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BottomSheetBehavior with ViewPager2 can't be scrolled down by nested RecyclerView scroll

I have a view that acts like BottomSheetBehavior and this view has ViewPager2 inside. Each ViewPager2's page is a vertical RecyclerView. The issue is that BottomSheet doesn't scroll down when current vertical RecyclerView (which is a page of ViewPager) can't scroll vertically anymore. Everything works file when instead of ViePager I have only one vertical RecyclerView.
The temporary solution is to wrap ViewPager with NestedScrollView but it's horrible for performance and has it's own bugs.
The original layout:
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/core"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#C7C7C7"
tools:context=".MainActivity">
<LinearLayout
android:id="#+id/bottom_sheet"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FFFFFF"
android:elevation="8dp"
android:orientation="vertical"
app:behavior_hideable="true"
app:behavior_peekHeight="300dp"
app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior">
<com.google.android.material.tabs.TabLayout
android:id="#+id/tab_layout"
android:layout_width="wrap_content"
android:layout_height="24dp"
android:layout_gravity="center_horizontal"
app:tabGravity="center"
app:tabMode="scrollable" />
<androidx.viewpager2.widget.ViewPager2
android:id="#+id/view_pager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
[Here's how it looks (sorry for the gif quality)]

I've found a solution for this case, I set isNestedScrollingEnabled = false for inner RecyclerView so that BottomSheetBehavior finds another scrolling view
viewPager.children.find { it is RecyclerView }?.let {
(it as RecyclerView).isNestedScrollingEnabled = false
}

BottomSheetBehaviour only detects the first scrollable view. So it is always recommended to use only one scrollable view inside of it.
For More information check this answer bottomsheetbehavior-with-two-recyclerview
And this one also Scroll not working for multiple RecyclerView in BottomSheet
If you really want to have the two scrollable views I recommend you to take a look at this library also AndroidSlidingUpPanel

How to scroll whole activity

I wrote an application and home page is LinearLayout and is in Fragment. In this LinearLayout there are two RecyclerViews and SearchBar etc. I want to scroll whole activity. I spent 2 days for it but cannot succeed. How can I do that in easy way? There are lots of adapters and connections in that LinearLayout. How can I achieve that without broke any code.
I want to scroll whole activity.
Thanks in advance.

Set Scroll/NestedScrollView as a parent view in xml to scroll whole layout.
Add below attribute in recycler view to stop recycler scroll:
android:overScrollMode="never"
Try below code:
<android.support.v4.widget.NestedScrollView
android:id="#+id/navigation_nested"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true"
android:overScrollMode="never">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="#dimen/margin_15">
<TextView
android:id="#+id/video_tv"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="#dimen/margin_15"
android:drawableLeft="#drawable/ic_video_tutorial"
android:drawablePadding="#dimen/margin_20"
android:fontFamily="#font/poppins"
android:paddingLeft="#dimen/text_15"
android:text="#string/videos"
android:textColor="#color/blackTextColor"
android:textSize="#dimen/text_15" />
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:overScrollMode="never" />
</LinearLayout>
</android.support.v4.widget.NestedScrollView>

You just add this line:
//java
yourRecyclerView.setLayouManager(new LinearLayoutManager(this));
//kotlin
yourRecyclerView.layoutManager = LinearLayoutManager(this)
or from xml:
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
Notice that there is not only LinearLayoutManager. If you are using a Grid RecyclerView than you might want to use GridLayoutManager

I solved the problem.
Just write ScrollView over the LinearLayout
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout>
.....
</LinearLayout>
</ScrollView>

Paging library when used inside a nestedscrollview loads all data

I am using paging library to load data and populate my recyclerview which is placed inside a nestedscrollview. But it is like, pagination works automatically until all the data fetched from API. I know this is because of the nestedscrollview. But unfortunately my layout needs scrollview as i have a top section other than recyclerview in this fragment.
This is my layout
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true"
>
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
//have a layout here which scrolls with recyclerview
<Recyclerview />
</ConstraintLayout>
</NestedScrollView>
Everything works fine when i do not use nestedscrollview. There is an open issue in googlesamples git repo regsrding this problem.
https://github.com/googlesamples/android-architecture-components/issues/215
Is anyone have idea how can we implement pagination when a recyclerview is inside a scrollview with pagination library from Android jetpack. I know we can implement traditional kind of pagination attaching listener to nestedscrollview, but i am looking to implement pagination with architecture component library.
https://developer.android.com/topic/libraries/architecture/paging/

Using the below code will solve the issue.
Here is the view hierarchy:
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:id="#+id/coordinator_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appbar_layout"
android:background="#color/white"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.google.android.material.appbar.CollapsingToolbarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_scrollFlags="scroll|exitUntilCollapsed"
app:titleEnabled="false">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<!-- Put here elements that you need above the recycler view -->
</LinearLayout>
</com.google.android.material.appbar.CollapsingToolbarLayout>
</com.google.android.material.appbar.AppBarLayout>
<!-- RecyclerView -->
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:nestedScrollingEnabled="true"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
android:scrollbars="vertical"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
Note: Be sure that you have given id to CoordinatorLayout and AppBarLayout so that it will retain scroll position on the back stack.

The problem is recyclerview inside nested scrolview. Paging library has nothing to do with it. The behavior would be same if you try to load data on scroll listener of recyclerview.

