【Android】以BaseAdapter做适配器的ListView及其性能优化

适配器的Java类

package com.app.adapter;

import org.json.JSONArray;
import org.json.JSONObject;

import android.R.integer;
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 com.app.test01.R;

public class MyWeixinJSON extends BaseAdapter{
    private LayoutInflater mInflater;// 动态布局映射
    private JSONArray list;
    private Context context;
    private int i = 0;
    public MyWeixinJSON(JSONArray list,Context context){
        this.list = list;
        this.context = context;
        this.mInflater = LayoutInflater.from(context);
    }
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return list.length();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return 0;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        convertView = mInflater.inflate(R.layout.item_weixin, null);//根据布局文件实例化view
        try {
            JSONObject jObject = list.getJSONObject(position);

            TextView title = (TextView) convertView.findViewById(R.id.title);//找某个控件
            title.setText(jObject.get("title").toString());//给该控件设置数据(数据从集合类中来)
            TextView time = (TextView) convertView.findViewById(R.id.time);
            time.setText(jObject.get("time").toString());
            TextView info = (TextView) convertView.findViewById(R.id.info);
            info.setText(jObject.get("info").toString());
            ImageView img = (ImageView) convertView.findViewById(R.id.img);
            img.setBackgroundResource((Integer)jObject.get("img"));
        } catch (Exception e) {
            // TODO: handle exception
        }
        return convertView;
    }
}

Activity类

package com.app.test01;

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

import org.json.JSONArray;
import org.json.JSONObject;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;

import com.app.adapter.MyWeixinJSON;
import com.app.adapter.MyWeixinList;

public class ListViewBase extends Activity{
    private ListView lv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.weixin);
        lv = (ListView) findViewById(R.id.lv);
        MyWeixinJSON mJson = new MyWeixinJSON(getJSONArray(),this);
        lv.setAdapter(mJson);
    }
    private JSONArray getJSONArray(){
        JSONArray jsonArray = new JSONArray();
        try {
            for (int i = 1; i <= 30; i++) {
                JSONObject jsonObject = new JSONObject();
                jsonObject.put("title", "姓名"+i);
                jsonObject.put("time", "9月29日");
                jsonObject.put("info", "我通过了你的好友验证请求，现在我们可以开始对话啦");
                jsonObject.put("img", R.drawable.special_spring_head2);
                jsonArray.put(jsonObject);

            }
        } catch (Exception e) {
            // TODO: handle exception
        }
        return jsonArray;
    }
}

ListView的性能优化

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub
    System.out.println("正在渲染第"+position+"行  +++  "+ i++);
    OneView oneView;
    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.item_weixin, null);//根据布局文件实例化view
        oneView = new OneView();
        oneView.title = (TextView) convertView.findViewById(R.id.title);//找某个控件
        oneView.time = (TextView) convertView.findViewById(R.id.time);
        oneView.info = (TextView) convertView.findViewById(R.id.info);
        oneView.img = (ImageView) convertView.findViewById(R.id.img);
        convertView.setTag(oneView);//把View和某个对象关联起来
    } else {
        oneView = (OneView) convertView.getTag();
    }
    JSONObject jObject = null;
    try {
        jObject = list.getJSONObject(position);//根据position获取集合类中某行数据
        oneView.title.setText(jObject.get("title").toString());//给该控件设置数据(数据从集合类中来)
        oneView.time.setText(jObject.get("time").toString());
        oneView.info.setText(jObject.get("info").toString());
        oneView.img.setBackgroundResource((Integer)jObject.get("img"));
    } catch (Exception e) {
        // TODO: handle exception
    }
    return convertView;
}
/** 把每行布局文件的各个控件包装成一个对象  */
private class OneView{
    TextView title;
    TextView time;
    TextView info;
    ImageView img;
}