Reyclerview Isn't Working

ReyclerView isn't working

You should return the size of your data ArrayList in getItemCount()

Use this:

@Override
public int getItemCount() {
    return data.size();
}

Instead of this:

@Override
public int getItemCount() {
    return 0;
}

selection not working in reyclerview item in android

Your adapter never reads from selectedItemPosition, so how could it ever change which item is shown as selected?

By using the defaultValue from the list items every time you bind the items, they will never be able to change either.

To simplify this, let your adapter treat selectedItemPosition as the single source of truth about what should be selected. The Activity should tell it which item to start with:

val selectionAdapter = SelectionAdapter()
val list = createList()
selectionAdapter.selectedItemPosition = list.indexOfFirst { it.defaultValue == true }
selectionAdapter.submitList(list)

Your adapter should exclusively use selectedItemPosition as its source for whether an item should appear selected. And the click listener only needs to change the selected item. It's pointless to have it change the item's appearance manually because this can only briefly change how it looks until the next time the view holder is bound.

override fun onBindViewHolder(holder: SelectionViewHolder, position: Int) {
    holder.binding.root.setOnClickListener {
        selectedItemPosition = holder.adapterPosition
    }
    holder.bindItem(getItem(position), selectedItemPosition == position)
}

inner class SelectionViewHolder(val binding: SelectionItemLayoutBinding) :
    RecyclerView.ViewHolder(binding.root) {

    fun bindItem(item: MainActivity.Data, isSelected: Boolean) = with(binding) {
        textView.text = item.value
        root.isSelected = isSelected
    }
}

RecyclerView EmptyView has RecyclerItem

I find out one issue, in your empty adapter, your code

@Override
    public int getItemCount() {
        return 0;
    }

so nothing be show, if you want show your empty text, please using

@Override
        public int getItemCount() {
            return 1;
        }

RecyclerView doesn't set adapter

you forgot to set size in your adapter:-

@Override
    public int getItemCount() {
        return mDataset.size();
    }

Recycler View Not Showing Items

You're returning zero for the itemCount, therefore your adapter thinks you don't have any items. Try this in your adapter:

@Override
public int getItemCount() {
    return itemList.size();
}

ViewPager2 not working with RecyclerView.Adapter

change return type in ImagesViewerFragment.java to

return fragmentImagesViewerBinding.getRoot();

Firebase ReyclerView adapter not displaying on activity start

you need to use the messageAdapter.notifyDataSetChanged(); inside the indide the firebase request not outside it cause it's asynchrone so firebase doesn't block the main thread until it finish

ListAdapter not updating item in RecyclerView

Edit: I understand why this happens that wasn't my point. My point is that it at least needs to give a warning or call the notifyDataSetChanged() function. Because apparently I am calling the submitList(...) function for a reason. I am pretty sure people are trying to figure out what went wrong for hours until they figure out the submitList() ignores silently the call.

This is because of Googles weird logic. So if you pass the same list to the adapter it does not even call the DiffUtil.

public void submitList(final List<T> newList) {
    if (newList == mList) {
        // nothing to do
        return;
    }
....
}

I really don't understand the whole point of this ListAdapter if it can't handle changes on the same list. If you want to change the items on the list you pass to the ListAdapter and see the changes then either you need to create a deep copy of the list or you need to use regular RecyclerView with your own DiffUtill class.

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