How to find out that RecyclerView has finished update?

Question

I use SortedList in RecyclerView Adapter and I'd like to know when RecyclerView has finished its update after I change data in Adapter (and called proper method e.g. notifyItemRangeChanged). Is there any way to do this?

My problem is that I need to scroll RecyclerView to the top after filtering its content. I call from Activity method on my Adapter which filter items on its member. After that I just call scrollToPosition(0) on RecyclerView and its not always work as expected, especially when after changes operation on list is only 1 item.

Here is code of update method I call on my adapter:

private SortedList<Game> games;
private ArrayList<Game> allGames;

public void search(String query) {
    replaceAll(filterGames(query));
}

public void replaceAll(Collection<Game> games) {
    this.games.beginBatchedUpdates();
    List<Game> gamesToRemove = new ArrayList<>();
    for (int i = 0; i < this.games.size(); i++) {
        Game game = this.games.get(i);
        if (!games.contains(game)) {
            gamesToRemove.add(game);
        }
    }
    for (Game game : gamesToRemove) {
        this.games.remove(game);
    }
    this.games.addAll(games);
    this.games.endBatchedUpdates();
}

private Collection<Game> filterGames(String query) {
    query = query.toLowerCase();
    List<Game> filteredGames = new ArrayList<>();
    for (Game game : allGames) {
        String gameTitle = game.getTitle().toLowerCase();
        if (gameTitle.contains(query)) {
            filteredGames.add(game);
        }
    }
    return filteredGames;
}

And here how I call it from Activity:

private RecyclerView gamesList;
private GameAdapter gamesAdapter;

@Override
public boolean onQueryTextChange(String newText) {
    gamesAdapter.search(newText);
    gamesList.scrollToPosition(0);
    return false;
}

I want to scroll RecyclerView to the top after add/remove items. When I try to scroll just after I start update on adapter there are problems because items are still being processed. — ostojan, Apr 12 '17 at 19:34
`because items are still being processed` how can they "be processed" if they are out of the screen, thus they are detached from window? — azizbekian, Apr 12 '17 at 19:36
They are moving from old to new positions. I'm talking about animations. When I've added delay between call for update and scroll to first position there was no problem. — ostojan, Apr 12 '17 at 19:37
I think you are missing something. Most possibly you won't ever need to know when "update" has finished. If you wait until "update" finishes (which means that e.g. 7 times `onBindViewHolder` was called, because that much items are active currently), then how would it affect the item that is off the screen? You still will be performing that "processing" as soon as `onBindViewHolder()` would be called for that item. — azizbekian, Apr 12 '17 at 19:40
Well I understand what you're saying, but its simple not working form me. Maybe I explain myself better in question description. — ostojan, Apr 12 '17 at 19:55

Mortada · Answer 1 · 2017-04-12T19:54:40.350

0

you can use RecyclerAdapter.registerAdapterDataObserver(RecyclerView.AdapterDataObserver observer)

For listening to changed views:

extends LayoutManager then override onItemUpdated(RecyclerView recyclerView, int positionStart, int itemCount, Object payload)

edited Apr 12 '17 at 19:54

answered Apr 12 '17 at 19:10

Mortada

189
2
10

I've tired this but in that way I can only find out that update was requested, not that has finished. – ostojan Apr 12 '17 at 19:14
it seems like you need to use LayoutManager.onItemUpdated – Mortada Apr 12 '17 at 19:52
It's almost what I want. It work properly if I remove items from list. When I add items before actual first item and call scrollToPosition(0) in onItemUpdated it doesn't work. – ostojan Apr 12 '17 at 20:11
use postDelayed() for scrolling – Mortada Apr 12 '17 at 20:30
2

I know that postDelayed works, but I'm looking for "cleaner" solution. – ostojan Apr 12 '17 at 20:34

score 0 · Answer 2 · answered Apr 12 '17 at 19:17

0

Try using,

recyclerView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
                @Override
                public void onGlobalLayout() {
                    //At this point the layout is complete and the 
                    //dimensions of recyclerView and any child views are known.
                }
            });

answered Apr 12 '17 at 19:17

Shivam

702
2
10
25

1

It's still not what I'm looking for. This method looks like being called each app frame. And even if i set flag that I've edited data and only then perform my actions changes in RecyclerView are still being proceed. – ostojan Apr 12 '17 at 19:36

score 0 · Answer 3 · edited Jun 16 '20 at 15:24

0

You can use recyclerView.itemAnimator?.isRunning for this purpose.

edited Jun 16 '20 at 15:24

desertnaut

57,590
26
140
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answered Jun 16 '20 at 14:15

Guilherme Santos

328
4
11

score 0 · Answer 4 · answered Oct 14 '20 at 11:08

Your issue seams related to this.

I tried this and it worked for me. Here is the Kotlin extension

fun RecyclerView.runWhenReady(action: () -> Unit) {
    val globalLayoutListener = object: ViewTreeObserver.OnGlobalLayoutListener {
        override fun onGlobalLayout() {
            action()
            viewTreeObserver.removeOnGlobalLayoutListener(this)
        }
    }
    viewTreeObserver.addOnGlobalLayoutListener(globalLayoutListener)
}

then call it

myRecyclerView.runWhenReady {
    // Your action
}

How to find out that RecyclerView has finished update?

4 Answers4