本篇是对上一篇对RecyclerView.Adapter做一个简单的封装内容的补充 ，如果没有看过上一篇文章，请先阅读上一篇文章。

在上一篇文章的末尾提到，BaseRecyclerAdapter虽然能够简化部分功能的代码量，但是对于为itemView的每一个控件绑定监听器这一功能是没有做到简化的，本篇的内容就是解决这个问题。

先贴出没有封装的适配器代码

public class RecordAdapter extends RecyclerView.Adapter<RecordAdapter.RecordHolder> {

    private OnItemClickListener onItemClickListener;

    //上下文环境
    private Context context;
    //数据集合
    private List<Record> data;

    public RecordAdapter(Context context, List<Record> data) {
        this.context = context;
        this.data = data;
    }

    /**
     * 刷新数据
     * @param data
     */
    public void refresh(List<Record> data){
        this.data = data;
        notifyDataSetChanged();
    }

    @Override
    public RecordHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.item_record, parent, false);
        return new RecordHolder(view);
    }

    @Override
    public void onBindViewHolder(RecordHolder holder, int position) {
        Record record = data.get(position);
        holder.bind(record);
    }


    @Override
    public int getItemCount() {
        return data == null ? 0 : data.size();
    }

    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

    class RecordHolder extends RecyclerView.ViewHolder {

        //数据
        private Record record;

        TextView tvId;
        TextView tvRemark;
        TextView tvCreatedAt;

        public RecordHolder(View itemView) {
            super(itemView);
            tvId = (TextView) itemView.findViewById(R.id.tvId);
            tvRemark = (TextView) itemView.findViewById(R.id.tvRemark);
            tvCreatedAt = (TextView) itemView.findViewById(R.id.tvCreatedAt);
            bindListener();
        }

        //绑定数据
        public void bind(Record record) {
            this.record = record;
            tvId.setText(record.getId().toString());
            tvRemark.setText(record.getRemark());
            tvCreatedAt.setText(record.getCreatedAt().toString());
        }

        /**
         * 绑定监听器
         */
        private void bindListener() {
            tvId.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (onItemClickListener != null) {
                        onItemClickListener.onIdClick(v, record);
                    }
                }
            });

            tvRemark.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (onItemClickListener != null) {
                        onItemClickListener.onRemarkClick(v, record);
                    }
                }
            });

            tvCreatedAt.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (onItemClickListener != null) {
                        onItemClickListener.onCreationTimeClick(v, record);
                    }
                }
            });
        }
    }


    public interface OnItemClickListener {

        /**
         * 当id被点击
         * @param v
         * @param record
         */
        void onIdClick(View v, Record record);

        /**
         * 当备注被点击
         * @param v
         * @param record
         */
        void onRemarkClick(View v, Record record);

        /**
         * 当创建时间被点击
         * @param v
         * @param record
         */
        void onCreationTimeClick(View v, Record record);
    }
}

运行

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private RecyclerView recyclerView;
    private RecordAdapter adapter;
    private List<Record> records;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        //模拟数据
        records = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            Record record = new Record();
            record.setId(i);
            record.setRemark("第" + i + "条备注");
            record.setCreatedAt(new Date());
            records.add(record);
        }
        adapter = new RecordAdapter(this, records);
        //绑定监听器
        adapter.setOnItemClickListener(new RecordAdapter.OnItemClickListener() {
            @Override
            public void onIdClick(View v, Record record) {
                Toast.makeText(MainActivity.this, record.getId().toString(), Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onRemarkClick(View v, Record record) {
                Toast.makeText(MainActivity.this, record.getRemark(), Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onCreationTimeClick(View v, Record record) {
                Toast.makeText(MainActivity.this, record.getCreatedAt().toString(), Toast.LENGTH_SHORT).show();
            }
        });

        recyclerView.setAdapter(adapter);
    }
}

运行效果如下

运行结果

每个控件的点击效果可以自己亲自测试，接下来同样通过对比的方式讲解封装思路。

RecordAdapter中的回调接口OnItemClickListener

    public interface OnItemClickListener {

        /**
         * 当id被点击
         * @param v
         * @param record
         */
        void onIdClick(View v, Record record);

        /**
         * 当备注被点击
         * @param v
         * @param record
         */
        void onRemarkClick(View v, Record record);

        /**
         * 当创建时间被点击
         * @param v
         * @param record
         */
        void onCreationTimeClick(View v, Record record);
    }

RecordHolder中的控件

        TextView tvId;
        TextView tvRemark;
        TextView tvCreatedAt;

可以看到OnItemClickListener中的抽象方法是和RecordHolder中的控件是一一对应的，而在封装的BaseViewHolder中控件是这样的

        // itemView 中的控件缓存在这里
        private SparseArray<View> views;

那么BaseRecyclerAdapter中的回调接口应该怎么写？
不知道大家用没用过PopupMenu，PopupMenu绑定点击事件如下

popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
    @Override
    public boolean onMenuItemClick(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.view1:
                ...
                break;

            case R.id.view2:
                ...
                break;

            case R.id.view3:
                ...
                break;
        }

        return false;
    }
});

