Develop Reference

Switching between using multiple adapters for a single recyclerview

Can I utilize multiple adapters for my recyclerview wherein I can switch between using one of them to populate my recyclerview?
That is given adapter A populating my recyclerview,I can stop it and use adapter B to repopulate the recyclerview.

Yes.
Just use RecyclerView.setAdapter(adapter) with the new adapter

Multiple LayoutManager in ConcatAdapter

I want to implement an ConcatAdapter like this image:
This page's recyclerView contains these elements:
Title
Horizontal recyclerView (with pagination)
Title
Vertical recyclerView (no pagination)
Title
Horizontal recyclerView (with pagination)
But the problem is I can set only one LayoutManager to recyclerView that holds ConcatAdapter as I know.
How can set different layoutmanager to each adapter?
Or any other solution to implement this page with CocantAdapter?
(Why ConcatAdapter? Because it sovle performance prblems of nestedRecyclerView even with recyclerViewPool as I know)

This unfortunately is not possible. A RecyclerView adapter is just a component to provide and bind views for each row. A ConcatAdapter is no different, it just redirects from the individual adapters.
If it did have any control over the layout managers it would really defeat the entire point of the modularity of RecyclerView, which is what makes it so powerful in the first place.
You can take a look at the source code here to find out more about how it is implemented.

Simple solution is to create a Viewpool in the Activity/Fragment.
The Adapter for the recyclerview has 2 different types of items,
The regular one and the other that actually has a recyclerview with the horizontal layout as Adapter in it.
So a Viewholder that holds a recyclerview inside with its own viewholders.
Then you just grab the created viewpool from the activity to assign it as the shared Pool to all of the adapters with the horizontal scroll, thats it :-)
Concat Adapter doesnt help with this im afraid so this would be my alternative solution

Is it okay to do the RecyclerView setAdapter() several times?

When use RecyclerView, Does it matter how many times setAdapter() has been used?
Or should setAdapter be used only once?
and Is it okay to use setAdapter after adding items to the adpater?
Or should the setAdapter work before adding items to the adapter?

General practise is to call RecyclerView::setAdapter once per instantiation of the RecyclerView then use the RecyclerView.Adapter<VH> for updating the underlying List<T> data set then calling methods like Adapter::notifyDatasetChanged.
Recyclerview.Adapter also allows updating individual rows through other methods : https://developer.android.com/reference/androidx/recyclerview/widget/RecyclerView.Adapter
More modern techniques include DiffUtil or AsyncListDiffer which uses DiffUtil or manual implementations to abstract working out individual row changes between data set updates. This is the most efficient mechanism as it only needs to "rebind" changed data on screen, rather than rebinding all views.
If you intend to change the type T of the underlying data set then you can call RecyclerView::setAdapter more than once, as you are fundamentally changing the adapter data set type. This however is an edge case.

Unless you are switching different adapters on the same RecyclerView, it's recommended you call setAdapter once (even with an empty list of elements). Then, when you update the list of elements, you can call adapter methods like notifyDataSetChanged and other similar methods.

Well, if you are setting the same adapter instance multiple times just to refresh then, please take a look at RecyclerView.Adapter#notifyDataSetChanged()
A better approach would be 'setAdapter work before adding items to the adapter' and then you can add, remove, and modify adapter data items. Then you can notify the adapter.

Why recyclerview is faster than listview [duplicate]

This question already has answers here:
Android Recyclerview vs ListView with Viewholder
(7 answers)
Closed 3 years ago.
I was reading about the difference b/w recyclerview and listview and found out that recyclerview is faster than listview.
I tried to search online but not found any satisfactory answer I know it is used ViewHolder pattern and Notifying adapter but what does it does intearlly so it is faster?

Recycler View you could say is an efficient way to create list of views.
If you have 1000 items like ur contact list , and If ur visible screen can show only 10 items at once, it will Create only 10+1 (or +2) Views and as u scroll , items/views that left will be reused (not create) to show new data.
Recycler View by default does this, where as List View by default doesn't do.

