How to save RecyclerView s scroll position using RecyclerView State

Question

I have a question about Android s RecyclerView State   I am using a RecyclerView  how could I use and bind it with RecyclerView State   My purpose is to save the RecyclerView s scroll position

User · Answer

Beginning from version 1 2 0-alpha02 of androidx recyclerView library  it is now automatically managed  Just add it with   implementation  androidx recyclerview recyclerview 1 2 0-alpha02    And use   adapter stateRestorationPolicy   StateRestorationPolicy PREVENT WHEN EMPTY   The StateRestorationPolicy enum has 3 options    ALLOW     the default state  that restores the RecyclerView state immediately  in the next layout pass PREVENT WHEN EMPTY     restores the RecyclerView state only when the adapter is not empty  adapter getItemCount     0   If your data is loaded async  the RecyclerView waits until data is loaded and only then the state is restored  If you have default items  like headers or load progress indicators as part of your Adapter  then you should use the PREVENT option  unless the default items are added using MergeAdapter  MergeAdapter waits for all of its adapters to be ready and only then it restores the state  PREVENT     all state restoration is deferred until you set ALLOW or PREVENT WHEN EMPTY    Note that at the time of this answer  recyclerView library is still in alpha03  but alpha phase is not suitable for production purposes

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Update  Starting from recyclerview 1 2 0-alpha02 release StateRestorationPolicy has been introduced  It could be a better approach to the given problem   This topic has been covered on android developers medium article   Also   rub  n-viguera shared more details in the answer below  https   stackoverflow com a 61609823 892500  Old answer  If you are using LinearLayoutManager  it comes with pre-built save api linearLayoutManagerInstance onSaveInstanceState   and restore api linearLayoutManagerInstance onRestoreInstanceState       With that  you can save the returned parcelable to your outState  e g    outState putParcelable  KeyForLayoutManagerState   linearLayoutManagerInstance onSaveInstanceState         and restore restore position with the state you saved  e g   Parcelable state   savedInstanceState getParcelable  KeyForLayoutManagerState    linearLayoutManagerInstance onRestoreInstanceState state     To wrap all up  your final code will look something like  private static final String BUNDLE RECYCLER LAYOUT    classname recycler layout           This is a method for Fragment      You can do the same in onCreate or onRestoreInstanceState      Override public void onViewStateRestored  Nullable Bundle savedInstanceState        super onViewStateRestored savedInstanceState        if savedInstanceState    null                Parcelable savedRecyclerLayoutState   savedInstanceState getParcelable BUNDLE RECYCLER LAYOUT           recyclerView getLayoutManager   onRestoreInstanceState savedRecyclerLayoutState             Override public void onSaveInstanceState Bundle outState        super onSaveInstanceState outState       outState putParcelable BUNDLE RECYCLER LAYOUT  recyclerView getLayoutManager   onSaveInstanceState         Edit  You can also use the same apis with the GridLayoutManager  as it is a subclass of LinearLayoutManager  Thanks  wegsehen for the suggestion   Edit  Remember  if you are also loading data in a background thread  you will need to a call to onRestoreInstanceState within your onPostExecute onLoadFinished method for the position to be restored upon orientation change  e g    Override protected void onPostExecute ArrayList lt Movie gt  movies        mLoadingIndicator setVisibility View INVISIBLE       if  movies    null            showMoviePosterDataView            mDataAdapter setMovies movies         mRecyclerView getLayoutManager   onRestoreInstanceState mSavedRecyclerLayoutState             else               showErrorMessage

User · Answer

Store  lastFirstVisiblePosition     LinearLayoutManager rv getLayoutManager    findFirstCompletelyVisibleItemPosition      Restore    LinearLayoutManager  rv getLayoutManager    scrollToPosition lastFirstVisiblePosition     and if that doesn t work  try     LinearLayoutManager  rv getLayoutManager    scrollToPositionWithOffset lastFirstVisiblePosition 0    Put store in onPause   and restore in onResume

