Search adapter - 'java.lang.Object[] java.util.Collection.toArray()' on a null object reference

Question

I made a SearchAdapter that filters items in realtime, but there is NPE and I have no clue what to do... It works sometimes but gives NPE and shutdowns the application.

These are the links that I have followed to make this adapter - https://codinginflow.com/tutorials/android/searchview-recyclerview https://www.youtube.com/watch?v=ujKDN_ZtGHQ

And Here are adapter codes and error logs.

public class SearchAdapter extends RecyclerView.Adapter<SearchAdapter.SearchViewHolder> implements Filterable {

private ArrayList<SearchItem> searchList;
private ArrayList<SearchItem> searchListFull;
private SelectedPlace selectedPlace;

class SearchViewHolder extends RecyclerView.ViewHolder {
    ImageView imageView;
    TextView searchPlace;
    TextView searchFolder;
    SearchViewHolder(View itemView) {
        super(itemView);
        imageView = itemView.findViewById(R.id.image_view);
        searchPlace = itemView.findViewById(R.id.text_view1);
        searchFolder = itemView.findViewById(R.id.text_view2);

        itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                selectedPlace.selectedPlace(searchList.get(getAdapterPosition()));
            }
        });
    }
}
SearchAdapter(ArrayList<SearchItem> searchList, SelectedPlace selectedPlace) {
    this.searchList = searchList;
    searchListFull = new ArrayList<>(searchList);
    this.selectedPlace = selectedPlace;
}
@NonNull
@Override
public SearchAdapter.SearchViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.search_item,
            parent, false);
    return new SearchViewHolder(v);
}
@Override
public void onBindViewHolder(@NonNull SearchAdapter.SearchViewHolder holder, int position) {
    SearchItem currentItem = searchList.get(position);
    if(currentItem.getAttempts() < 3){
        holder.imageView.setImageResource(R.drawable.ps_place_under);
    } else if(currentItem.getStarred() == 0){
        holder.imageView.setImageResource(R.drawable.ps_place_over);
    } else {
        holder.imageView.setImageResource(R.drawable.ic_star_chk_24dp);
    }
    holder.searchPlace.setText(currentItem.getPlace());
    holder.searchFolder.setText(currentItem.getFolder());
}
@Override
public int getItemCount() {
    return searchList.size();
}

public interface SelectedPlace{
    void selectedPlace(SearchItem searchItem);
}

@Override
public Filter getFilter() {
    return searchFilter;
}
private Filter searchFilter = new Filter() {
    @Override
    protected FilterResults performFiltering(CharSequence constraint) {
        List<SearchItem> filteredList = new ArrayList<>();
        if (constraint == null || constraint.length() == 0) {
            filteredList.addAll(searchListFull);
        } else {
            String filterPattern = constraint.toString().toLowerCase().trim();
            for (SearchItem item : searchListFull) {
                if (item.getFolder().toLowerCase().contains(filterPattern)) {
                    filteredList.add(item);
                }
                else if (item.getPlace().toLowerCase().contains(filterPattern)){
                    filteredList.add(item);
                }
            }
        }
        FilterResults results = new FilterResults();
        results.values = filteredList;
        return results;
    }
    @Override
    protected void publishResults(CharSequence constraint, FilterResults results) {
        searchList.clear();
        searchList.addAll((List) results.values);
        notifyDataSetChanged();
    }
};

}

ERROR LOG ----------------------------------------------------------------------------

java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object[] 

java.util.Collection.toArray()' on a null object reference      
at java.util.ArrayList.addAll(ArrayList.java:588)
        at com.ljh.GetOut.SearchAdapter$1.publishResults(SearchAdapter.java:104)
        at android.widget.Filter$ResultsHandler.handleMessage(Filter.java:284)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

Answer 1

Your results.values might be null, or it may contain other objects instead of SearchItem's. You should be a little more cautious to prevent this kind of errors.

Try something like this:

@Override
protected void publishResults(CharSequence constraint, FilterResults results) 
{
    searchList.clear();
    if(results.values instanceof List){
        for(Object item : (List<Object>)results.values){
            if(item instanceof SearchItem){
                searchList.add((SearchItem) item);
            }
        }
    }
    notifyDataSetChanged();
}