Android BaseAdapter的使用

现在有许多的适配器供我们使用，但是我们发现处理复杂的itmes使往往使用的是BaseAdapter，下面上代码

main.xml

xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/lv"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:fastScrollEnabled="true"
        />

LinearLayout>

list_item.xml

xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

    <ImageView
        android:id="@+id/img"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
    <LinearLayout 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        >
        <TextView
            android:id="@+id/tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="20sp"
        />
        <TextView 
            android:id="@+id/info"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="14sp"
            />
    LinearLayout>


LinearLayout>

Activity

package com.loulijun.demo17;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

public class Demo17Activity extends Activity {
    private ListView lv;
    private List> data;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        lv = (ListView)findViewById(R.id.lv);
        //获取将要绑定的数据设置到data中
        data = getData();
        MyAdapter adapter = new MyAdapter(this);
        lv.setAdapter(adapter);
    }

    private List> getData()
    {
        List> list = new ArrayList>();
        Map map;
        for(int i=0;i<10;i++)
        {
            map = new HashMap();
            map.put("img", R.drawable.ic_launcher);
            map.put("title", "跆拳道");
            map.put("info", "快乐源于生活...");
            list.add(map);
        }
        return list;
    }

    //ViewHolder静态类
    static class ViewHolder {
        public ImageView img;
        public TextView title;
        public TextView info;
    }

    public class MyAdapter extends BaseAdapter {    
        private LayoutInflater mInflater = null;
        private MyAdapter(Context context) {
            //根据context上下文加载布局，这里的是Demo17Activity本身，即this
            this.mInflater = LayoutInflater.from(context);
        }

        @Override
        public int getCount() {
            //How many items are in the data set represented by this Adapter.
            //在此适配器中所代表的数据集中的条目数
            return data.size();
        }

        @Override
        public Object getItem(int position) {
            // Get the data item associated with the specified position in the data set.
            //获取数据集中与指定索引对应的数据项
            return position;
        }

        @Override
        public long getItemId(int position) {
            //Get the row id associated with the specified position in the list.
            //获取在列表中与指定索引对应的行id
            return position;
        }

        //Get a View that displays the data at the specified position in the data set.
        //获取一个在数据集中指定索引的视图来显示数据
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder holder = null;
            //如果缓存convertView为空，则需要创建View
            if(convertView == null)
            {
                holder = new ViewHolder();
                //根据自定义的Item布局加载布局
                convertView = mInflater.inflate(R.layout.list_item, null);
                holder.img = (ImageView)convertView.findViewById(R.id.img);
                holder.title = (TextView)convertView.findViewById(R.id.tv);
                holder.info = (TextView)convertView.findViewById(R.id.info);
                //将设置好的布局保存到缓存中，并将其设置在Tag里，以便后面方便取出Tag
                convertView.setTag(holder);
            }else
            {
                holder = (ViewHolder)convertView.getTag();
            }
            holder.img.setBackgroundResource((Integer)data.get(position).get("img"));
            holder.title.setText((String)data.get(position).get("title"));
            holder.info.setText((String)data.get(position).get("info"));

            return convertView;
        }

    }
}

运行结果如下：