Develop Reference

RecyclerView notifyDataSetChange scroling all the way up, not working as i want it to

I am writing a photo picker for Facebook inside my app, i have a recyclerview with a grid layout and i want to prevent for scrolling up, i was able to do this by using scrollToPosition and this works but not the way i want
Problem
When i click in a photo on the 2 row that row jumps to the top and becomes the number 1 visible row, if i click the 3 row the samething happens.
I don't want the recycler to move if the view is visible it should remain the same, so if i click on a a photo that is on the last visible row i want the scroll to stay the same, i don't want it to make the last row the first.
Tries to solve it
I tried several things to fix this, i tried calling setNestedScrollingEnabled i followed this How to disable RecyclerView scrolling?
public static void onItemClick(int position){
//picker.setNestedScrollingEnabled(false);
for(int k = 0; k<photoBag.size();k++) {
if(k == position)
photoBag.set(position, new PhotoBag(photoBag.get(position).getPhoto(), true)); //Here im marking the photo to selected
else
photoBag.set(k, new PhotoBag(photoBag.get(k).getPhoto(), false));//Here im setting unselecting all the other photos
}
picker.setAdapter(adapter);
adapter.notifyDataSetChanged();
picker.scrollToPosition(position);
//Log.d("FacebookPicker", "position " + grid.findFirstCompletelyVisibleItemPosition());
//picker.setNestedScrollingEnabled(true);
}
I thought that maybe disabling the scroll would lock the recyclerview on the corrent position but it didn't jumps right up.
I also tried getting the Vertical offset and set it after calling notifyDataSetChange but i can't find a way to set the offset programmatically
EDIT
Adapter
class PickerAdapter extends RecyclerView.Adapter<PickerAdapter.PickerAdapterHolder> {
public final String TAG = "PickerAdapter";
private ArrayList<PhotoBag> photoBag;
private Context context;
private OnClickListener onClickListener;
class PickerAdapterHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
ImageView photo;
ImageView imageBorder;
PickerAdapterHolder(View view) {
super(view);
photo = (ImageView) view.findViewById(R.id.photoItem);
photo.setOnClickListener(this);
}
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.photoItem:
FacebookPhotoPicker.onItemClick(getAdapterPosition()); //i know that there are better ways to get the clicked item from other class but since im still debuging i don't need to worry about performace i just need it to work
break;
}
}
}
PickerAdapter(Context context, ArrayList<PhotoBag> itemList) {
this.photoBag = itemList;
this.context = context;
}
#Override
public PickerAdapterHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View layoutView = LayoutInflater.from(parent.getContext()).inflate(R.layout.facebook_picker_item, null);
return new PickerAdapterHolder(layoutView);
}
#Override
public void onBindViewHolder(final PickerAdapterHolder holder, final int position) {
if(photoBag.get(position).isSelected()){
int border = Math.round(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 5, context.getResources().getDisplayMetrics()));
Bitmap photo = photoBag.get(position).getPhoto();
photo = Bitmap.createScaledBitmap(photo,photo.getWidth() - (border*2), photo.getHeight() - (border*2), false);
photo = addWhiteBorder(photo,border);
holder.photo.setImageBitmap(photo);
}else {
holder.photo.setImageBitmap(photoBag.get(position).getPhoto());
}
}
#Override
public int getItemCount() {
return this.photoBag.size();
}
private Bitmap addWhiteBorder(Bitmap bmp, int borderSize) {
Bitmap bmpWithBorder = Bitmap.createBitmap(bmp.getWidth() + borderSize * 2, bmp.getHeight() + borderSize * 2, bmp.getConfig());
Canvas canvas = new Canvas(bmpWithBorder);
canvas.drawColor(Color.WHITE);
canvas.drawBitmap(bmp, borderSize, borderSize, null);
return bmpWithBorder;
}

remove those 2 lines from onItemClick
picker.setAdapter(adapter);
picker.scrollToPosition(position);
every time you setAdapter it resets position, and now you don't need to set a new position again.
this should work. If it doesn't, check this answer of mine (and their comments) about providing ID How to remain at a scroll position in RecyclerView after adding items at its first index and call notifydatasetchange