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I ve had the same requirement  but the solutions here didn t quite get me across the line  due to the source of data for the recyclerView   I was extracting the RecyclerViews  LinearLayoutManager state in onPause    private Parcelable state   Public void onPause         state   mLinearLayoutManager onSaveInstanceState        Parcelable state is saved in onSaveInstanceState Bundle outState   and extracted again in onCreate Bundle savedInstanceState   when savedInstanceState    null   However  the recyclerView adapter is populated and updated by a ViewModel LiveData object returned by a DAO call to a Room database   mViewModel getAllDataToDisplay mSelectedData  observe this  new Observer lt List lt String gt  gt           Override     public void onChanged  Nullable final List lt String gt  displayStrings            mAdapter swapData displayStrings           mLinearLayoutManager onRestoreInstanceState state               I eventually found that restoring the instance state directly after the data is set in the adapter would keep the scroll-state across rotations   I suspect this either is because the LinearLayoutManager state that I d restored was being overwritten when the data was returned by the database call  or the restored state was meaningless against an  empty  LinearLayoutManager   If the adapter data is available directly  ie not contigent on a database call   then restoring the instance state on the LinearLayoutManager can be done after the adapter is set on the recyclerView   The distinction between the two scenarios held me up for ages

User · Answer

All layout managers bundled in the support library already know how to save and restore scroll position  Scroll position is restored on the first layout pass which happens when the following conditions are met   a layout manager is attached to the RecyclerView an adapter is attached to the RecyclerView  Typically you set the layout manager in XML so all you have to do now is  Load the adapter with data Then attach the adapter to the RecyclerView  You can do this at any time  it s not constrained to Fragment onCreateView or Activity onCreate  Example  Ensure the adapter is attached every time the data is updated  viewModel liveData observe this           Load adapter      adapter data   it      if  list adapter    adapter               Only set the adapter if we didn t do it already          list adapter   adapter           The saved scroll position is calculated from the following data   Adapter position of the first item on the screen Pixel offset of the top of the item from the top of the list  for vertical layout   Therefore you can expect a slight mismatch e g  if your items have different dimensions in portrait and landscape orientation   The RecyclerView ScrollView whatever needs to have an android id for its state to be saved

User · Answer

Activity java   public RecyclerView LayoutManager mLayoutManager   Parcelable state       mLayoutManager   new LinearLayoutManager this        Inside  onCreate    lifecycle method  put the below code        if state    null        mLayoutManager onRestoreInstanceState state                 Override     protected void onResume             super onResume             if  state    null                mLayoutManager onRestoreInstanceState state                           Override     protected void onPause             super onPause             state   mLayoutManager onSaveInstanceState                Why I m using OnSaveInstanceState   in onPause   means  While switch to another activity onPause would be called It will save that scroll position and restore the position when we coming back from another activity

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For me  the problem was that I set up a new layoutmanager every time I changed my adapter  loosing que scroll position on recyclerView

User · Answer

On Android API Level 28  I simply ensure that I set up my LinearLayoutManager and RecyclerView Adapter in my Fragment onCreateView method  and everything Just Worked      I didn t need to do any onSaveInstanceState or onRestoreInstanceState work   Eugen Pechanec s answer explains why this works

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In my case I was setting the RecyclerView s layoutManager both in XML and in onViewCreated  Removing the assignment in onViewCreated fixed it   with  binding list        layoutManager    LinearLayoutManager context      adapter   MyAdapter   apply           listViewModel data observe viewLifecycleOwner              Observer                   it  let   setItems it

User · Answer

You can either use adapter stateRestorationPolicy   StateRestorationPolicy PREVENT WHEN EMPTY which is introduced in recyclerview 1 2 0-alpha02 https   medium com androiddevelopers restore-recyclerview-scroll-position-a8fbdc9a9334 but it has some issues such as not working with inner RecyclerView  and some other issues you can check out in medium post s comment section  Or you can use ViewModel with SavedStateHandle which works for inner RecyclerViews  screen rotation and process death  Create a ViewModel with saveStateHandle val scrollState      savedStateHandle getLiveData lt Parcelable  gt  KEY LAYOUT MANAGER STATE   use Parcelable scrollState to save and restore state as answered in other posts or by adding a scroll listener to RecyclerView and recyclerView addOnScrollListener object   RecyclerView OnScrollListener              override fun onScrollStateChanged recyclerView  RecyclerView  newState  Int                super onScrollStateChanged recyclerView  newState              if  newState    RecyclerView SCROLL STATE IDLE                   scrollState value   mLayoutManager onSaveInstanceState

