package cn.edu.bzu.util;

import android.content.Context;

import android.util.SparseArray;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

/**

 * Created by monster on 2015/4/20.

 *  Have a good package ViewHolder

 *  get(Context context,View convertView,ViewGroup parent,int layoutId,int position) To make ViewHolder

 *

 */

public class ViewHolder {

    private SparseArray<View> mViews; //稀疏数组，SparseArray比HashMap执行效率高

    private int mPosition;

    private View mConvertView; //作用是方便系统在重写UI时，能重用原来实用过的View实例，以此来降低系统资源的消耗和提高代码效率

    /*

     *ConvertView的几点特征。

     *对于一个ListView，Android保存所有曾经生成过的ConvertView实例，直至系统垃圾回收这些实例位置，而不是只保存最后使用的ConvertView对象。

     *这些保存的ConvertView以使用时间顺序排序，并依次被传递到getView函数中。

     */

    public ViewHolder(Context context,ViewGroup parent,int layoutId,int position){

        //ViewHolder的构造方法

        this.mPosition=position;

        this.mViews=new SparseArray<View>(); //初始化SparseArray对象

        mConvertView= LayoutInflater.from(context).inflate(layoutId,parent,false);

        mConvertView.setTag(this);

    }

    public static ViewHolder get(Context context,View convertView,ViewGroup parent,int layoutId,int position){

        if(convertView==null){

               return new ViewHolder(context,parent,layoutId,position);

        }else{

            ViewHolder holder=(ViewHolder)convertView.getTag();

            holder.mPosition=position;

            return holder;

        }

    }

    /**

     * 通过viewId获取控件

     * @param viewId

     * @param <T>

     * @return

     */

    public <T extends View> T getView(int viewId){

        View view=mViews.get(viewId);

        if(view==null){

            view=mConvertView.findViewById(viewId);

            mViews.put(viewId,view);

        }

        return (T)view;

    }

    public View getConvertView() {

        return mConvertView;

    }

}

package cn.edu.bzu.adapter;

import android.content.Context;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

import android.widget.TextView;

import java.util.List;

import cn.edu.bzu.entity.Bean;

import cn.edu.bzu.listview_demo.R;

import cn.edu.bzu.util.ViewHolder;

/**

 * Created by monster on 2015/4/19.

 */

public class MyAdapterWithCommonViewHolder extends BaseAdapter {

    private LayoutInflater mInflater; //LayoutInflater是用来找layout下xml布局文件，并且实例化

    private List<Bean> mlist;

    private Context mcontext;

    public MyAdapterWithCommonViewHolder(Context context, List<Bean> list) {

        mcontext=context;

        mInflater=LayoutInflater.from(context); //得到初始化上下文

        mlist=list;

    }

    @Override

    public int getCount() {

        return mlist.size();

    }

    @Override

    public Object getItem(int position) {

        return mlist.get(position);

    }

    @Override

    public long getItemId(int position) {

        return position;

    }

    @Override

    public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder holder=ViewHolder.get(mcontext,convertView,parent,R.layout.listview_item,position);

        ((TextView)holder.getView(R.id.id_title)).setText(mlist.get(position).getTitle());

        ((TextView)holder.getView(R.id.id_desc)).setText(mlist.get(position).getDesc());

        ((TextView)holder.getView(R.id.id_time)).setText(mlist.get(position).getDate());

        ((TextView)holder.getView(R.id.id_phone)).setText(mlist.get(position).getPhone());

        return holder.getConvertView();

    }

}