RecyclerView(DiffUtil+ListAdapter) strange behavior after delete item

Question

RecyclerView after delete any item lift bottom item up and redraw it at the same time. It looks strange. How can i solve this problem? (how it looks https://youtu.be/hKmNWwfxfzM !)

val swipeHandler = object : SwipeToDeleteCallback(requireContext()) {
            override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
                viewModel.deleteNote(viewModel.noteListLiveData.value!![viewHolder.adapterPosition])
            }
        }
        val itemTouchHelper = ItemTouchHelper(swipeHandler)
        itemTouchHelper.attachToRecyclerView(binding.noteRecyclerView)

Use LiveData to update RV

viewModel.noteListLiveData.observe(
            viewLifecycleOwner, { notes -> noteAdapter.submitList(notes) }
        )

DiffUtil and Adapter

 private inner class DiffCallback : DiffUtil.ItemCallback<NoteEntity>() {
        override fun areItemsTheSame(oldItem: NoteEntity, newItem: NoteEntity): Boolean {
            return oldItem.id == newItem.id
        }

        override fun areContentsTheSame(oldItem: NoteEntity, newItem: NoteEntity): Boolean {
            return oldItem == newItem
        }
    }

    private inner class NoteAdapter :
        ListAdapter<NoteEntity, NoteHolder>(DiffCallback()) {

        override fun getItemCount(): Int {
            return super.getItemCount()
        }

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): NoteHolder {
            val view = layoutInflater.inflate(R.layout.list_item_note, parent, false)
            return NoteHolder(view)
        }

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

I have been looking for a solution to the problem for a long time, but I could not understand what the reason is

sorry for my bad english, it's not my native language

You have to delete that item from the dataset and submit it again on your `ListAdapter` instance — Kapta, May 01 '21 at 04:47
@Zain no, because liveData observer notify RV about changes automatically — kivinus, May 01 '21 at 07:19
Yes, you're right just was in a doubt that was a potential reason of your issue — Zain, May 01 '21 at 10:52

score 2 · Accepted Answer · answered May 01 '21 at 07:38

2

I had the same exact problem and it was caused by using wrap_content for RecyclerView in your xml file.

Because you delete an item, the size of this view changes, and for a split second you can see this weird behaviour. To fix that, make sure that the RecyclerView occupies the whole screen - its height is set to match_parent and the container it is in is also set to match_parent.

answered May 01 '21 at 07:38

baltekg

985
9
31

1

Nice answer! .. Apart from the issue, using `wrap_content` for `RecyclerView` is not a good practice int terms of performance as it has new calculations for the entire list of the `RecyclerView` whenever adding/removing rows and this makes it lose its main feature for recycling views in this case – Zain May 01 '21 at 10:49
1

That is a valid point Zain. I am just wondering if `wrap_content` would cause trouble if `hasFixedSize` is set to true? From my understanding if `wrap_content` is a necessity in some case, setting this flag to true might help with performance issues caused by using `wrap_content`. – baltekg May 03 '21 at 16:59
Nice catch indeed.. [this answer](https://stackoverflow.com/questions/28709220/understanding-recyclerview-sethasfixedsize#59033210) has a clue, but I think you need to test it your self with a simple example, you could extend the `layoutManger` and debug it to see which methods can be called in either case – Zain May 03 '21 at 21:58

score 0 · Answer 2 · answered May 01 '21 at 07:26

0

Sorry. Strange behavior was not caused by the adapter but by xml. Height of the layout was set as wrap_content and after removing the item size of RV changed which caused the wrong behavior.

answered May 01 '21 at 07:26

kivinus

15
2

RecyclerView(DiffUtil+ListAdapter) strange behavior after delete item

2 Answers2