RecyclerView onBindViewHolder only called when getItemViewType changes

Question

I have a viewholder with multiple viewtypes.

When scrolling onBindViewHolder is only called when getItemViewType changes value. This causes my list items to not be updated properly.

Is this a bug? Or I'm i doing something wrong here. This seems very strange behaviour from the new recyclerView class.

Here is my adapter:

package se.davison.smartrecycleradapter;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.util.SparseIntArray;
import android.view.LayoutInflater;
import android.view.ViewGroup;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;

/**
 * Created by richard on 10/11/14.
 */
public class SectionAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {


    private static final String TAG = SectionAdapter.class.getSimpleName();
    private final LayoutInflater inflater;
    private final int sectionLayoutId;
    private SparseIntArray positionSection;
    private LinkedHashMap<AdapterItem, List<AdapterItem>> items = new LinkedHashMap<AdapterItem, List<AdapterItem>>();
    private List<Class<? extends AdapterItem>> itemTypes = new ArrayList<Class<? extends AdapterItem>>(20);

    public SectionAdapter(Context context, int sectionLayoutId, LinkedHashMap<AdapterItem, List<AdapterItem>> items) {
        this.inflater = LayoutInflater.from(context);
        this.sectionLayoutId = sectionLayoutId;
        this.items = items;
        initList(items);
    }

    public SectionAdapter(Context context, int sectionLayoutId) {
        this.inflater = LayoutInflater.from(context);
        this.sectionLayoutId = sectionLayoutId;
        this.items = new LinkedHashMap<AdapterItem, List<AdapterItem>>();
        initList(items);
    }


    @Override
    public int getItemViewType(int position) {
        AdapterItem item = getItem(position);
        Log.d(TAG, position + ": class " + item.getClass());
        return itemTypes.indexOf(item.getClass());
    }

    @Override
    public int getItemCount() {
        int count = 0;
        if (items == null) {
            return 0;
        }

        for (AdapterItem key : items.keySet()) {
            count++;
            List<AdapterItem> childItems = items.get(key);
            if (childItems != null) {
                count += childItems.size();
            }
        }
        return count;
    }

    private void initList(HashMap<AdapterItem, List<AdapterItem>> items) {
        positionSection = new SparseIntArray(items.size());
        int count = 0;
        int sectionIndex = -1;
        for (AdapterItem key : items.keySet()) {
            Class headerClass = key.getClass();
            if (!itemTypes.contains(headerClass)) {
                itemTypes.add(headerClass);
            }
            List<AdapterItem> childItems = items.get(key);
            sectionIndex = count;
            if (childItems != null) {
                for (AdapterItem item : childItems) {
                    Class clazz = item.getClass();
                    if (!itemTypes.contains(clazz)) {
                        itemTypes.add(clazz);
                    }
                    positionSection.put(count, sectionIndex);
                    count++;
                }

            }
            count++;
        }
        setHasStableIds(true);
    }

    private AdapterItem getItem(int position) {

        int totalChildCount = 0;
        int separatorCount = 0;
        for (AdapterItem key : items.keySet()) {
            if (position == 0 || position == totalChildCount + separatorCount) {
                return key;
            }
            separatorCount++;
            List<AdapterItem> list = items.get(key);
            int couldCount = countList(list);
            if (position < totalChildCount + separatorCount + couldCount) {
                return list.get(position - (totalChildCount + separatorCount));
            }

            totalChildCount += couldCount;
        }

        return null;
    }

    public void setItems(LinkedHashMap<AdapterItem, List<AdapterItem>> items) {
        this.items = items;
        notifyDataSetChanged();
    }

    public void setItemsAtHeader(int id, List<AdapterItem> items) {
        AdapterItem header = null;
        for (AdapterItem key : this.items.keySet()) {
            if (key.headerId() == id) {
                header = key;
                break;
            }
        }
        if (header == null) {
            throw new IllegalArgumentException(String.format("No header with id %s is found", id));
        }
        setItemsAtHeader(header, items);
    }

    private void setItemsAtHeader(AdapterItem header, List<AdapterItem> items) {
        this.items.put(header, items);
    }

    private int countList(List<?> list) {
        return list == null ? 0 : list.size();
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
        AdapterItem firstItem = getFirstItemWithClass(itemTypes.get(viewType));
        return firstItem.onCreateViewHolder(inflater, viewGroup);
    }

    private AdapterItem getFirstItemWithClass(Class<? extends AdapterItem> clazz) {

        for (AdapterItem key : items.keySet()) {
            if (key.getClass() == clazz) {
                return key;
            }
            List<AdapterItem> childItems = items.get(key);
            if (childItems != null) {
                for (AdapterItem item : childItems) {
                    if (item.getClass() == clazz) {
                        return item;
                    }
                }
            }
        }
        throw new IllegalStateException("Something is wrong, you dont have any items with that class in your list");
    }


