RecyclerView store / restore state between activities

Solution 1:

Ok, so to answer my own question. As I understand it, since they've decoupled the layout code and the view recycling code (thus the name), the component responsible one for holding layout state (and restoring it) is now the LayoutManager used in your recyclerview.

Thus, to store state you use same pattern, but on the layout manager and not the recyclerview:

protected void onSaveInstanceState(Bundle state) {
     super.onSaveInstanceState(state);

     // Save list state
     mListState = mLayoutManager.onSaveInstanceState();
     state.putParcelable(LIST_STATE_KEY, mListState);
}

Restore state in the onRestoreInstanceState():

protected void onRestoreInstanceState(Bundle state) {
    super.onRestoreInstanceState(state);

    // Retrieve list state and list/item positions
    if(state != null)
        mListState = state.getParcelable(LIST_STATE_KEY);
}

Then update the LayoutManager (I do in onResume()):

@Override
protected void onResume() {
    super.onResume();

    if (mListState != null) {
        mLayoutManager.onRestoreInstanceState(mListState);
    }
}

Solution 2:

I found a better solution - this solution has the following benefits :

1. RecyclerView state is saved and restored on rotation of phone
2. RecyclerView state is saved and restored on returning to activity with RecyclerView (which wasn't destroyed whilst the other activity was showing - which means that onRestoreInstanceState() isn't called !!)

CODE

public class ActivityItemList extends AppCompatActivity
{
    private final String KEY_RECYCLER_STATE = "recycler_state";
    private RecyclerView mRecyclerView;
    private static Bundle mBundleRecyclerViewState;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list);//set to whatever layout name you have

        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);//set to whatever view id you use
        // don't forget to set your adapter
    }

    @Override
    protected void onPause()
    {
        super.onPause();

        // save RecyclerView state
        mBundleRecyclerViewState = new Bundle();
        Parcelable listState = mRecyclerView.getLayoutManager().onSaveInstanceState();
        mBundleRecyclerViewState.putParcelable(KEY_RECYCLER_STATE, listState);
    }

    @Override
    protected void onResume()
    {
        super.onResume();

        // restore RecyclerView state
        if (mBundleRecyclerViewState != null) {
            Parcelable listState = mBundleRecyclerViewState.getParcelable(KEY_RECYCLER_STATE);
            mRecyclerView.getLayoutManager().onRestoreInstanceState(listState);
        }
    }
}

Solution 3:

Use this code in onPause() and onResume() to save and restore scroll position-

private Parcelable recyclerViewState;
recyclerViewState = mrecyclerView.getLayoutManager().onSaveInstanceState();//save
mrecyclerView.getLayoutManager().onRestoreInstanceState(recyclerViewState);//restore

Solution 4:

That's my solution, it restores both items and RecyclerView position

1) save recycler view state in onSaveInstanceState method

@Override
protected void onSaveInstanceState(Bundle outState) {
    Parcelable listState = myRecyclerView.getLayoutManager().onSaveInstanceState();
    // putting recyclerview position
    outState.putParcelable(SAVED_RECYCLER_VIEW_STATUS_ID, listState);
    // putting recyclerview items
    outState.putParcelableArrayList(SAVED_RECYCLER_VIEW_DATASET_ID,mDataset);
    super.onSaveInstanceState(outState);
}

2) Check savedInstanceState Bundle in onCreate method

@Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (savedInstanceState==null){
            getRemoteData(); // No saved data, get data from remote
        }else{
            restorePreviousState(); // Restore data found in the Bundle
        }
    }

3) Restore recycler view data if the screen has been rotated

public void restorePreviousState(){
    // getting recyclerview position
    mListState = mSavedInstanceState.getParcelable(SAVED_RECYCLER_VIEW_STATUS_ID);
    // getting recyclerview items
    mDataset = mSavedInstanceState.getParcelableArrayList(SAVED_RECYCLER_VIEW_DATASET_ID);
    // Restoring adapter items
    mAdapter.setItems(mDataset);
    // Restoring recycler view position
    mRvMedia.getLayoutManager().onRestoreInstanceState(mListState);
}