>
    get() = _entries

ISortingAlgorithm is an interface that represents a sorting algorithm.

interface ISortingAlgorithm
{
    fun sort(listToSort: List<BarEntry>)
}

Example (not the final implementation) of a concrete class implementing ISortingAlgorithm:

class BubbleSort : ISortingAlgorithm
{
    override fun sort(listToSort: List<BarEntry>)
    {
        Log.d(this::class.java.canonicalName, "Applying sort")

        for(currentPass in 0 until (listToSort.size - 1))
        {
            for(currentPosition in 0 until (listToSort.size - currentPass - 1))
            {
                if(listToSort[currentPosition].y > listToSort[currentPosition + 1].y)
                {
                    val temp = listToSort[currentPosition].y
                    listToSort[currentPosition].y = listToSort[currentPosition+1].y
                    listToSort[currentPosition+1].y = temp
                }
                Thread.sleep(10)
            }
        }
    }
}

In my ViewModel I have a lateinit var sortingAlgorithm: ISortingAlgorithm. When I call sortingAlgorithm.sort(_entries.value) I want the UI to reflect all the modifications done to the list at each step, not just the final result. How can this be done?

My solution right now is for sort() to return all the intermediate states of the list and then apply the changes to the original LiveData list in the viewmodel but this seems like a workaround not a solution.

Answer 1

Build a LiveData using Kotlin extensions in your ViewModel.

lateinit var sorter: ISortingAlgorithm

fun getLiveData(listToSort: List<BarEntry>)
        : LiveData<List<BarEntry>> = androidx.lifecycle.liveData {
    emit(listToSort)
    while (sorter.sort(listToSort)) 
        emit(listToSort)
}

sort() can be modified to return a boolean that indicates whether a sort step just occurred. Sorting terminates when a step cannot occur.