How to add a custom adapter to an AutoCompleteTextView

Here Code is working for me,

Set This adapter to autocompletetextview

AutoCompleteTextView etProductSearch = (AutoCompleteTextView)getView().findViewById(R.id.edtSearchBoxTakeOrder);
ProductSearchAdapter adapter = new ProductSearchAdapter(getActivity(), android.R.layout.simple_dropdown_item_1line, productList);
etProductSearch.setAdapter(adapter );

ProductSearchAdapter class

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Filter;
import android.widget.TextView;

public class ProductSearchAdapter extends ArrayAdapter<ProductDataModel> {
    private ArrayList<ProductDataModel> items;
    private ArrayList<ProductDataModel> itemsAll;
    private ArrayList<ProductDataModel> suggestions;
    private int viewResourceId;

    @SuppressWarnings("unchecked")
    public ProductSearchAdapter(Context context, int viewResourceId,
            ArrayList<ProductDataModel> items) {
        super(context, viewResourceId, items);
        this.items = items;
        this.itemsAll = (ArrayList<ProductDataModel>) items.clone();
        this.suggestions = new ArrayList<ProductDataModel>();
        this.viewResourceId = viewResourceId;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        if (v == null) {
            LayoutInflater vi = (LayoutInflater) getContext().getSystemService(
                    Context.LAYOUT_INFLATER_SERVICE);
            v = vi.inflate(viewResourceId, null);
        }
        ProductDataModel product = items.get(position);
        if (product != null) {
              TextView productLabel = (TextView)  v.findViewById(android.R.id.text1);
            if (productLabel != null) {
                productLabel.setText(product.getProductName());
            }
        }
        return v;
    }

    @Override
    public Filter getFilter() {
        return nameFilter;
    }

    Filter nameFilter = new Filter() {
        public String convertResultToString(Object resultValue) {
            String str = ((ProductDataModel) (resultValue)).getProductName();
            return str;
        }

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            if (constraint != null) {
                suggestions.clear();
                for (ProductDataModel product : itemsAll) {
                    if (product.getProductName().toLowerCase()
                            .startsWith(constraint.toString().toLowerCase())) {
                        suggestions.add(product);
                    }
                }
                FilterResults filterResults = new FilterResults();
                filterResults.values = suggestions;
                filterResults.count = suggestions.size();
                return filterResults;
            } else {
                return new FilterResults();
            }
        }

        @Override
        protected void publishResults(CharSequence constraint,
                FilterResults results) {
            @SuppressWarnings("unchecked")
            ArrayList<ProductDataModel> filteredList = (ArrayList<ProductDataModel>) results.values;
            if (results != null && results.count > 0) {
                clear();
                for (ProductDataModel c : filteredList) {
                    add(c);
                }
                notifyDataSetChanged();
            }
        }
    };

}

According to the documentation, the inferred type of setAdapter in AutoCompleteTextView is :

<T extends ListAdapter & Filterable> void setAdapter(T adapter)

Your adapter must be a ListAdapter (which BaseAdapter is, so far so good) and a Filterable, which BaseAdapter is not, nor is your Adapter implementation. I would extend an ArrayAdapter, which is Filterable, not to mention is would simplify your implementation (some of your methods duplicate methods of ArrayAdapter for the same result) :

public class TwoLineDropdownAdapter extends ArrayAdapter<TwoLineDropDown> {

    private LayoutInflater mInflater = null;
    private Activity activity;

    public TwoLineDropdownAdapter(Activity a, ArrayList<TwoLineDropDown> items) {
        super(a, 0, items);
        activity = a;
        mInflater = (LayoutInflater) activity
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    public static class ViewHolder {

        public TextView title;
        public TextView description;
    }

    public View getView(final int position, View convertView, ViewGroup parent) {

        ViewHolder holder;

        if (convertView == null) {

            holder = new ViewHolder();

            convertView = mInflater.inflate(R.layout.dropdown_text_twoline,
                    parent, false);
            holder.title = (TextView) convertView
                    .findViewById(R.id.text1);
            holder.description = (TextView) convertView
                    .findViewById(R.id.text2);

            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        return convertView;
    }
}