前言

昨天开始接触江湖口碑很好的RecyclerView，事实上，我已经被她的强大所征服了！资源回收，数据绑定，布局显示，分割线，Item动画多个模块高度解耦，灵活优雅。其实，RecyclerView在使用上已经是相当简单了（个人觉得），但仍有很多代码是可以加以封装的。今天受简书上一篇博文的启发，作为写代码喜欢优（tou）雅（lan）的人，想到了一种封装方式，打造万能适配器，供大家食用。

正统模式：

public class SimplerItemAdapter extends RecyclerView.Adapter<SimplerItemAdapter.SimpleItemViewHolder > {      private List <String> items;      public SimplerItemAdapter (@NonNull List<String> dateItems ) {      this.items = (dateItems != null ? dateItems : new ArrayList<String>());    }      @Override public SimpleItemViewHolder onCreateViewHolder (ViewGroup viewGroup, int viewType) {      View itemView = LayoutInflater.from( viewGroup.getContext ()).inflate(R.layout .item, viewGroup, false );      return new SimpleItemViewHolder(itemView);    }      @Override public void onBindViewHolder (SimpleItemViewHolder viewHolder, int position) {      viewHolder.textView .setText(items.get (position));    }      @Override public int getItemCount () {      return (this.items != null) ? this .items. size() : 0 ;    }      protected final static class SimpleItemViewHolder extends RecyclerView.ViewHolder {      protected TextView textView ;        public SimpleItemViewHolder (View itemView) {        super(itemView);        this.textView = (TextView) itemView.findViewById (R. id.text);      }    }  }

• 首先，
  @Override public int getItemCount () {
return (this.items != null) ? this .items. size() : 0 ;
}这段代码完全可以封装起来的。
• onCreatedViewHolder()方法作用是绑定item视图，可以进一步封装，给子类提供一个getLayoutItemId的抽象方法，这样就可以简化成一行代码了。
• 因此我们发现，这个adapter的核心代码在与onBindViewHolder（）中，作用是将数据跟视图（ViewHolder）绑定，可以给子类提供一个bindData（）抽象方法。
• 当然了，使用泛型也是极好的，拓广了adapter的使用范围。
• 添加点击事件的监听也可以封装到万能adapter中，子类就不用再写item点击事件处理代码了

封装后的Adapter

public abstract class BaseRecyclerAdapter<T> extends RecyclerView.Adapter<RecyclerViewHolder> {      protected final List<T> mData;      protected final Context mContext;      protected LayoutInflater mInflater;      private OnItemClickListener mClickListener;      private OnItemLongClickListener mLongClickListener;        public BaseRecyclerAdapter(Context ctx, List<T> list) {          mData = (list != null) ? list : new ArrayList<T>();          mContext = ctx;          mInflater = LayoutInflater.from(ctx);      }        @Override      public RecyclerViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {          final RecyclerViewHolder holder = new RecyclerViewHolder(mContext,                  mInflater.inflate(getItemLayoutId(viewType), parent, false));          if (mClickListener != null) {              holder.itemView.setOnClickListener(new View.OnClickListener() {                  @Override                  public void onClick(View v) {                      mClickListener.onItemClick(holder.itemView, holder.getLayoutPosition());                  }              });          }          if (mLongClickListener != null) {              holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {                  @Override                  public boolean onLongClick(View v) {                      mLongClickListener.onItemLongClick(holder.itemView, holder.getLayoutPosition());                      return true;                  }              });          }          return holder;      }        @Override      public void onBindViewHolder(RecyclerViewHolder holder, int position) {          bindData(holder, position, mData.get(position));      }        @Override      public int getItemCount() {          return mData.size();      }        public void add(int pos, T item) {          mData.add(pos, item);          notifyItemInserted(pos);      }        public void delete(int pos) {          mData.remove(pos);          notifyItemRemoved(pos);      }        public void setOnItemClickListener(OnItemClickListener listener) {          mClickListener = listener;      }        public void setOnItemLongClickListener(OnItemLongClickListener listener) {          mLongClickListener = listener;      }        abstract public int getItemLayoutId(int viewType);        abstract public void bindData(RecyclerViewHolder holder, int position, T item);        public interface OnItemClickListener {          public void onItemClick(View itemView, int pos);      }        public interface OnItemLongClickListener {          public void onItemLongClick(View itemView, int pos);      }  }