There are some differences between these two views.
ListView is a bit heavy and it has a lot of responsibilities. Whenever we have to handle the list, such as to configure it in some way, the only way to do this is through the ListView object or inside the adapter.
A lot of bad things in the ListView were fixed or changed in the RecyclerView. It’s more efficient by default, the layout is separated and we have more possibilities over the data set inside the adapter.
These are some crucial differences between ListView and RecyclerView:
1 ViewHolder
The ViewHolder pattern allows us to make our list scrolling act smoothly. It stores list row views references and, thanks to this, calling the findViewById() method only occurs a couple of times, rather than for the entire dataset and on each bind view.
The RecyclerView’s adapter forces us to use the ViewHolder pattern. The creating part (inflating the layout and finding views) and updating the views is split into two methods — onCreateViewHolder() and onBindViewHolder().
The ListView, on the other hand, doesn’t give us that kind of protection by default, so without implementing the ViewHolder pattern inside the getView() method, we’ll end with inefficient scrolling in our list.
2 LayoutManager
The LayoutManager takes responsibility for layouting row views. Thanks to this, RecyclerView doesn’t have to think about how to position the row view. This class gives us the opportunity to choose the way that we want to show the row views and how to scroll the list. For example, if we want to scroll our list vertically or horizontally, we can choose LinearLayoutManager. For grids, it is more suitable to choose the GridLayoutManager.
Previously, with the use of the ListView, we were only able to create a vertical-scrolling list, so it wasn’t that flexible. If we wanted grids on our list, we had to choose the other widget for that — GridView.
3 ItemDecoration
A duty of the ItemDecoration is simple in theory – add some decorations for the list row views – but in practice, it’s that simple to implement if we want to create a custom one. In this case, we should extend the ItemDecoration class and implement our solution. For example, the RecyclerView list has no dividers between rows by default and it’s consistent with the Material Design guidelines. However, if we want to add a divider for some reason, we can use DividerItemDecoration and add it to the RecyclerView. In case we use the ListView, we have to figure out rows decorations by ourselves. There is no helper class like ItemDecoration for this widget.
4 ItemAnimator
The last but not least component of RecyclerView that I want to mention is ItemAnimator. As we can expect, it’s handling row views animations like list appearance and disappearance, adding or removing particular views and so on. By default, RecyclerView’s list animations are nice and smooth. Of course, we can change that by creating our own ItemAnimator, which is also not that easy. To make it easier, we should extend the SimpleItemAnimator class and implement the methods that we need (just add animations to a ViewHolder’s views). To be honest, implementing animations on the ListView was a pain. Again, we had to figure out how we want to handle them.
5 Notifying adapter
We have a couple of cool notifiers on the RecyclerView’s adapter. We are still able to use notifyDataSetChanged() but there are also ones for particular list elements, like notifyItemInserted(), notifyItemRemoved() or even notifyItemChanged() and more. We should use the most appropriate ones for what is actually happening, so the proper animations will fire correctly.
Using ListView, we were able to use just notifyDataSetChanged() on the adapter and then had to handle the rest ourselves, again.

Because of ViewHolder Pattern.
Thats was the simplest answer. Now for some details.
What recycler view does is what it's name indicates "Recycle", yes it recycles items, and it does it with the help of ViewHolder Pattern.
By Using ViewHolder we do-not need to call findViewByID() every time we go through getView()method. The reference for all rows are stored in-memory. This increases the performance significantly, as findViewByID()is a heavy process.
Hope this clears your confusion.

RecyclerView with different Cardview that hold other list in them

I have a recyclerView with two cardView one with plain text and the other with a list of data which is not specified. I have no problem creating two different view holder and set one single text data on first. The problem is how to load a list inside the 2nd cardView. Is it possible to create a list view adapter inside a recyclerView adapter ??

You should implement Custom LayoutManager for that. Refer this answer for an example and explanation of how to do that

Please post your code so that we can better understand your issue.
You can place a recycler view inside the second card view. And you can override getItemViewType() in adapter to handle the two card views.