Add View overlay on top of ImageCardView

I am working on the TV app and trying to use leanback support library as much as possible. The issue I ran into is that I am trying to add a View on top of the ImageView in ImageCardView. I would like to have my custom View centered on top of that image.
I've tried simply adding the View on 0 index but it just pushes the image down and sits on top of it. I see the ImageCardView is FrameLayout but it seems that FrameLayout is changed so all the children are vertically aligned.
I've also tried to fetch a parent of ImageCardView, which is ShadowOverlayContainer, and add the View there but it still doesn't show.
Example for regular card:
What I am trying to accomplish:
Any suggestions how to add that View? Thank you.

I think this works.
onBindViewHolder(){
.
..
...
int count = ((ViewGroup)((ImageCardView) viewHolder.view).getMainImageView().getParent().getParent()).getChildCount();
((ViewGroup)((ImageCardView)
viewHolder.view).getMainImageView().getParent().getParent()).addView(xxx, count);
}

Since API Level 18 (JELLY_BEAN_MR2) you can use a ViewOverlay
https://developer.android.com/reference/android/view/ViewOverlay
https://developer.android.com/reference/android/view/View#getOverlay()
get a Drawable drawable = context.getDrawable(R.drawable.sample)
set its Bounds drawable.setBounds(0, 0, 50, 50)
add an Overlay view.getOverlay().add(drawable)
public class ImageCardViewPresenter extends Presenter {
#Override
public ViewHolder onCreateViewHolder(ViewGroup parent) {
ImageCardView imageCardView = new ImageCardView(parent.getContext());
imageCardView.setMainImageDimensions(100, 100);
return new ImageCardViewHolder(imageCardView);
}
#Override
public void onBindViewHolder(ViewHolder viewHolder, Object item) {
Model model = (Model) item;
ImageCardView imageCardView = (ImageCardView) viewHolder.view;
Context context = imageCardView.getContext();
imageCardView.setTitleText(model.getTitle());
imageCardView.setMainImage(context.getDrawable(model.getImageId());
Drawable badge = context.getDrawable(model.getBadgeId());
badge.setBounds(0, 0, 20, 20);
imageCardView.getOverlay().clear();
imageCardView.getOverlay().add(badge);
}
#Override
public void onUnbindViewHolder(ViewHolder viewHolder) {
ImageCardView imageCardView = (ImageCardView) viewHolder.view;
imageCardView.setMainImage(null);
imageCardView.getOverlay().clear();
}
public static class ImageCardViewHolder extends ViewHolder {
public ImageCardViewHolder(View view) {
super(view);
}
}
}
public class Model {
private String title;
#DrawableRes
private int imageId;
#DrawableRes
private int badgeId;
// getters and setters
}

How to zoom in/out item(only textview) of Vertical ScrollView in android when scroll Vertical

I want to create below layout under which item will scroll vertically. whenever we scroll up or down the centered(28) textview should be zoom in position.i found this link Gallery like view with center image zoom but they scroll horizontally using image based on their requirement. i need vertically scroll only using textview
please let me know if any body know the logic.......

