onBindViewHolder of RecyclerView inside nestedscrollview is getting invoked for all item at once - android-fragments

Question

I am having a CollapsingToolbar and a bottom navbar as shown:
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:fitsSystemWindows="true"
app:layout_constraintBottom_toTopOf="#id/nav_view"
app:layout_constraintTop_toTopOf="parent">
<!-- Scrollable view here -->
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appBar"
android:layout_width="match_parent"
android:layout_height="#dimen/height335"
android:background="#drawable/ic_appbar_bg"
android:fitsSystemWindows="true"
app:elevation="0dp">
<com.google.android.material.appbar.CollapsingToolbarLayout
android:id="#+id/collapsingToolbar"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
app:contentScrim="#color/colorPrimaryDark"
app:toolbarId="#+id/toolbar"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#android:color/transparent"
android:contentInsetStart="0dp"
android:contentInsetLeft="0dp"
android:gravity="center"
app:contentInsetEnd="0dp"
app:contentInsetEndWithActions="0dp"
app:contentInsetLeft="0dp"
app:contentInsetRight="0dp"
app:contentInsetStart="0dp"
app:contentInsetStartWithNavigation="2dp"
app:layout_collapseMode="pin"
app:theme="#style/ToolbarTheme">
<include
android:id="#+id/toolbar_header_view"
layout="#layout/widget_header_view_top"
android:layout_width="match_parent"
android:layout_height="wrap_content"
bind:cardDetails="#{viewModel}" />
</androidx.appcompat.widget.Toolbar>
<include
layout="#layout/widget_header"
bind:cardDetails="#{viewModel}" />
</com.google.android.material.appbar.CollapsingToolbarLayout>
</com.google.android.material.appbar.AppBarLayout>
<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
android:id="#+id/swipe"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<!-- just a nestedscrollview
override fun onTouchEvent(ev: MotionEvent): Boolean {
return scrollable && super.onTouchEvent(ev)
}
override fun onInterceptTouchEvent(ev: MotionEvent): Boolean {
return scrollable && super.onInterceptTouchEvent(ev)
}
fun setScrollingEnabled(enabled: Boolean) {
scrollable = enabled
} -->
<com.android.utils.LockableNestedScrollView
android:id="#+id/nestedScrollView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
android:clipChildren="false"
android:clipToPadding="false"
android:fillViewport="true">
<LinearLayout>
<Some views...
<androidx.fragment.app.FragmentContainerView
android:id="#+id/nav_host_fragment"
android:layout_width="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
android:layout_height="match_parent" />
</LinearLayout>
</com.android.utils.LockableNestedScrollView>
</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/add"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="#{()->viewModel.fabClicked()}"
android:src="#drawable/ic_plus"
app:fabCustomSize="#dimen/fab70"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1" />
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="#+id/nav_view"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginEnd="0dp"
android:background="?android:attr/windowBackground"
android:elevation="#dimen/elevation3"
android:paddingTop="#dimen/padding10"
app:itemTextAppearanceActive="#style/BottomNavigationViewTextStyle"
app:itemTextAppearanceInactive="#style/BottomNavigationViewTextStyle"
app:labelVisibilityMode="labeled"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:menu="#menu/nav_view" />
Fragment container will be replaced with fragments when nav bar items are clicked. The issue is that in one of the fragment I have a recyclerview. The onBindView of all the items in the recyclerview is getting invoked all at once. I need to avoid this mainly because I am trying to implement Pagination like this:
override fun onBindViewHolder(holder: TopUpViewHolder, position: Int) {
val item = myDataset[position]
holder.bind(item)
if (position == this.itemCount - 1){
// do your load more task here
viewModel.fetchTopUpData()
}
}
(I tried attaching scroll listener and implement pagination like this. But the canScrollVertically(1) is getting invoked even when the user has not reached the end, probably because of nestedscrollview itself.)
Here is my fragment with recyclerview:
<?xml version="1.0" encoding="utf-8"?>
<data>
<import type="android.view.View" />
<variable
name="viewmodel"
type="com.android.ui.topup.viewmodel.TopUpViewModel" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:clipToPadding="false"
android:padding="#dimen/padding15">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:clipToPadding="false"
android:orientation="vertical">
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/status_header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="#dimen/padding20"
android:visibility="#{viewmodel.headerVisibility}">
<TextView
android:id="#+id/recentLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="#dimen/margin20"
android:text="#string/recent_top_ups"
android:textAllCaps="true"
android:textColor="#color/topup_label_text_color"
android:textSize="#dimen/text12"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/viewAll"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="#dimen/margin20"
android:onClick="#{()->viewmodel.viewAllClicked()}"
android:text="#string/view_all"
android:textColor="#color/topup_label_color_orenge"
android:textSize="#dimen/text14"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/topUpRCView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:nestedScrollingEnabled="false"
android:clipChildren="false"
android:clipToPadding="false"
app:scrollListener="#{viewmodel.scrollListener}" />
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:visibility="#{viewmodel.fetchingFlag?View.VISIBLE:View.GONE}" />
</LinearLayout>
<LinearLayout
android:id="#+id/empty_list"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="#{viewmodel.listEmpty}"
android:orientation="vertical">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:src="#drawable/ic_illustration_receipt"/>
<TextView
android:id="#+id/empty_list_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/you_have_no_topup_requests"
android:fontFamily="#font/colfaxregular"
android:textColor="#333547"
android:layout_marginTop="36dp"
android:textSize="#dimen/text16"
android:alpha=".3"/>
</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
Things that I have tried:
Added android:nestedScrollingEnabled="false" in the recyclerview
Added app:layout_behavior="#string/appbar_scrolling_view_behavior"
Changed the height of recyclerview to match_parent wrap_content also 0 and set layout weight as 1(RCV is inside a linearlayout)
https://stackoverflow.com/a/44470106/6341943 => adding a header viewholder for some reason
https://stackoverflow.com/a/37558761/6341943 => cant do this because, I have a bottomnavbar
Now for the Weird part
If I keep my fragment inside a viewpager, for some reason the issue is not happening. (Even this hack is not usable is because it's messing up my collpsingToolbarLayout)