The paging library does not work well with nestedScroolView. So you have to change your NesteScrollView to ScroolView with android:nestedScrollingEnabled="true", something like this:
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:nestedScrollingEnabled="true"
>
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
//have a layout here which scrolls with recyclerview
<Recyclerview />
</ConstraintLayout>
</ScrollView>

RecyclerView containing CardView's won't scroll (not in focus?) unless after clicked once

My RecyclerView contains a list of CardView
xml for MainActivity:
<android.support.design.widget.CoordinatorLayout>
<android.support.design.widget.AppBarLayout>
<android.support.v7.widget.Toolbar/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.widget.NestedScrollView>
<android.support.v7.widget.RecyclerView
android:id="#+id/view_recycler"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
</android.support.v7.widget.RecyclerView>
</android.support.v4.widget.NestedScrollView>
<FloatingActionButton/>
</android.support.design.widget.CoordinatorLayout>
I use an adapter for the RecyclerView above to contain the Cards.
xml used to inflate ViewHolder inside the adapter:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/relativeLayout"
android:paddingTop="2dp"
android:paddingRight="2dp"
android:paddingLeft="2dp"
android:orientation="vertical"
android:descendantFocusability="blocksDescendants">
<android.support.v7.widget.CardView
android:id="#+id/cardview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:foreground="?android:attr/selectableItemBackground"
card_view:cardBackgroundColor="#android:color/holo_red_light"
card_view:cardPreventCornerOverlap="true"
card_view:cardCornerRadius="2dp"
card_view:cardElevation="3dp"
card_view:contentPadding="7dp"
card_view:cardUseCompatPadding="true">
<RelativeLayout
android:id="#+id/relat"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:focusable="true"
android:focusableInTouchMode="false"
android:padding="10dp">
<TextView/>
//...
</RelativeLayout>
</android.support.v7.widget.CardView>
</RelativeLayout>
To make the Cards clickable, I tried all solutions in these - two popular posts , but I always have this weird bug:
The list of Cards won't scroll when I start the app for the first time, unless I click on the RecyclerView once. It's as if the RecyclerView is not in focus initially.
Also, if I get rid of all click listeners or similar ways to make the CardView's clickable, and only keep the focusable code in xml:
android:focusable="true"
android:focusableInTouchMode="false"
, then it does scroll right away, but as soon as I add any click (listener) mechanism, or even include "android:clickable="true"" for the ViewHolder, that bug re-emerges.
Please advise. Thank you

You should never nest a RecyclerView inside a ScrollView. Just remove the NestedScrollView and the RecyclerView should take care of its scrolling behavoiur.
<android.support.design.widget.CoordinatorLayout>
<android.support.design.widget.AppBarLayout>
<android.support.v7.widget.Toolbar/>
</android.support.design.widget.AppBarLayout>
<android.support.v7.widget.RecyclerView
android:id="#+id/view_recycler"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
</android.support.v7.widget.RecyclerView>
</android.support.design.widget.CoordinatorLayout>

Turns out the scrolling issue is not related to the RecyclerView. It was due to an open source widget I used which anchored to the RV and somehow interfered with the focusing/scrolling/touch interception. Finally got rid of this bug after days of looking elsewhere..
thank you all the same

RecyclerView inside NestedScrollView onBindViewHolder calling for all getItemCount size

When I put RecyclerView inside NestedScrollView then onBindViewHolder is calling for all row like say I have list which has size of 30 then onBindViewHolder is called for all 30 rows at one time even without scrolling
RecyclerView list;
LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
list.setLayoutManager(layoutManager);
layoutManager.setAutoMeasureEnabled(true);
list.setNestedScrollingEnabled(false);
list.addItemDecoration(new VerticalSpaceItemDecoration(5));
list.setAdapter(adapter);
my xml is
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fillViewport="true"
android:scrollbars="none"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/grey">
<android.support.v7.widget.RecyclerView
android:id="#+id/recycler_views"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#+id/info"
android:layout_marginBottom="5dp"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:textAlignment="center"
android:visibility="visible"
/>
but if I remove NestedScrollView it's working properly.

I'm going to assume that since your are using appbar_scrolling_view_behavior you are trying to do something with AppBarLayout.
If so, you can use RecyclerView as a direct child of CoordinatorLayout and have support for AppBarLayout scrolling without nesting RecyclerView inside of NestedScrollView.
Try this: RecyclerView inside CoordinatorLayout (with AppBarLayout and CollapsingToolbarLayout):
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fitsSystemWindows="true">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsing_toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_scrollFlags="scroll">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="80dp"
android:background="#55FF00FF"
app:layout_collapseMode="none"/>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<android.support.v7.widget.RecyclerView
android:id="#+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
</android.support.design.widget.CoordinatorLayout>
And in your Activity or CustomView:
RecyclerView list;
LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
list.setLayoutManager(layoutManager);
list.addItemDecoration(new VerticalSpaceItemDecoration(5));
list.setAdapter(adapter);

But you set android:layout_height for NestedScrollView to wrap_content - here, it's zero by default (because there no content for him at the moment of the declaration). Next, for RecyclerView you set android:layout_height to match_parent - which is at the moment is 0. Thus, all your items have 0 height.
Thus, you have such situation.
Solution: use solution above from #dkarmazi https://stackoverflow.com/a/37558761/3546306 or try to change parameter android:layout_height values.

It's right.Because you are using a ScrollView.ScrollView is not recyclable like RecyclerView or ListView.It will show all view contains these out of screen in one time.You should use a other layout instead.

I faced the same issue. After a bit of research fount the solution.
You need to make sure your recyclerview height is fixed by setting it to MATCH_PARENT. Or if its in a contraint layout then set height to 0dp and set the required height constrains.
Then set recyclerview.setHasFixedSize to true.
The onBindViewHolder will start getting called after this.