Develop Reference

Android recycler view update

I have a recycler view with a delete button for every item,and the data for the recycler view is a Live Data list.
Basically im observing the list and when i delete an item i just pass the adapter again to the recycler view with the new list in order for the list to update,like this
viewModel.loadBasketItems().observe(viewLifecycleOwner, {
adapter = BasketFragmentAdapter(it, viewModel, requireContext())
recycler.adapter = adapter
})
My first problem with this is that the image jumps to the top of the list every time i delete an item,because the list is created again completely
My second problem with this is i don't think this is very efficient.
What's the best method to update the recycler view after you change something

You shouldn't be resetting the adaptor like that. Keep the adaptor the same, but call notifyDataSetChanged(). This tells the adaptor its data has changed, which will tell the recycler view to redraw itself. What you're doing makes the recycler view assume it has a whole new adaptor and needs to drop all info about the old one.
Even better would be to call one of the more specific notify functions on the adapter that tell it what elements changed, but the general one is good enough until you see perf issues.

Get ListView item position by uri / by the data it contains

I have a ListView which I populate using a custom CursorAdapter.
Now I want to manually update just one specific item in the ListView. I have the content URI of that item. Is it possible to use just this info to get the position of the item in the listView?
If I have the position I can do something like
View v = mListView.getChildAt(itemPosition - mListView.getFirstVisiblePosition());
to update the view. But how can I get itemPosition?
I know that I get the position in the onItemClickListener, but I need to update the view without it being clicked.
Any help guys?

ListView does not support updating a single position.
You must update the adapter with the new data (even if you change a single position) and the, invoke mAdapter.notifyDataSetChanged()
If you get the View by its position (via listView.getChildAt()) will work. However, if you scroll up and down the list, that view will display the old data again because the adapter is not aware of the change (and it is the adapter which update the view contect view getView()).
When you invoke notifyDataSetChanged(), you are telling to the adapter that your data set has new info and the ListView/Adapter will re-draw the visible items (it won't re-draw whole list at once.. only the visible items).
You may want to consider to change to RecyclerView in the future. The BaseAdapter used in a RecyclerView support actions such as add/remove/update a single position.

NotifyDataSetChanged refreshes RecyclerView but scrolls as well.

I have a RecyclerView and one item row needs to be updated like every second (SeekBar). So I call NotifyDataSetChanged once I update the data in the list. UI gets updated but the issue is that the RecyclerView scrolls so that this particular item is either at top or bottom of the screen.
I don't want RecyclerView to scroll.
// Update Data
mData.set(mData.indexOf(cardData), cardData);
// RefreshView
refreshView() {
runOnUiThread(new Runnable(){
notifyDataSetChanged();
}
);

You can update one item using notifyItemChanged(position); and u wont update all data in adapter, you will update only certain item

It's better to use the other notify methods from the RecyclerView.
For your usecase only swap out one item in your Adapter instead of all items and use notifyItemChanged(position).
This will be faster, the View won't scroll and if you ever will add an animation this will only work if you don't use notifyDataSetChanged

I got it working. I was having a card view above the recycler view.I just removed it. Now the whole screen is a recyclerView and I cannot see any auto scrolls.

How to refresh a list view item without scrolling it off screen

I'm using adapter.notifyDataSetChanged(). I'm just curious if I can refresh a list view item without scrolling it off screen when call that method.

adapter.notifyDataSetChanged() will automatically call getView() for every row currently at least partially visible on the screen.
You don't have to scroll anything.

From the official documentation
notifyDataSetChanged(): Notifies the attached observers that the underlying data has been changed and any View reflecting the data set should refresh itself.
So, in other words , whenever you call that method, is being called the getView() method and refresh the content of your changed slots.

Nested RecyclerView scrolls to the first item on NotifyItemChanged

I have vertical RecyclerView for scrolling group of items and horizontal RecyclerView in each ViewHolder in order to scrol items inside of these groups. They are populated from database. Whenever item content is changed (user tap something or new data come from network) it is written to database and then notifyDataSetChanged() is called for the group cursor. I check if it is the same group in onBingViewHolder() and update items only if it is. But horizontal RecyclerView is scrolled anyway to the first item.
How could I prevent this behavior and why does it happens ?
BTW I'm writing result of this check in 'onBindViewHolder()` to the log and I can see that it is the same item.
Thanks.

RecyclerView creates new ViewHolder in order to perform animation. setItemAnimator(null) solved my problem.