Answer 1

I have wasted at least a week behind this and the only solution that works is to remove the nestedscrollview. To make the recyclerview to actually recycle the view, you HAVE TO REMOVE the nestedscrollview. If you happen to have multiple views inside instead of just the recyclerview, You have to add them as items of the recyclerview by setting different viewholders, and then adding
app:layout_behavior="#string/appbar_scrolling_view_behavior"
to the recyclerview or the parent of recyclerview(the parent cannot have any other view other than Recyclerview for this to work).
In my case, the requirement was as follows:
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:fitsSystemWindows="true"
app:layout_constraintTop_toTopOf="parent">
<!-- Scrollable view here -->
<com.google.android.material.appbar.AppBarLayout
.... >
<com.google.android.material.appbar.CollapsingToolbarLayout
....>
<androidx.appcompat.widget.Toolbar
....>
<include
android:id="#+id/toolbar_header_view"
.... />
</androidx.appcompat.widget.Toolbar>
<include layout="#layout/widget_header" />
</com.google.android.material.appbar.CollapsingToolbarLayout>
</com.google.android.material.appbar.AppBarLayout>
<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
....>
<LinearLayout orientation="vertical" ....>
<View .../> <!-- I needed to have these two views along with recyclerview and i wanted them to do nestedscroll along with recyclerview -->
<View .../>
<androidx.recyclerview.widget.RecyclerView
.... />
</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
I needed to have two views before recyclerview and I wanted them to do nestedscroll along with recyclerview. The only thing that worked was by removing these to views and adding them as the first two items of recyclerview, and then adding
app:layout_behavior="#string/appbar_scrolling_view_behavior"
to the swipetorefresh layout
Hope this helps someone. I will add more info If required.