为什么在自定义AutocompleteTextview适配器中调用performFiltering（）两次

Question

我创建了一个自定义AutoCompleteTextView适配器。第一次调用performFiltering（）时，它会过滤结果并返回FilterResults的实例（具有正确的值）。之后系统调用PublishResults（）方法，该方法调用notifyDataSetChanged（）。

在调用notifyDataSetChanged（）之后，立即再次调用performFiltering方法。返回结果后，它不再调用PublishResults（）。

我还应该注意，过滤后的结果不会传递给AutoComplete小部件。相反，整个原始数据集显示在下拉列表中。并且值得注意的是，即使我将窗口小部件上的阈值设置为2，也会在输入第一个字符后调用performFiltering（）。

所以我的问题是：（1）为什么在notifyDataSetChanged（）之后第二次调用performFiltering（）？，（2）为什么在满足阈值之前调用performFiltering（）？，以及（3）最常见的是什么筛选结果的原因没有进入下拉列表？

import android.content.Context;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.view.LayoutInflater;
import android.widget.BaseAdapter;
import android.widget.Filterable;
import android.widget.Filter;
import android.widget.TextView;

import java.util.ArrayList;

/**
 * Created by John on 12/31/2016.
 */

public class myContactsAutoCompleteAdapter extends BaseAdapter
                                            implements Filterable {

    Context context;
    private LayoutInflater inflator;
    private ArrayList<Contacts.ContactDataRow> contactsList;
    private ArrayList<Contacts.ContactDataRow> suggestions = new ArrayList<>();

    public myContactsAutoCompleteAdapter(Context ctx, ArrayList<Contacts.ContactDataRow> data ) {
        this.context = ctx;
        this.contactsList = data;
        this.inflator = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    @Override
    public int getCount() {
        return contactsList.size();
    }

    @Override
    public Object getItem(int position) {
        return contactsList.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        if (convertView == null) {
            convertView = inflator.inflate(R.layout.contacts_listview_item, null);
            viewHolder = new ViewHolder();
            viewHolder.txt_name = (TextView) convertView.findViewById(R.id.txt_contact_name);
            viewHolder.txt_phone = (TextView) convertView.findViewById(R.id.txt_contact_phone);
            viewHolder.txt_phonetype = (TextView) convertView.findViewById(R.id.txt_contact_type);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        viewHolder.txt_name.setText(contactsList.get(position).displayName);
        viewHolder.txt_phone.setText(contactsList.get(position).phone);
        viewHolder.txt_phonetype.setText(contactsList.get(position).phoneType);

        return convertView;
    }

    private static class ViewHolder {
        TextView txt_name;
        TextView txt_phone;
        TextView txt_phonetype;
    }

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

    private class ContactsAutocompleteFilter extends Filter {

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {

            FilterResults filterResults = new FilterResults();

            if (constraint != null && constraint.length() >= 2) {
                suggestions.clear();

                //Check for similarities in data from constraint
                for (Contacts.ContactDataRow row : contactsList) {
                    if (row.displayName.toLowerCase().contains(constraint.toString().toLowerCase())) {
                        suggestions.add(row);
                    }
                }

                filterResults.values = suggestions;
                filterResults.count = suggestions.size();
            }

            return filterResults;

        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            if (results != null && results.count > 0) {
                notifyDataSetChanged();
            } else {
                notifyDataSetInvalidated();
            }
        }
    }
}

编辑：我更新了这个以包含整个适配器类