User · Answer

I would just like to share the recent predicament I encounter with the RecyclerView  I hope that anyone experiencing the same problem will benefit   My Project Requirement  So I have a RecyclerView that list some clickable items in my Main Activity  Activity-A   When the Item is clicked a new Activity is shown with the Item Details  Activity-B    I implemented in the Manifest file the that the Activity-A is the parent of Activity-B  that way  I have a back or home button on the ActionBar of the Activity-B  Problem  Every time I pressed the Back or Home button in the Activity-B ActionBar  the Activity-A goes into the full Activity Life Cycle starting from onCreate    Even though I implemented an onSaveInstanceState   saving the List of the RecyclerView s Adapter  when Activity-A starts it s lifecycle  the saveInstanceState is always null in the onCreate   method   Further digging in the internet  I came across the same problem but the person noticed that the Back or Home button below the Anroid device  Default Back Home button   the Activity-A does not goes into the Activity Life-Cycle   Solution    I removed the  Tag for Parent Activity in the manifest for Activity-B I enabled the home or back button on Activity-B  Under onCreate   method add this line supportActionBar  setDisplayHomeAsUpEnabled true  In the overide fun onOptionsItemSelected   method  I checked for the item ItemId   on which item is clicked based on the id  The Id for the back button is   android R id home  Then implement a finish   function call inside the android R id home  This will end the Activity-B and bring Acitivy-A without going through the entire life-cycle    For my requirement this is the best solution so far        override fun onCreate savedInstanceState  Bundle         super onCreate savedInstanceState      setContentView R layout activity show project       supportActionBar  title   projectName     supportActionBar  setDisplayHomeAsUpEnabled true        override fun onOptionsItemSelected item  MenuItem    Boolean        when item  itemId            android R id home - gt                finish                        return super onOptionsItemSelected item

User · Answer

You don t have to save and restore the state by yourself anymore  If you set unique ID in xml and recyclerView setSaveEnabled true   true by default  system will automatically do it  Here is more about this  http   trickyandroid com saving-android-view-state-correctly

User · Answer

This is how I restore RecyclerView position with GridLayoutManager after rotation when you need to reload data from internet with AsyncTaskLoader   Make a global variable of Parcelable and GridLayoutManager and a static final string   private Parcelable savedRecyclerLayoutState  private GridLayoutManager mGridLayoutManager  private static final String BUNDLE RECYCLER LAYOUT    recycler layout     Save state of gridLayoutManager in onSaveInstance      Override         protected void onSaveInstanceState Bundle outState                super onSaveInstanceState outState               outState putParcelable BUNDLE RECYCLER LAYOUT               mGridLayoutManager onSaveInstanceState                 Restore in onRestoreInstanceState   Override     protected void onRestoreInstanceState Bundle savedInstanceState            super onRestoreInstanceState savedInstanceState              restore recycler view at same position         if  savedInstanceState    null                savedRecyclerLayoutState   savedInstanceState getParcelable BUNDLE RECYCLER LAYOUT                     Then when loader fetches data from internet you restore recyclerview position in onLoadFinished    if savedRecyclerLayoutState  null                   mGridLayoutManager onRestoreInstanceState savedRecyclerLayoutState                     of course you have to instantiate gridLayoutManager inside onCreate  Cheers

User · Answer

I wanted to save Recycler View s scroll position when navigating away from my list activity and then clicking the back button to navigate back  Many of the solutions provided for this problem were either much more complicated than needed or didn t work for my configuration  so I thought I d share my solution   First save your instance state in onPause as many have shown  I think it s worth emphasizing here that this version of onSaveInstanceState is a method from the RecyclerView LayoutManager class   private LinearLayoutManager mLayoutManager  Parcelable state            Override         public void onPause                 super onPause                state   mLayoutManager onSaveInstanceState                The key to getting this to work properly is to make sure you call onRestoreInstanceState after you attach your adapter  as some have indicated in other threads  However the actual method call is much simpler than many have indicated   private void someMethod         mVenueRecyclerView setAdapter mVenueAdapter       mLayoutManager onRestoreInstanceState state