Super ViewHolder！

其实，这还没完呢！重头戏在ViewHolder上！RecyclerView强制我们使用ViewHolder模式，然而缺不可避免地要写findViewById代码，有没有办法不写这样的代码呢？甚至连ViewHolder都不写呢？当然可以！

public class RecyclerViewHolder extends RecyclerView.ViewHolder {      private SparseArray<View> mViews;//集合类，layout里包含的View,以view的id作为key，value是view对象      private Context mContext;//上下文对象        public RecyclerViewHolder(Context ctx, View itemView) {          super(itemView);          mContext = ctx;          mViews = new SparseArray<View>();      }        private <T extends View> T findViewById(int viewId) {          View view = mViews.get(viewId);          if (view == null) {              view = itemView.findViewById(viewId);              mViews.put(viewId, view);          }          return (T) view;      }        public View getView(int viewId) {          return findViewById(viewId);      }        public TextView getTextView(int viewId) {          return (TextView) getView(viewId);      }        public Button getButton(int viewId) {          return (Button) getView(viewId);      }        public ImageView getImageView(int viewId) {          return (ImageView) getView(viewId);      }        public ImageButton getImageButton(int viewId) {          return (ImageButton) getView(viewId);      }        public EditText getEditText(int viewId) {          return (EditText) getView(viewId);      }        public RecyclerViewHolder setText(int viewId, String value) {          TextView view = findViewById(viewId);          view.setText(value);          return this;      }        public RecyclerViewHolder setBackground(int viewId, int resId) {          View view = findViewById(viewId);          view.setBackgroundResource(resId);          return this;      }        public RecyclerViewHolder setClickListener(int viewId, View.OnClickListener listener) {          View view = findViewById(viewId);          view.setOnClickListener(listener);          return this;      }  }

该类的核心方法是private T findViewById(int viewId)，核心成员变量是private SparseArray mViews; 不信可以不写一句ViewHolder代码？接下来看看用法。

实践用法

添加Adapter仅需短短的几行代码：

Adapter = new BaseRecyclerAdapter<String>(this,mDataList) {              @Override              public int getItemLayoutId(int viewType) {                  return R.layout.item;              }              @Override              public void bindData(RecyclerViewHolder holder, int position,String item) {                  //调用holder.getView(),getXXX()方法根据id得到控件实例，进行数据绑定即可                  holder.setText(R.id.tv_num,item)                          .getTextView(R.id.tv_title,item).setText(item);              }          };

完整代码：

    private void init() {          recyclerView = (RecyclerView) findViewById(R.id.recyclerView);          mDataList = new ArrayList<>();          for (int i = 0; i <= 100; i++) {              mDataList.add(String.valueOf(i));          }          //设置item动画          recyclerView.setItemAnimator(new DefaultItemAnimator());          mAdapter = new BaseRecyclerAdapter<String>(this,mDataList) {              @Override              public int getItemLayoutId(int viewType) {                  return R.layout.item;              }              @Override              public void bindData(RecyclerViewHolder holder, int position,String item) {                  //调用holder.getView(),getXXX()方法根据id得到控件实例，进行数据绑定即可                  holder.setText(R.id.tv_num,item)                          .getTextView(R.id.tv_title,item).setText(item);              }          };          recyclerView.setAdapter(mAdapter);          //添加item点击事件监听          ((BaseRecyclerAdapter)mAdapter).setOnItemClickListener(new BaseRecyclerAdapter.OnItemClickListener() {              @Override              public void onItemClick(View itemView, int pos) {                  Toast.makeText(AdapterTestActivity.this, "click " + pos, Toast.LENGTH_SHORT).show();              }          });          ((BaseRecyclerAdapter)mAdapter).setOnItemLongClickListener(new BaseRecyclerAdapter.OnItemLongClickListener() {              @Override              public void onItemLongClick(View itemView, int pos) {                  Toast.makeText(AdapterTestActivity.this, "long click " + pos, Toast.LENGTH_SHORT).show();              }          });          //设置布局样式LayoutManager          recyclerView.setLayoutManager(new LinearLayoutManager(AdapterTestActivity.this, LinearLayoutManager.VERTICAL, false));  // recyclerView.addItemDecoration(new ItemDividerDecoration(MainActivity.this, OrientationHelper.VERTICAL));        }

如果觉得有什么不妥之处或建议，敬请指教！
完整项目代码已上传至Github。—Github跳转。

see also：
Listview的Adapter应该这样写