RecyclerView - How to smooth scroll to top of item on a certain position

Question

On a RecyclerView  I am able to suddenly scroll to the top of a selected item by using     LinearLayoutManager  recyclerView getLayoutManager    scrollToPositionWithOffset position  0     However  this abruptly moves the item to the top position  I want to move to the top of an item smoothly   I ve also tried   recyclerView smoothScrollToPosition position     but it does not work well as it does not move the item to the position selected to the top  It merely scrolls the list until the item on the position is visible

User · Accepted Answer

RecyclerView is designed to be extensible  so there is no need to subclass the LayoutManager  as droidev suggested  just to perform the scrolling   Instead  just create a SmoothScroller with the preference SNAP TO START   RecyclerView SmoothScroller smoothScroller   new LinearSmoothScroller context       Override protected int getVerticalSnapPreference         return LinearSmoothScroller SNAP TO START           Now you set the position where you want to scroll to   smoothScroller setTargetPosition position     and pass that SmoothScroller to the LayoutManager   layoutManager startSmoothScroll smoothScroller

User · Answer

The easiest way I ve found to scroll a RecyclerView is as follows      Define the Index we wish to scroll to  final int lIndex   0     Assign the RecyclerView s LayoutManager  this getRecyclerView   setLayoutManager this getLinearLayoutManager        Scroll the RecyclerView to the Index  this getLinearLayoutManager   smoothScrollToPosition this getRecyclerView    new RecyclerView State    lIndex

User · Answer

Probably  droidev approach is the correct one  but I just want to publish something a little bit different  which does basically the same job and doesn t require extension of the LayoutManager   A NOTE here - this is gonna work well if your item  the one that you want to scroll on the top of the list  is visible on the screen and you just want to scroll it to the top automatically  It is useful when the last item in your list has some action  which adds new items in the same list and you want to focus the user on the new added items   int recyclerViewTop   recyclerView getTop    int positionTop   recyclerView findViewHolderForAdapterPosition positionToScroll     null   recyclerView findViewHolderForAdapterPosition positionToScroll  itemView getTop     200  final int calcOffset   positionTop - recyclerViewTop     then the actual scroll is gonna happen with  x offset   0  and  y offset   calcOffset  recyclerView scrollBy 0  offset     The idea is simple  1  We need to get the top coordinate of the recyclerview element  2  We need to get the top coordinate of the view item that we want to scroll to the top  3  At the end with the calculated offset we need to do   recyclerView scrollBy 0  offset     200 is just example hard coded integer value that you can use if the viewholder item doesn t exist  because that is possible as well

User · Answer

I want to more fully address the issue of scroll duration  which  should you choose any earlier answer  will in fact will vary dramatically  and unacceptably  according to the amount of scrolling necessary to reach the target position from the current position     To obtain a uniform scroll duration the velocity  pixels per millisecond  must account for the size of each individual item - and when the items are of non-standard dimension then a whole new level of complexity is added     This may be why the RecyclerView developers deployed the too-hard basket for this vital aspect of smooth scrolling     Assuming that you want a semi-uniform scroll duration  and that your list contains semi-uniform items then you will need something like this        Smoothly scroll to specified position allowing for interval specification   lt br gt     Note crude deceleration towards end of scroll     param rv        Your RecyclerView     param toPos     Position to scroll to     param duration  Approximate desired duration of scroll  ms      throws IllegalArgumentException    private static void smoothScroll RecyclerView rv  int toPos  int duration  throws IllegalArgumentException       int TARGET SEEK SCROLL DISTANCE PX   10000         See androidx recyclerview widget LinearSmoothScroller     int itemHeight   rv getChildAt 0  getHeight        Height of first visible view  NB  ViewGroup method      itemHeight   itemHeight   33                       Example pixel Adjustment for decoration      int fvPos     LinearLayoutManager rv getLayoutManager    findFirstCompletelyVisibleItemPosition        int i   Math abs  fvPos - toPos    itemHeight       if  i    0    i    int  Math abs rv getChildAt 0  getY           final int totalPix   i                             Best guess  Total number of pixels to scroll     RecyclerView SmoothScroller smoothScroller   new LinearSmoothScroller rv getContext               Override protected int getVerticalSnapPreference                 return LinearSmoothScroller SNAP TO START                     Override protected int calculateTimeForScrolling int dx                int ms    int    duration   dx    float totalPix                   Now double the interval for the last fling              if  dx  lt  TARGET SEEK SCROLL DISTANCE PX     ms   ms 2       Crude deceleration                lg format  For dx  d we allot  dms   dx  ms                return ms                         lg format  Total pixels from    d to  d    d   itemHeight  dpix     fvPos  toPos  totalPix  itemHeight        smoothScroller setTargetPosition toPos       rv getLayoutManager   startSmoothScroll smoothScroller       PS  I curse the day I began indiscriminately converting ListView to RecyclerView

User · Answer

This is an extension function I wrote in Kotlin to use with the RecyclerView  based on  Paul Woitaschek answer    fun RecyclerView smoothSnapToPosition position  Int  snapMode  Int   LinearSmoothScroller SNAP TO START      val smoothScroller   object   LinearSmoothScroller this context        override fun getVerticalSnapPreference    Int   snapMode     override fun getHorizontalSnapPreference    Int   snapMode       smoothScroller targetPosition   position   layoutManager  startSmoothScroll smoothScroller      Use it like this   myRecyclerView smoothSnapToPosition itemPosition

User · Answer

i Used Like This    recyclerView getLayoutManager   smoothScrollToPosition recyclerView  new RecyclerView State    5

