对https://github.com/google-developer-training/android-fundamentals/tree/master/WordListSql%20finished中WordListAdapter.java的优化，用于学习systrace的用法

WordListAdapterAsync.java

/*
 * Copyright (C) 2016 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.example.wordlistsql;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import java.util.List;

/**
 * Implements a simple Adapter for a RecyclerView.
 * Demonstrates how to add a click handler for each item in the ViewHolder.
 */
public class WordListAdapterAsync extends RecyclerView.Adapter<WordListAdapterAsync.WordViewHolder> {

    /**
     *  Custom view holder with a text view and two buttons.
     */
    class WordViewHolder extends RecyclerView.ViewHolder {
        public final TextView wordItemView;
        Button delete_button;
        Button edit_button;

        public WordViewHolder(View itemView) {
            super(itemView);
            wordItemView = (TextView) itemView.findViewById(R.id.word);
            delete_button = (Button)itemView.findViewById(R.id.delete_button);
            edit_button = (Button)itemView.findViewById(R.id.edit_button);
        }
    }

    private static final String TAG = WordListAdapterAsync.class.getSimpleName();

    public static final String EXTRA_ID = "ID";
    public static final String EXTRA_WORD = "WORD";
    public static final String EXTRA_POSITION = "POSITION";

    private final LayoutInflater mInflater;
//    WordListOpenHelper mDB;
    Context mContext;
    List<WordItem> mList;

    public WordListAdapterAsync(Context context, List<WordItem> list) {
        mInflater = LayoutInflater.from(context);
        mContext = context;
        mList = list;
    }

    @Override
    public WordViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = mInflater.inflate(R.layout.wordlist_item, parent, false);
        return new WordViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(WordViewHolder holder, int position) {
        WordItem current = mList.get(position);
        holder.wordItemView.setText(current.getWord());
        // Keep a reference to the view holder for the click listener
        final WordViewHolder h = holder; // needs to be final for use in callback
        // Attach a click listener to the DELETE button.
        holder.delete_button.setOnClickListener(new MyButtonOnClickListener(
                current.getId(), null)  {


            @Override
            public void onClick(View v ) {
                // You have to get the position like this, you can't hold a reference
                Log.d (TAG + "onClick", "VHPos " + h.getAdapterPosition() + " ID " + id);
                int deleted = -1; //mDB.delete(id);
                if (deleted >= 0)
                    notifyItemRemoved(h.getAdapterPosition());
            }
        });

        // Attach a click listener to the EDIT button.
        holder.edit_button.setOnClickListener(new MyButtonOnClickListener(
                current.getId(), current.getWord()) {

            @Override
            public void onClick(View v) {
                Intent intent = new Intent(mContext, EditWordActivity.class);

                intent.putExtra(EXTRA_ID, id);
                intent.putExtra(EXTRA_POSITION, h.getAdapterPosition());
                intent.putExtra(EXTRA_WORD, word);

                // Start an empty edit activity.
                ((Activity) mContext).startActivityForResult(intent, MainActivity.WORD_EDIT);
            }
        });
    }

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