First of all, thanks to #sanjay kumar had a good question.
After 2 days, I found a best solution for this question.
You can use RecyclerView and make sure the LinearLayoutManager should like this
LinearLayoutManager yourLinearLayout= new LinearLayoutManager(getApplicationContext());
yourLinearLayout.setOrientation(LinearLayoutManager.VERTICAL);
yourLinearLayout.setLayoutManager(yearLayoutManager);
The most difficult problem is how can you get the middle Item of recyclerView, well I think you can learn more in this link:
https://github.com/plattysoft/SnappingList
Finally, to make the middle Item bigger than the others. In the RecyclerView's Adapter should be like this
public class DateAdapter extends RecyclerView.Adapter<DateAdapter.DateViewHolder> {
private ArrayList<LabelerDate> dateDataList;
private static final int VIEW_TYPE_PADDING = 1;
private static final int VIEW_TYPE_ITEM = 2;
private int selectedItem = -1;
public DateAdapter(ArrayList<Datasource> data, int paddingWidthDate) {
this.dateDataList = data;
this.paddingWidthDate = paddingWidthDate;
}
#Override
public DateViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
//todo
}
#Override
public void onBindViewHolder(DateViewHolder holder, int position) {
Datasource data = dateDataList.get(position);
if (getItemViewType(position) == VIEW_TYPE_ITEM) {
holder.tvDate.setText(String.valueOf(data.valueDate));
holder.tvDate.setVisibility(View.VISIBLE);
holder.imgSmall.setVisibility(View.VISIBLE);
if (position == selectedItem) {
holder.tvDate.setTextColor(Color.parseColor("#094673"));
holder.tvDate.setTextSize(35);
holder.imgSmall.setBackgroundResource(R.color.textviewbold);
} else {
holder.tvDate.setTextColor(Color.GRAY);
holder.tvDate.setTextSize(35);
holder.imgSmall.setBackgroundResource(R.color.gray);
}
}
}
public void setSelecteditem(int selecteditem) {
this.selectedItem = selecteditem;
notifyDataSetChanged();
}
#Override
public int getItemViewType(int position) {
//todo
}
public class DateViewHolder extends RecyclerView.ViewHolder {
//todo
}}
After created The recyclerView, adapter and datasource. You can look at the onBindViewHolder(). If Item is selected then it's become bigger and change to black. If is not selected it will become Gray. My layout look like yours

use this library
Polidea view library
Put your TextView into a LinearLayout that lives on a ZoomView.
<ScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.polidea.ZoomView
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<LinearLayout
android:id="#+id/myLinearLayout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical" >
</LinearLayout>
</com.polidea.ZoomView>
</ScrollView>

The Polidea custom View didn't work in my case, as is. Had to a add a constructor with AttributeSet parameter, because it threw an xml inflation error. Also I had to make the ScrollView wrap only the TextView.

Hiding views in RecyclerView

I have code like this
public static class MyViewHolder extends RecyclerView.ViewHolder {
#InjectView(R.id.text)
TextView label;
public MyViewHolder(View itemView) {
super(itemView);
ButterKnife.inject(this, itemView);
}
public void hide(boolean hide) {
label.setVisibility(hide ? View.GONE : View.VISIBLE);
}
}
which maps to a single row in a RecyclerView. R.id.text is in fact the root view of the layout that gets inflated and passed in to the constructor here.
I'm using the default implementation of LinearLayoutManager.
In bindViewHolder, I call hide(true) on an instance of MyViewHolder, but instead of collapsing the row as expected, the row becomes invisible, maintaining its height and position in the RecyclerView. Has anyone else run into this issue?
How do you hide items in a RecyclerView?

There is no built in way to hide a child in RV but of course if its height becomes 0, it won't be visible :). I assume your root layout does have some min height (or exact height) that makes it still take space even though it is GONE.
Also, if you want to remove a view, remove it from the adapter, don't hide it. Is there a reason why you want to hide instead of remove ?

Put method setVisibility(boolean isVisible) in ViewHolder.
You can change itemView params(width and height) for LayoutManager:
public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
...
public void setVisibility(boolean isVisible){
RecyclerView.LayoutParams param = (RecyclerView.LayoutParams)itemView.getLayoutParams();
if (isVisible){
param.height = LinearLayout.LayoutParams.WRAP_CONTENT;
param.width = LinearLayout.LayoutParams.MATCH_PARENT;
itemView.setVisibility(View.VISIBLE);
}else{
itemView.setVisibility(View.GONE);
param.height = 0;
param.width = 0;
}
itemView.setLayoutParams(param);
}
public ViewHolder(View itemView) {
super(itemView);
...
}
}
and change visibility for ItemDecoration (Divider):
public class DividerItemDecoration extends RecyclerView.ItemDecoration {
...
#Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
...
for (int i = 0; i < parent.getChildCount(); i++) {
if (parent.getChildAt(i).getVisibility() == View.GONE)
continue;
/* draw dividers */
}
}
}

You CAN do it!
First, you need to detect which position of item that you want to hide. You can custom getItemViewType to do it.
Next, on onCreateViewHolder, depend on the view type. You can do something like this:
if(viewType == TYPE_HIDE) {
v = LayoutInflater.from(parent.getContext()).inflate(R.layout.empty_item, parent, false);
vHolder = new ViewHolder(context, v, viewType, this);
break;
}
return vHolder;
-> empty item is a layout that have nothing, (in other word, it is default layout whenever created). or code:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
</LinearLayout>
Hope it help!

