RecyclerView通用适配器的实现

分析

• 我们需要在RecyclerViewAdapter内部维持一个数据集合的引用
• 需要实现Item的点击事件，包括短按和长按，并需要向外部提供设置监听器的方法
• 这个适配器必须通用，所以应该是泛型的，并且ViewHolder也是通用的，可以采用SparseArray维持View的所有集合
• 在RecyclerViewAdapter内部需要实现数据的绑定（抽象方法，延迟到子类实现），监听器的绑定

编写监听器

分为短按事件和长按事件

• 短按监听器

package cn.edu.zafu.base.adapter.listener;

import android.view.View;

/**
 * Created by lizhangqu on 2015/6/3.
 */
public interface OnItemClickListener<T> {
    void onClick(View view, T item);
}

• 长按监听器

package cn.edu.zafu.base.adapter.listener;

import android.view.View;

/**
 * Created by lizhangqu on 2015/6/3.
 */
public interface OnItemLongClickListener<T> {
    void onLongClick(View view, T item);
}

编写通用适配器

• 设置监听器

package cn.edu.zafu.base.adapter;

import android.support.v7.widget.RecyclerView;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.List;

import cn.edu.zafu.base.adapter.listener.OnItemClickListener;
import cn.edu.zafu.base.adapter.listener.OnItemLongClickListener;

/**
 * this is a BaseAdapter for RecyclerView
 * author lizhangqu
 * version 1.0
 * date 2015/6/3.
 */
public abstract class BaseRecyclerViewAdapter<T, VH extends BaseRecyclerViewAdapter.SparseArrayViewHolder> extends RecyclerView.Adapter<VH> {

    /**
     * click listener
     */
    protected OnItemClickListener mOnItemClickListener;
    /**
     * long click listener
     */
    protected OnItemLongClickListener mOnItemLongClickListener;

    /**
     * set a long click listener
     *
     * @param onItemLongClickListener
     */
    public void setOnItemLongClickListener(OnItemLongClickListener onItemLongClickListener) {
        mOnItemLongClickListener = onItemLongClickListener;
    }

    /**
     * set a click listener
     *
     * @param onItemClickListener
     */
    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        mOnItemClickListener = onItemClickListener;
    }

}

• 编写构造方法，将数据集合进行赋值

    /**
     * data
     */
    protected List<T> mList;

    /**
     * @param list the datas to attach the adapter
     */
    public BaseRecyclerViewAdapter(List<T> list) {
        mList = list;
    }

• 实现几个必要的方法，比如获得Item以及覆写getItemCount方法

   /**
   * get a item by index
   *
   * @param position
   * @return
   */
  protected T getItem(int position) {
      return mList.get(position);
  }
  
  @Override
  public int getItemCount() {
      return mList.size();
  }
  

• 实现将布局文件映射成View的方法

   /**
     * inflate a view by viewgroup ,id ,etc
     *
     * @param viewGroup
     * @param layoutId
     * @return
     */
    protected View inflateItemView(ViewGroup viewGroup, int layoutId) {
        return inflateItemView(viewGroup, layoutId, false);
    }

    /**
     * inflate a view by viewgroup ,id ,etc
     *
     * @param viewGroup
     * @param layoutId
     * @param attach
     * @return
     */
    protected View inflateItemView(ViewGroup viewGroup, int layoutId, boolean attach) {
        return LayoutInflater.from(viewGroup.getContext()).inflate(layoutId, viewGroup, attach);
    }

• 实现onBindViewHolder方法，这一步很重要，将具体实现抽取到两个方法中去实现，bindDataToItemView是一个抽象方法，延迟到子类实现，bindItemViewClickListener方法设置监听器

  /**
     * a final function to avoid you override
     * use template design pattern
     *
     * @param vh
     * @param position
     */
    @Override
    public final void onBindViewHolder(VH vh, int position) {
        final T item = getItem(position);
        bindDataToItemView(vh, item);
        bindItemViewClickListener(vh, item);
    }

    /**
     * bind data to itemview
     *
     * @param vh   viewholder
     * @param item item
     */
    protected abstract void bindDataToItemView(VH vh, T item);
    /**
     * bind click listner to itemview
     *
     * @param vh   viewholder
     * @param item item
     */
    protected final void bindItemViewClickListener(VH vh, final T item) {
        if (mOnItemClickListener != null) {
            vh.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    mOnItemClickListener.onClick(view, item);
                }
            });
        }
        if (mOnItemLongClickListener != null) {
            vh.itemView.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    mOnItemLongClickListener.onLongClick(v, item);
                    return true;
                }
            });
        }
    }

• 实现通用ViewHolder，内部使用SparseArray维持View对象

    public static class SparseArrayViewHolder extends RecyclerView.ViewHolder {
        private final SparseArray<View> views;

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

        public <T extends View> T getView(int id) {
            View view = views.get(id);
            if (view == null) {
                view = itemView.findViewById(id);
                views.put(id, view);
            }
            return (T) view;
        }
    }

内部实现了一个泛型的getView方法，其作用就是将View缓存至SparseArray中去

• 实现通用ViewHolder的一些属性设置方法，采用链式调用，返回this对象

        public SparseArrayViewHolder setText(int viewId, String value) {
            TextView view = getView(viewId);
            view.setText(value);
            return SparseArrayViewHolder.this;
        }

        public SparseArrayViewHolder setTextColor(int viewId, int textColor) {
            TextView view = getView(viewId);
            view.setTextColor(textColor);
            return SparseArrayViewHolder.this;
        }

        public SparseArrayViewHolder setImageResource(int viewId, int imageResId) {
            ImageView view = getView(viewId);
            view.setImageResource(imageResId);
            return SparseArrayViewHolder.this;
        }

        public SparseArrayViewHolder setBackgroundColor(int viewId, int color) {
            View view = getView(viewId);
            view.setBackgroundColor(color);
            return SparseArrayViewHolder.this;
        }

        public SparseArrayViewHolder setBackgroundResource(int viewId, int backgroundRes) {
            View view = getView(viewId);
            view.setBackgroundResource(backgroundRes);
            return SparseArrayViewHolder.this;
        }

        public SparseArrayViewHolder setVisible(int viewId, boolean visible) {
            View view = getView(viewId);
            view.setVisibility(visible ? View.VISIBLE : View.GONE);
            return SparseArrayViewHolder.this;
        }

        public SparseArrayViewHolder setOnClickListener(int viewId, View.OnClickListener listener) {
            View view = getView(viewId);
            view.setOnClickListener(listener);
            return SparseArrayViewHolder.this;
        }

        public SparseArrayViewHolder setOnTouchListener(int viewId, View.OnTouchListener listener) {
            View view = getView(viewId);
            view.setOnTouchListener(listener);
            return SparseArrayViewHolder.this;
        }

        public SparseArrayViewHolder setOnLongClickListener(int viewId, View.OnLongClickListener listener) {
            View view = getView(viewId);
            view.setOnLongClickListener(listener);
            return SparseArrayViewHolder.this;
        }

        public SparseArrayViewHolder setTag(int viewId, Object tag) {
            View view = getView(viewId);
            view.setTag(tag);
            return SparseArrayViewHolder.this;
        }

源码

• 参见github地址：https://github.com/lizhangqu