基于ViewHolder优化的BaseAdapt

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利用优化的BaseAdapter来实现一个ListView效果

1.主activity布局文件如下

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">    <ListView        android:layout_width="match_parent"        android:layout_height="match_parent"        android:id="@+id/lv_main"></ListView></RelativeLayout>

2.新建一个滚动条目的布局文件

<?xml version="1.0" encoding="utf-8"?><RelativeLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent">    <ImageView        android:layout_width="60dp"        android:layout_height="60dp"        android:id="@+id/iv_image"        android:src="@mipmap/ic_launcher"/>    <TextView        android:layout_width="match_parent"        android:layout_height="30dp"        android:layout_toRightOf="@id/iv_image"        android:text="title"        android:gravity="center"        android:textSize="20sp"        android:id="@+id/tv_titlt"/>    <TextView        android:layout_width="match_parent"        android:layout_height="30dp"        android:layout_below="@id/tv_titlt"        android:text="content"        android:gravity="center_vertical"        android:textSize="16sp"        android:id="@+id/tv_content"        android:layout_toRightOf="@id/iv_image"        /></RelativeLayout>

3.新建一个javaBean类用于封装要显示的控件

package com.weixi.baseadapter;/** * Created by 风华国乐 on 2016/8/3. */public class ItemBean {    //封装要显示的控件    public int ItemImageResid;    public String ItemTitle;    public String ItemContent;    public ItemBean(int itemImageResid, String itemTitle, String itemContent) {        ItemImageResid = itemImageResid;        ItemTitle = itemTitle;        ItemContent = itemContent;    }}

4.新建Adapter类继承BaseAdapter(适配器)

package com.weixi.baseadapter;import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.ImageView;import android.widget.TextView;import java.util.List;/** * Created by 风华国乐 on 2016/8/3. */public class MyAdapter extends BaseAdapter {    private List<ItemBean> mlist;    private LayoutInflater mInflater;    public MyAdapter(Context context,List<ItemBean> list){       mlist=list;        //context是要使用Adapter的界面对象，mInflater是布局装载器对象        mInflater=LayoutInflater.from(context);    }    //返回所需要的数据数量    @Override    public int getCount() {        return mlist.size();    }    //返回所对应的数据项    @Override    public Object getItem(int position) {        return mlist.get(position);    }    //返回索引对应的数据项    @Override    public long getItemId(int position) {        return position;    }    //返回每一项的显示内容    @Override    public View getView(int position, View convertView, ViewGroup parent) {        //逗逼式，每次都是通过Inflater对象创建一个新的View，并在View中找到相应控件设置相应值，完全没有利用ListView的缓存机制，是对资源的极大浪费//        View view=mInflater.inflate(R.layout.item,null);//        ImageView imageView= (ImageView) view.findViewById(R.id.iv_image);//        TextView title= (TextView) view.findViewById(R.id.tv_titlt);//        TextView content= (TextView) view.findViewById(R.id.tv_content);////        ItemBean bean=mlist.get(position);//        imageView.setImageResource(bean.ItemImageResid);//        title.setText(bean.ItemTitle);//        content.setText(bean.ItemContent);        //return view;        //普通式，利用了ListView的缓存机制//        if (convertView==null){//            //View并未被实例化，缓冲池中无缓存//            convertView=mInflater.inflate(R.layout.item,null);//        }//        ImageView imageView= (ImageView) convertView.findViewById(R.id.iv_image);//       TextView title= (TextView) convertView.findViewById(R.id.tv_titlt);//       TextView content= (TextView) convertView.findViewById(R.id.tv_content);////       ItemBean bean=mlist.get(position);//       imageView.setImageResource(bean.ItemImageResid);//       title.setText(bean.ItemTitle);//       content.setText(bean.ItemContent);//        return convertView;        //文艺式，在文艺式中，我们要避免两个耗时操作，一是重复获取view，二是重复获取findViewById        //不仅 利用了ListView的缓存，更通过ViewHolder类来实现显示数据的视图的缓存，避免多次通过findViewById寻找控件        //首先，创建一个ViewHolder类        class ViewHolder{            public ImageView imageView;            public TextView title;            public TextView content;        }        ViewHolder viewHolder;        if (convertView==null){            viewHolder=new ViewHolder();            viewHolder.imageView=(ImageView) convertView.findViewById(R.id.iv_image);            viewHolder.title=(TextView) convertView.findViewById(R.id.tv_titlt);            viewHolder.content=(TextView) convertView.findViewById(R.id.tv_content);            convertView=mInflater.inflate(R.layout.item,null);            //通过setTag方法将ViewHolder与converview进行关联            convertView.setTag(viewHolder);        }else {            viewHolder= (ViewHolder) convertView.getTag();        }        ItemBean bean=mlist.get(position);        viewHolder.imageView.setImageResource(bean.ItemImageResid);        viewHolder.title.setText(bean.ItemTitle);        viewHolder.content.setText(bean.ItemContent);        return convertView;    }}

5.在主Activity中添加数据，绑定适配器

package com.weixi.baseadapter;import android.os.Bundle;import android.support.v7.app.ActionBarActivity;import android.widget.ListView;import java.util.ArrayList;import java.util.List;public class MainActivity extends ActionBarActivity {   private ListView listview;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        List<ItemBean> itemBeanList=new ArrayList<>();        for (int i = 0; i <20 ; i++) {            itemBeanList.add(new ItemBean(                    R.mipmap.ic_launcher,                    "我是标题"+i,                    "我是内容"+i            ));        }        listview= (ListView) findViewById(R.id.lv_main);        listview.setAdapter(new MyAdapter(this,itemBeanList));    }}

创建思路

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