Okay, so the way I did it in the end was I had my whole dataset, say, myObjects and I had scenarios where I would only want to show subsets of that dataset.
Since setting visibility of rows in RecyclerView doesn't cause the heights to collapse, and setting the heights of the rows did not appear to do anything either, what I had to do was just keep a secondary dataset called myObjectsShown which was nothing more than a List<Integer> that would index into myObjects to determine which objects would be displayed.
I would then intermittently update myObjectsShown to contain the correct indices.
Therefore,
public int getItemCount() {
return myObjectsShown.size();
}
and
public void onBindViewHolder(MyViewHolder holder, int position) {
Object myObject = myObjects.get(myObjectsShown.get(position));
// bind object to viewholder here...
}

For hiding view in RecyclerView I hide/show view in OnBindViewHolder:
if (item.isShown) {
vh.FooterLayout.setVisibility(View.Visible);
} else {
vh.FooterLayout.setVisibility(View.Gone);
}
And for example - from activity I simply redraw needed item:
_postListAdapter.notifyItemChanged(position)// if you want show/hide footer - position is amountOfPosts.size() and also change bool variable - amountOfPosts[amountOfPosts.size()].isShown

For the sake of completeness, you should note that setting view visibility to GONE would not hide the margins. You need to do something like this :
if(itemView.getVisibility() != GONE) itemView.setVisibility(GONE);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) itemView.getLayoutParams();
layoutParams.setMargins(0, 0, 0, 0);
itemView.setLayoutParams(layoutParams);

Scroll RecyclerView to show selected item on top

I'm looking for a way to scroll a RecyclerView to show the selected item on top.
In a ListView I was able to do that by using scrollTo(x,y) and getting the top of the element that need to be centered.
Something like:
#Override
public void onItemClick(View v, int pos){
mylistView.scrollTo(0, v.getTop());
}
The problem is that the RecyclerView returns an error when using it's scrollTo method saying
RecyclerView does not support scrolling to an absolute position
How can I scroll a RecyclerView to put the selected item at the top of the view?

If you are using the LinearLayoutManager or Staggered GridLayoutManager, they each have a scrollToPositionWithOffset method that takes both the position and also the offset of the start of the item from the start of the RecyclerView, which seems like it would accomplish what you need (setting the offset to 0 should align with the top).
For instance:
//Scroll item 2 to 20 pixels from the top
linearLayoutManager.scrollToPositionWithOffset(2, 20);

If you looking for vertical LinearLayout Manager you can achieve smooth scrolling using a custom LinearSmoothScroller:
import android.content.Context;
import android.graphics.PointF;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.LinearSmoothScroller;
import android.support.v7.widget.RecyclerView;
public class SnappingLinearLayoutManager extends LinearLayoutManager {
public SnappingLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
}
#Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
int position) {
RecyclerView.SmoothScroller smoothScroller = new TopSnappedSmoothScroller(recyclerView.getContext());
smoothScroller.setTargetPosition(position);
startSmoothScroll(smoothScroller);
}
private class TopSnappedSmoothScroller extends LinearSmoothScroller {
public TopSnappedSmoothScroller(Context context) {
super(context);
}
#Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return SnappingLinearLayoutManager.this
.computeScrollVectorForPosition(targetPosition);
}
#Override
protected int getVerticalSnapPreference() {
return SNAP_TO_START;
}
}
}
use an instance of the layoutmanager in recycle view and then calling recyclerView.smoothScrollToPosition(pos); will smooth scroll to selected position to top of the recycler view

//Scroll item pos
linearLayoutManager.scrollToPositionWithOffset(pos, 0);

You just need to call recyclerview.scrollToPosition(position). That's fine!
If you want to call it in adapter, just let your adapter has the instance of recyclerview or the activity or fragment which contains recyclerview,than implements the method getRecyclerview() in them.
I hope it can help you.

