RecyclerView里面的RecyclerView并不顺利

Question

There are some topics about RecyclerView inside RecyclerView but I see most of them do not fit my case. My case is I have a RecyclerView (verticle linear layout management) displays a list of CardView, each Cardview contains a inner RecyclerView (horizontal linear layout management). The problem is all about performance when scrolling, it is not smooth at all. I notice if I comment the setAdapter for the Inner Recyclerview, the scrooling become smooth, but I make the CardView not updated the new list. The code is something similar to this:

onBindViewHolder...{
    holder.innerRecycler.setAdapter(new InnerAdapter((data));
    // comment that line make the outer recyclerview smoothly but the CardView data not updated thanks to the view recycling.
}

I know a scrollable view inside a scrollable view is not a good idea but I dont see any other choices. Anyone face to this kind of layout before?. Thanks.

UPDATE (add more code).

// init outer recyclerview
mOuterRecyclerView = (RecyclerView) findViewById(...);
mOuterRecyclerView.setLayoutManagement(new LinearLayoutManagement(this));
mOuterRecyclerView.setHasFixedSize(true);
mOuterRecyclerView.setAdapter(new OuterAdapter(dataList));

// The adapter class for the outer one
onBindViewHolder(...){
    final dataItem = mItems.get(position);
    holder.innerRecycler.setAdapter(new InnerAdapter(dataItem.getList()));
}

// the holder for the outer
class MyHolder extends ViewHolder{
    RecyclerView innerRecycler;
    public MyHolder(View view){
        super(..);
        innerRecycler = findViewById(...);
    }
}
// the adapter for the inner
onBindViewHolder(...){
    final dataItem = mItems.get(pos);
    // async loading
    holder.tvTitle.setText(dataItem.getTitle);
}

The layout is pretty simple so I dont post the fully code here. :)

Answer 1

@Paul i had the same requirement and the below trick worked. Put the parent recyclerview inside NestedScrollView and in your onCreate method, set.

mRecyclerView.setHasFixedSize(true);
mRecyclerView.setNestedScrollingEnabled(false);

This prevents scroll of parent recyclerview and scroll becomes absolutely smooth.

Answer 2

There is no issue in such an approach as long as they scroll along different axes.You could enable RecyclerView.startNestedScroll(int) and also handle situations like overscroll.This delay would be because you are reinitiating an adpater everytime. You could try something different like maintaining a map of adpaters and calling RecyclerView.swapAdapter(args...) in bindVH.

Another good step could also be using a common pool for recycled views using RecyclerView.setRecycledViewPool(args...) . I have created and used a list of 100+ plus items with a nested (different axis) recycler and have not faced issues .

If you would provide more code( where you have written async loading ) I could help you more.But I suggest you go through the API and the design patterns and that should solve your issue.

Answer 3

Since there are some user ask me how to archive, I'm going to post what I do. The sugession that @Droidekas seems a good point but I dont follow that.

What I did is:

1. Each horizontal recycler view is a item of a vertical recycler view

2. When I need to set the data for the particular vertical item (onBindViewHolder), I use the horizontal recycler adapter setNotifyDataSetChanged instead of setting a completely new adapter or swapping it. This way, I got the vertical recyler run very smoothly.

The vertical recyler adapter structure could be:

Vertical Item view holder  -> Vertical Item[Name, List<Horizontal item>,...]
Vertical Item view holder  -> Vertical Item[Name, List<Horizontal item>,...]

In OnBindViewHolder

holder.setData(VerticalItem)

In the Holder, I have a setData method looks like:

setData(VerticalItem item){
    mItems = item.getHorizontalItems();
    mHorizontalAdapter.notifyDataSetChanged();
}

Hope it helps. :D