Faced such a problem: I have a RecyclerView, the data for which I get from the ViewModel using StateFlow:

viewModel.items.collect {
    setRecyclerView(items)
}

Then, let's say, somewhere inside the Fragment, I change the data for items and there are more of them. In order for my RecyclerView to see my changes, I have to call the setRecyclerView(items) function again, which, it seems to me, can lead to the most unexpected consequences (for example, items will be duplicated). The question is: is it possible to somehow change the data and update the RecyclerView (including the onBindViewHolder function in it) without yet another creation of an Adapter?

CodePudding user response：

Let's start talking about the adapter implementation. Reading your question, I believe you used RecyclerView.Adapter to implement your adapter. But there is another option that is simpler and more performant than this. It's the ListAdapter:

The most interesting thing about ListAdapter is the DiffUtil, that have a performative way to check if any item on your list was updated, deleted, or included. Here's a sample of the implementation:

abstract class MyAdapter: ListAdapter<ItemModel, MyAdapter.MyViewHolder>(DIFF_CALLBACK) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val binding = ItemSimplePosterBinding.inflate(
            LayoutInflater.from(parent.context),
            parent,
            false
        )
        return MyViewHolder(binding)
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        holder.bind(getItem(position))
    }

    class MyViewHolder(
        private val binding: ItemSimplePosterBinding
    ): RecyclerView.ViewHolder(binding.root) {

        fun bind(item: ItemModel) {
            // Here you can get the item values to put these values on your view
        }

    }

    companion object {
        private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<ItemModel>() {
            override fun areItemsTheSame(oldItem: ItemModel, newItem: ItemModel): Boolean {
                // need a unique identifier to have sure they are the same item. could be a comparison of ids. In this case, that is just a list of strings just compares like this below
                return oldItem.id == newItem.id
            }

            override fun areContentsTheSame(oldItem: ItemModel, newItem: ItemModel): Boolean {
                // compare the objects
                return oldItem == newItem
            }

        }
    }
}

So, when your list is updated, you just have to call the submitList from the adapter, like this:

viewModel.items.collectLatest { items ->
     // You will send the items to your adapter here
     adapter.submitList(items)
}

Then, your RecyclerView just has to be configured on onViewCreated for example, and your list can be defined and updated in another place, observing the items change from ViewModel.