User · Answer

I had the same problem with a minor difference  I was using Databinding  and I was setting recyclerView adapter and the layoutManager in the binding methods   The problem was that data-binding was happening after onResume so it was resetting my layoutManager after onResume and that means it was scrolling back to original place every time  So when I stopped setting layoutManager in Databinding adaptor methods  it works fine again

User · Answer

How do you plan to save last saved position with RecyclerView State   You can always rely on ol  good save state  Extend RecyclerView and override onSaveInstanceState   and onRestoreInstanceState          Override     protected Parcelable onSaveInstanceState             Parcelable superState   super onSaveInstanceState            LayoutManager layoutManager   getLayoutManager            if layoutManager    null  amp  amp  layoutManager instanceof LinearLayoutManager               mScrollPosition     LinearLayoutManager  layoutManager  findFirstVisibleItemPosition                      SavedState newState   new SavedState superState           newState mScrollPosition   mScrollPosition          return newState              Override     protected void onRestoreInstanceState Parcelable state            super onRestoreInstanceState state           if state    null  amp  amp  state instanceof SavedState               mScrollPosition     SavedState  state  mScrollPosition              LayoutManager layoutManager   getLayoutManager                if layoutManager    null                 int count   layoutManager getItemCount                  if mScrollPosition    RecyclerView NO POSITION  amp  amp  mScrollPosition  lt  count                     layoutManager scrollToPosition mScrollPosition                                                      static class SavedState extends android view View BaseSavedState           public int mScrollPosition          SavedState Parcel in                super in               mScrollPosition   in readInt                      SavedState Parcelable superState                super superState                       Override         public void writeToParcel Parcel dest  int flags                super writeToParcel dest  flags               dest writeInt mScrollPosition                     public static final Parcelable Creator lt SavedState gt  CREATOR                   new Parcelable Creator lt SavedState gt                   Override             public SavedState createFromParcel Parcel in                    return new SavedState in                               Override             public SavedState   newArray int size                    return new SavedState size

User · Answer

I Set variables in onCreate    save scroll position in onPause   and set scroll position in onResume    public static int index   -1  public static int top   -1  LinearLayoutManager mLayoutManager    Override public void onCreate Bundle savedInstanceState          Set Variables     super onCreate savedInstanceState       cRecyclerView     RecyclerView  findViewById R id conv recycler       mLayoutManager   new LinearLayoutManager this       cRecyclerView setHasFixedSize true       cRecyclerView setLayoutManager mLayoutManager        Override public void onPause         super onPause          read current recyclerview position     index   mLayoutManager findFirstVisibleItemPosition        View v   cRecyclerView getChildAt 0       top    v    null    0    v getTop   - cRecyclerView getPaddingTop         Override public void onResume         super onResume          set recyclerview position     if index    -1                mLayoutManager scrollToPositionWithOffset  index  top

User · Answer

Here is my Approach to save them and maintain the state of recyclerview in a fragment  First  add config changes in your parent activity as below code   android configChanges  orientation screenSize    Then in your Fragment declare these instance method s  private  Bundle mBundleRecyclerViewState  private Parcelable mListState   null  private LinearLayoutManager mLinearLayoutManager    Add below code in your  onPause method   Override public void onPause         super onPause          This used to store the state of recycler view     mBundleRecyclerViewState   new Bundle        mListState  mTrailersRecyclerView getLayoutManager   onSaveInstanceState        mBundleRecyclerViewState putParcelable getResources   getString R string recycler scroll position key   mListState       Add onConfigartionChanged Method like below    Override public void onConfigurationChanged Configuration newConfig        super onConfigurationChanged newConfig         When orientation is changed then grid column count is also changed so get every time     Log e TAG   onConfigurationChanged           if  mBundleRecyclerViewState    null            new Handler   postDelayed new Runnable                   Override             public void run                     mListState   mBundleRecyclerViewState getParcelable getResources   getString R string recycler scroll position key                    mTrailersRecyclerView getLayoutManager   onRestoreInstanceState mListState                             50             mTrailersRecyclerView setLayoutManager mLinearLayoutManager       This approch will reslove your problem  if You have diffrent layout manager then just replace upper layout manager

[android] How to save RecyclerView's scroll position using RecyclerView.State?

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