If you want to scroll automatic without show scroll motion then you need to write following code:
mRecyclerView.getLayoutManager().scrollToPosition(position);
If you want to display scroll motion then you need to add following code.
=>Step 1: You need to declare SmoothScroller.
RecyclerView.SmoothScroller smoothScroller = new
LinearSmoothScroller(this.getApplicationContext()) {
#Override
protected int getVerticalSnapPreference() {
return LinearSmoothScroller.SNAP_TO_START;
}
};
=>step 2: You need to add this code any event you want to perform scroll to specific position.
=>First you need to set target position to SmoothScroller.
smoothScroller.setTargetPosition(position);
=>Then you need to set SmoothScroller to LayoutManager.
mRecyclerView.getLayoutManager().startSmoothScroll(smoothScroller);

just call this method simply:
((LinearLayoutManager)recyclerView.getLayoutManager()).scrollToPositionWithOffset(yourItemPosition,0);
instead of:
recyclerView.scrollToPosition(yourItemPosition);

same with speed regulator
public class SmoothScrollLinearLayoutManager extends LinearLayoutManager {
private static final float MILLISECONDS_PER_INCH = 110f;
private Context mContext;
public SmoothScrollLinearLayoutManager(Context context,int orientation, boolean reverseLayout) {
super(context,orientation,reverseLayout);
mContext = context;
}
#Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
int position) {
RecyclerView.SmoothScroller smoothScroller = new TopSnappedSmoothScroller(recyclerView.getContext()){
//This controls the direction in which smoothScroll looks for your view
#Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return new PointF(0, 1);
}
//This returns the milliseconds it takes to scroll one pixel.
#Override
protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
return MILLISECONDS_PER_INCH / displayMetrics.densityDpi;
}
};
smoothScroller.setTargetPosition(position);
startSmoothScroll(smoothScroller);
}
private class TopSnappedSmoothScroller extends LinearSmoothScroller {
public TopSnappedSmoothScroller(Context context) {
super(context);
}
#Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return SmoothScrollLinearLayoutManager.this
.computeScrollVectorForPosition(targetPosition);
}
#Override
protected int getVerticalSnapPreference() {
return SNAP_TO_START;
}
}
}

Try what worked for me cool!
Create a variable private static int displayedposition = 0;
Now for the position of your RecyclerView in your Activity.
myRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
LinearLayoutManager llm = (LinearLayoutManager) myRecyclerView.getLayoutManager();
displayedposition = llm.findFirstVisibleItemPosition();
}
});
Place this statement where you want it to place the former site displayed in your view .
LinearLayoutManager llm = (LinearLayoutManager) mRecyclerView.getLayoutManager();
llm.scrollToPositionWithOffset(displayedposition , youList.size());
Well that's it , it worked fine for me \o/

what i did to restore the scroll position after refreshing the RecyclerView on button clicked:
if (linearLayoutManager != null) {
index = linearLayoutManager.findFirstVisibleItemPosition();
View v = linearLayoutManager.getChildAt(0);
top = (v == null) ? 0 : (v.getTop() - linearLayoutManager.getPaddingTop());
Log.d("TAG", "visible position " + " " + index);
}
else{
index = 0;
}
linearLayoutManager = new LinearLayoutManager(getApplicationContext());
linearLayoutManager.scrollToPositionWithOffset(index, top);
getting the offset of the first visible item from the top before creating the linearLayoutManager object and after instantiating it the scrollToPositionWithOffset of the LinearLayoutManager object was called.

