JSONArray cannot be cast to java.util.ArrayList

Question

I am writing ad Adapter class with a Filter and I get this error in publishResults method. The list is loaded, when I type something in filter, it starts filtering, but when deleting chars and reaching 0 length, the app crash with this error, moreover some of imageView (CardView type) are inverted, so maybe I'm doing something wrong in parsing too.

Fragment

public class ColorViewFragment extends Fragment {

    private RecyclerView recyclerView;
    private JSONArray json;
    private ColorListAdapter adapter;

    private EditText editColor;

    @Nullable @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.color_list, container, false);
        this.recyclerView = view.findViewById(R.id.recyclerView);

        /*
        try {
            this.recyclerView.setAdapter(new ColorListAdapter(this.json));
        } catch (JSONException e) {
            e.printStackTrace();
        }
        */

        try {
            adapter = new ColorListAdapter(json);
        } catch (JSONException e) {
            e.printStackTrace();
        }
        recyclerView.setAdapter(adapter);


        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity());
        this.recyclerView.setLayoutManager(layoutManager);

        //
        editColor = view.findViewById(R.id.editText);
        editColor.addTextChangedListener(new TextWatcher() {

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {

                ColorViewFragment.this.adapter.getFilter().filter(s);

            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });

        return view;
    }

    public void setJSON(JSONArray newJson){
        this.json = newJson;
    }


}

Adapter

public class ColorListAdapter extends RecyclerView.Adapter implements Filterable {

    private JSONArray colorList;

    private List<String> colorListFiltered = new ArrayList<String>();

    public ColorListAdapter(JSONArray json) throws JSONException {
        super();
        if (json != null) {
            this.colorList = json;

                for (int i=0;i<json.length();i++){
                    //colorListFiltered.add((colorList.getString(i)));
                    colorListFiltered.add(json.getJSONObject(i).getString("Name"));
                }
        }
    }


    @Override
    public Filter getFilter() {
        return new colorFilter();
    }


    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.fragment_color_view, viewGroup, false);
        return new ColorListHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder viewHolder, int i) {
        try {
            ((ColorListHolder) viewHolder).setContentValue(i);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    @Override
    public int getItemCount() {
        return this.colorListFiltered.size();
    }

    private class ColorListHolder extends RecyclerView.ViewHolder {

        private TextView colorCodeText;
        private TextView colorNameText;
        private CardView imageView;

        public ColorListHolder(@NonNull View itemView) {
            super(itemView);
            this.colorCodeText = itemView.findViewById(R.id.colorCode_text);
            this.colorNameText = itemView.findViewById(R.id.colorName_text);
            this.imageView = itemView.findViewById(R.id.colorView);
        }

        public void setContentValue(int index) throws JSONException {

            this.colorNameText.setText(colorListFiltered.get(index));
            //this.colorNameText.setText(((JSONObject) colorList.get(index)).getString("Name"));
            this.colorCodeText.setText(((JSONObject) colorList.get(index)).getString("ColorCode"));
            this.imageView.setCardBackgroundColor(Color.parseColor(((JSONObject) colorList.get(index)).getString("HexString")));

        }
    }


    public class colorFilter extends Filter{

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {

            FilterResults Result = new FilterResults();
            // if constraint is empty return the original names
            if(constraint.length() == 0 ){
                Result.values = colorList;
                Result.count = colorList.length();
                return Result;
            }
            else {

                List<String> Filtered_Names = new ArrayList<String>();
                String filterString = constraint.toString().toLowerCase();
                String filterableString = "";

                for (int i = 0; i < colorList.length(); i++) {
                    try {
                        filterableString = (colorList.getJSONObject(i)).getString("Name");
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                    if (filterableString.toLowerCase().contains(filterString)) {
                        Filtered_Names.add(filterableString);
                    }
                }

                Result.values = Filtered_Names;
                Result.count = Filtered_Names.size();
                return Result;

            }

        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {

            colorListFiltered = (ArrayList<String>) results.values;
            notifyDataSetChanged();
        }
    }


}

Answer 1

The problem occurs in your performFiltering(CharSequence constraint) when you return a JSONArray object instead a ArrayList in the first if statement

To fix it do this changes:

 public class colorFilter extends Filter{

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {

            FilterResults Result = new FilterResults();
            // if constraint is empty return the original names
            if(constraint.length() == 0 ) {
                ArrayList<String> arrColorList = new ArrayList<>();
                for (int i = 0; i < colorList.length(); i++) {                                                      
                    arrColorList.add(colorList.getJSONObject(i).getString("Name"));
                }
                Result.values = arrColorList;
                Result.count = arrColorList.size();
                return Result;
            }
            else {

                List<String> Filtered_Names = new ArrayList<String>();
                String filterString = constraint.toString().toLowerCase();
                String filterableString = "";

                for (int i = 0; i < colorList.length(); i++) {
                    try {
                        filterableString = (colorList.getJSONObject(i)).getString("Name");
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                    if (filterableString.toLowerCase().contains(filterString)) {
                        Filtered_Names.add(filterableString);
                    }
                }

                Result.values = Filtered_Names;
                Result.count = Filtered_Names.size();
                return Result;

            }

        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {

            colorListFiltered = (ArrayList<String>) results.values;
            notifyDataSetChanged();
        }
    }