    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
        AdapterItem item = getItem(position);
        Log.d(TAG, "ITEM = " + item.getClass().getSimpleName());
        Log.d(TAG, "POS = " + position);
        if (item instanceof OneLineAdapterItem) {
            Log.d(TAG, "TEXT = " + ((OneLineAdapterItem) item).getText());
        }

        item.onBindViewHolder(viewHolder, position);
    }
}

I've also abstracted out the items like so:

public abstract class AdapterItem<VH extends RecyclerView.ViewHolder> {


    public boolean isHeader(){
        return false;
    }

    public int headerId(){
        return -1;
    }

    public abstract VH onCreateViewHolder(LayoutInflater inflater, ViewGroup parent);

    public abstract void onBindViewHolder(VH viewHolder, int position);
}

And for sections

public class SectionAdapterItem extends AdapterItem<SectionAdapterItem.ViewHolder> {

    private String text;
    private boolean dividerVisible = false;

    public static class ViewHolder extends RecyclerView.ViewHolder{

        TextView titel;
        ImageView divider;

        public ViewHolder(View itemView) {
            super(itemView);
            titel = (TextView) itemView.findViewById(android.R.id.title);
            divider = (ImageView) itemView.findViewById(android.R.id.icon);
        }
    }

    public void setDividerVisible(boolean dividerVisible) {
        this.dividerVisible = dividerVisible;
    }

    public boolean isDividerVisible() {
        return dividerVisible;
    }

    @Override
    public boolean isHeader() {
        return true;
    }

    @Override
    public int headerId() {
        return super.headerId();
    }

    public SectionAdapterItem(String text) {
        this.text = text;
    }

    @Override
    public ViewHolder onCreateViewHolder(LayoutInflater inflater, ViewGroup parent) {
        return new ViewHolder(inflater.inflate(R.layout.top_header, parent, false));
    }

    @Override
    public void onBindViewHolder(ViewHolder viewHolder, int position) {
        viewHolder.titel.setText(text);
        viewHolder.divider.setVisibility(dividerVisible?View.VISIBLE:View.GONE);
    }
}

It works fine for the frist visible rows, but then it fails.

what do you mean by onBind is never called? What happens instead, it does not show anything? Scrolling stops ? — yigit, Nov 13 '14 at 20:06
@yigit the first items are showen properly. But when i start scrolling my items are just recycled so their data is not updated since onBind doesn't get called for each row as I scroll. I'll add a few screenshots soon! — Richard, Nov 14 '14 at 08:04
for me, this was the problem. http://stackoverflow.com/a/29162119/371749 — cV2, Mar 20 '15 at 10:39

score 39 · Accepted Answer · answered Nov 29 '14 at 10:54

39

I've forgot to implement getItemId when using setHasStableIds(true);

Implementing that solved the issue!

answered Nov 29 '14 at 10:54

Richard

13,521
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Was facing same issue. Saved my day. Tons of thanks..:) – Dory May 29 '15 at 12:33
1

Worked for me for multiple view types. I wonder why it is not working without stable ids. Does it mean 'multiple view types in adapter' implies 'stabled ids' ? – Vadim Kotov Jul 20 '15 at 14:58
1

I met the same problem, even I set has stable ID true and correctly implement the getItemID method. However, it just reduce the frequency of the problem. Some of my item views are still not updated when I scroll the grid. Any idea? – Robin Aug 05 '15 at 09:48
Hi, can you put some code?, I don't know where put getItemId, thanks. – Oct 13 '15 at 10:34
@delive in your adapter override getItemId and then call myAdapter.setHasStableIds(true) from your activity or fragment or similar – Richard Oct 13 '15 at 15:09
getItemID, what value ? Long ? I pass objectsCustoms always, I onlye see post that says ... call setHasStableIds in the constructor (adapter) – Oct 14 '15 at 15:32
This helped me to solve the issue that was persisting for several month! – Sevastyan Savanyuk Apr 07 '17 at 12:22

score 7 · Answer 2 · answered Jan 14 '16 at 06:27

When you set setHasStableIds(true) means that if we request an ID for a location, any specific item will always return the same ID regardless of its position within the list. This enables us to identify a specific item even if its position changes, which will be useful later on.

For that you need to implememt getItemId method in adapter and just return it's positions.

@Override
    public long getItemId(int position) {
        return position;
    }

RecyclerView onBindViewHolder only called when getItemViewType changes

2 Answers2

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