User · Answer

Override the calculateDyToMakeVisible calculateDxToMakeVisible function in LinearSmoothScroller to implement the offset Y X position   override fun calculateDyToMakeVisible view  View  snapPreference  Int   Int       return super calculateDyToMakeVisible view  snapPreference  - ConvertUtils dp2px 10f

User · Answer

I have create an extension method based on position of items in a list which is bind with recycler view Smooth scroll in large list takes longer time to scroll   use this to improve speed of scrolling and also have the smooth scroll animation  Cheers   fun RecyclerView  perfectScroll size  Int up Boolean   true  smooth  Boolean   true    this  apply       if  size  gt  0            if  smooth                val minDirectScroll   10    left item to scroll               smooth scroll             if  size  gt  minDirectScroll                      scroll directly to certain position                 val newSize   if  up  minDirectScroll else size - minDirectScroll                   scroll to new position                 val newPos   newSize  - 1                   direct scroll                 scrollToPosition newPos                    smooth scroll to rest                 perfectScroll minDirectScroll  true                 else                     direct smooth scroll                 smoothScrollToPosition if  up  0 else size-1                          else                 direct scroll             scrollToPosition if  up  0 else size-1                       Just call the method anywhere using rvList perfectScroll list size up true smooth true

User · Answer

for this you have to create a custom LayoutManager  public class LinearLayoutManagerWithSmoothScroller extends LinearLayoutManager        public LinearLayoutManagerWithSmoothScroller Context context            super context  VERTICAL  false              public LinearLayoutManagerWithSmoothScroller 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 LinearLayoutManagerWithSmoothScroller this                      computeScrollVectorForPosition targetPosition                       Override         protected int getVerticalSnapPreference                 return SNAP TO START                      use this for your RecyclerView and call smoothScrollToPosition   example     recyclerView setLayoutManager new LinearLayoutManagerWithSmoothScroller context     recyclerView smoothScrollToPosition position     this will scroll to top of the RecyclerView item of specified position   hope this helps

User · Answer

Extend  LinearLayout  class and override the necessary functions Create an instance of the above class in your fragment or activity  Call  recyclerView smoothScrollToPosition targetPosition    CustomLinearLayout kt    class CustomLayoutManager private val context  Context  layoutDirection  Int     LinearLayoutManager context  layoutDirection  false         companion object            This determines how smooth the scrolling will be       private       const val MILLISECONDS PER INCH   300f            override fun smoothScrollToPosition recyclerView  RecyclerView  state  RecyclerView State  position  Int           val smoothScroller  LinearSmoothScroller   object  LinearSmoothScroller context             fun dp2px dpValue  Float   Int             val scale   context resources displayMetrics density           return  dpValue   scale   0 5f  toInt                         change this and the return super type to  calculateDyToMakeVisible  if the layout direction is set to VERTICAL         override fun calculateDxToMakeVisible view  View     snapPreference   Int   Int             return super calculateDxToMakeVisible view  SNAP TO END  - dp2px 50f                       This controls the direction in which smoothScroll looks for your view         override fun computeScrollVectorForPosition targetPosition  Int   PointF               return this  CustomLayoutManager computeScrollVectorForPosition targetPosition                       This returns the milliseconds it takes to scroll one pixel          override fun calculateSpeedPerPixel displayMetrics  DisplayMetrics   Float             return MILLISECONDS PER INCH   displayMetrics densityDpi                         smoothScroller targetPosition   position       startSmoothScroll smoothScroller              Note  The above example is set to HORIZONTAL direction  you can pass VERTICAL HORIZONTAL during initialization    If you set the direction to VERTICAL you should change the  calculateDxToMakeVisible  to  calculateDyToMakeVisible   also mind the supertype call return value   Activity Fragment kt        smoothScrollerLayoutManager   CustomLayoutManager context  LinearLayoutManager HORIZONTAL  recyclerView layoutManager   smoothScrollerLayoutManager       fun onClick          targetPosition passed from the adapter to activity fragment   recyclerView smoothScrollToPosition targetPosition

User · Answer

We can try like this      recyclerView getLayoutManager   smoothScrollToPosition recyclerView new RecyclerView State    recyclerView getAdapter   getItemCount

User · Answer

Thanks   droidev for the solution  If anyone looking for Kotlin solution  refer this       class LinearLayoutManagerWithSmoothScroller  LinearLayoutManager       constructor context  Context    this context  VERTICAL false      constructor context  Context  orientation  Int  reverseValue  Boolean    super context  orientation  reverseValue       override fun smoothScrollToPosition recyclerView  RecyclerView   state  RecyclerView State   position  Int            super smoothScrollToPosition recyclerView  state  position          val smoothScroller   TopSnappedSmoothScroller recyclerView  context          smoothScroller targetPosition   position         startSmoothScroll smoothScroller             private class TopSnappedSmoothScroller context  Context     LinearSmoothScroller context           var mContext   context         override fun computeScrollVectorForPosition targetPosition  Int   PointF                return LinearLayoutManagerWithSmoothScroller mContext as Context                       computeScrollVectorForPosition targetPosition                     override fun getVerticalSnapPreference    Int               return SNAP TO START

User · Answer

You can reverse your list by list reverse   and finaly call RecylerView scrollToPosition 0      list reverse       layout   LinearLayoutManager this LinearLayoutManager VERTICAL true        RecylerView scrollToPosition 0

[android] RecyclerView - How to smooth scroll to top of item on a certain position?

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