从这里可以获得灵感，为BaseViewHolder中所有的控件都绑定监听器，然后根据控件id的不同来做不同的操作。

BaseRecyclerAdapter中的OnItemClickListener

    /**
     * 回调接口
     * @param <T>
     */
    public interface OnItemClickListener<T> {

        void onItemClick(View view, T t);
    }

BaseViewHolder

class BaseViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

        // itemView 中的控件缓存在这里
        private SparseArray<View> views;
        //数据
        private T t;

        public BaseViewHolder(View itemView) {
            super(itemView);
            views = new SparseArray<>();
        }

        public void setT(T t) {
            this.t = t;
        }

        /**
         * 获取 itemView 中的控件
         *
         * @param id
         * @return
         */
        public View getView(int id) {
            View view = views.get(id);
            if (view == null) {
                view = itemView.findViewById(id);
                views.put(id, view);
                view.setOnClickListener(this);
            }
            return view;
        }

        @Override
        public void onClick(View v) {
            if (onItemClickListener != null) {
                onItemClickListener.onItemClick(v, t);
            }
        }
    }

与之前的BaseViewHolder相比多了几处东西：
1.private T t这个属性以及它的set方法。
2.getView(int id)方法中多了一行代码view.setOnClickListener(this);。
3.onClick方法
这3处代码所做的只有一件事情，就是为private SparseArray<View> views中的所有控件绑定监听器。

BaseRecyclerAdapter也有几处地方需要修改

1.添加成员变量以及它的set方法

    private OnItemClickListener<T> onItemClickListener;

    public void setOnItemClickListener(OnItemClickListener<T> onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

2.修改onBindViewHolder

    @Override
    public void onBindViewHolder(BaseRecyclerAdapter.BaseViewHolder holder, int position) {
        T t = data.get(position);
        holder.setT(t);
        bindData(holder, t);
    }

大功告成

完整代码

public abstract class BaseRecyclerAdapter<T> extends RecyclerView.Adapter<BaseRecyclerAdapter.BaseViewHolder> {

    private OnItemClickListener<T> onItemClickListener;

    //上下文环境
    private Context context;
    //数据集合
    private List<T> data;

    /**
     * 刷新数据
     *
     * @param data
     */
    public void refresh(List<T> data) {
        this.data = data;
        notifyDataSetChanged();
    }

    /**
     * 添加数据
     *
     * @param data
     */
    public void append(List<T> data) {
        this.data.addAll(data);
        notifyDataSetChanged();
    }

    public BaseRecyclerAdapter(Context context, List<T> data) {
        this.context = context;
        this.data = data;
    }

    @Override
    public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(getItemLayoutId(), parent, false);
        return new BaseViewHolder(view);
    }

    @Override
    public void onBindViewHolder(BaseRecyclerAdapter.BaseViewHolder holder, int position) {
        T t = data.get(position);
        holder.setT(t);
        bindData(holder, t);
    }

    @Override
    public int getItemCount() {
        return data == null ? 0 : data.size();
    }

    public void setOnItemClickListener(OnItemClickListener<T> onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

    /**
     * 将数据绑定到itemView视图上
     *
     * @param holder
     * @param t
     */
    public abstract void bindData(BaseViewHolder holder, T t);

    /**
     * 子类通过重写此方法设置itemView项的布局视图
     *
     * @return
     */
    public abstract int getItemLayoutId();

    /**
     * 封装 ViewHolder
     */
    class BaseViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

        // itemView 中的控件缓存在这里
        private SparseArray<View> views;
        //数据
        private T t;

        public BaseViewHolder(View itemView) {
            super(itemView);
            views = new SparseArray<>();
        }

        public void setT(T t) {
            this.t = t;
        }

        /**
         * 获取 itemView 中的控件
         *
         * @param id
         * @return
         */
        public View getView(int id) {
            View view = views.get(id);
            if (view == null) {
                view = itemView.findViewById(id);
                views.put(id, view);
                view.setOnClickListener(this);
            }
            return view;
        }

        @Override
        public void onClick(View v) {
            if (onItemClickListener != null) {
                onItemClickListener.onItemClick(v, t);
            }
        }
    }

    /**
     * 回调接口
     * @param <T>
     */
    public interface OnItemClickListener<T> {

        void onItemClick(View view, T t);
    }
}

使用

将MainActivity中的

        //绑定监听器
        adapter.setOnItemClickListener(new RecordAdapter.OnItemClickListener() {
            @Override
            public void onIdClick(View v, Record record) {
                Toast.makeText(MainActivity.this, record.getId().toString(), Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onRemarkClick(View v, Record record) {
                Toast.makeText(MainActivity.this, record.getRemark(), Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onCreationTimeClick(View v, Record record) {
                Toast.makeText(MainActivity.this, record.getCreatedAt().toString(), Toast.LENGTH_SHORT).show();
            }
        });

替换成

        //绑定监听器
        adapter.setOnItemClickListener(new BaseRecyclerAdapter.OnItemClickListener<Record>() {
            @Override
            public void onItemClick(View view, Record record) {
                switch (view.getId()) {
                    case R.id.tvId:
                        Toast.makeText(MainActivity.this, record.getId().toString(), Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.tvRemark:
                        Toast.makeText(MainActivity.this, record.getRemark(), Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.tvCreatedAt:
                        Toast.makeText(MainActivity.this, record.getCreatedAt().toString(), Toast.LENGTH_SHORT).show();
                        break;
                }
            }
        });

运行效果自己亲自试一试就知道了。