I don't know why I didn't find the best answer but its really simple.
recyclerView.smoothScrollToPosition(position);
No errors
Creates Animations

What i may add here is how to make it work together with DiffUtil and ListAdapter
You may note that calling recyclerView.scrollToPosition(pos) or (recyclerView.layoutManager as LinearLayoutManager).scrollToPositionWithOffset(pos, offset) wouldn't work if called straight after adapter.submitList. It is because the differ looks for changes in a background thread and then asynchronously notifies adapter about changes. On a SO i have seen several wrong answers with unnecessary delays & etc to solve this.
To handle the situation properly the submitList has a callback which is invoked when changes have been applied.
So the proper kotlin implementations in this case are:
//memorise target item here and a scroll offset if needed
adapter.submitList(items) {
val pos = /* here you may find a new position of the item or just use just a static position. It depends on your case */
recyclerView.scrollToPosition(pos)
}
//or
adapter.submitList(items) { recyclerView.smoothScrollToPosition(pos) }
//or etc
adapter.submitList(items) { (recyclerView.layoutManager as LinearLayoutManager).scrollToPositionWithOffset(pos, offset) }

Introduction
None of the answers explain how to show last item(s) at the top. So, the answers work only for items that still have enough items above or below them to fill the remaining RecyclerView. For instance, if there are 59 elements and a 56-th element is selected it should be at the top as in the picture below:
So, let's see how to implement this in the next paragraph.
Solution
We could handle those cases by using linearLayoutManager.scrollToPositionWithOffset(pos, 0) and additional logic in the Adapter of RecyclerView - by adding a custom margin below the last item (if the last item is not visible then it means there's enough space fill the RecyclerView). The custom margin could be a difference between the root view height and the item height. So, your Adapter for RecyclerView would look as follows:
...
#Override
public void onBindViewHolder(ViewHolder holder, final int position) {
...
int bottomHeight = 0;
int itemHeight = holder.itemView.getMeasuredHeight();
// if it's the last item then add a bottom margin that is enough to bring it to the top
if (position == mDataSet.length - 1) {
bottomHeight = Math.max(0, mRootView.getMeasuredHeight() - itemHeight);
}
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)holder.itemView.getLayoutParams();
params.setMargins(0, 0, params.rightMargin, bottomHeight);
holder.itemView.setLayoutParams(params);
...
}
...

If your LayoutManager is LinearLayoutManager you can use scrollToPositionWithOffset(position,0); on it and it will make your item the first visible item in the list. Otherwise, you can use smoothScrollToPosition on the RecyclerView directly.
I ended up using the below code.
RecyclerView.LayoutManager layoutManager = mainList.getLayoutManager();
if (layoutManager instanceof LinearLayoutManager) {
// Scroll to item and make it the first visible item of the list.
((LinearLayoutManager) layoutManager).scrollToPositionWithOffset(position, 0);
} else {
mainList.smoothScrollToPosition(position);
}

scroll at particular position
and this helped me alot.
by click listener you can get the position in your adapter
layoutmanager.scrollToPosition(int position);

In my case my RecyclerView have a padding top like this
<android.support.v7.widget.RecyclerView
...
android:paddingTop="100dp"
android:clipToPadding="false"
/>
Then for scroll a item to top, I need to
recyclerViewLinearLayoutManager.scrollToPositionWithOffset(position, -yourRecyclerView.getPaddingTop());

please note that if scrollToPosition not work notice that your RecyclerView was inside a NestedScrollView; refer to this post

This is pretty simple
recyclerView.scrollToPosition(position)

If you've Recycler view inside nestedscrollview :
val y = recyclerview.getChildAt(0).y
recyclerview.smoothScrollTo(0, y.toInt())
If your Recycler view is not inside nestedscrollview :
recyclerview.smoothScrollToPosition(index)
or
recyclerview.layoutManager?.smoothScrollToPosition(recyclerview, null ,index)

I use the code below to smooth-scroll an item (thisView) to the top.
It works also for GridLayoutManager with views of different heights:
View firstView = mRecyclerView.getChildAt(0);
int toY = firstView.getTop();
int firstPosition = mRecyclerView.getChildAdapterPosition(firstView);
View thisView = mRecyclerView.getChildAt(thisPosition - firstPosition);
int fromY = thisView.getTop();
mRecyclerView.smoothScrollBy(0, fromY - toY);
Seems to work good enough for a quick solution.