Listview实现分页下载

分析:
 *    1.初始控件,展示第一页数据
 *    2.设置触发条件
 *        1.设置滚动监听
 *        2.判断是否在底部
 *        3.判断是否停止滚动
 *        4.更改网络请求参数为下一页
 *        5.异步网络请求
 *        6.解析成新的集合
 *        7.把新的集合添加到之前的集合中
 *        8.更新数据
 *    3.添加 加载过程中对话框提示正在加载的功能

layout.xml

<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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <ListView 
        android:id="@+id/listView"
        android:layout_height="match_parent"
        android:layout_width="wrap_content"></ListView>

</RelativeLayout>

listview_news.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" >
    <TextView 
        android:id="@+id/tv_sublect"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
     />
    <ImageView 
        android:id="@+id/img_cover"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    

</LinearLayout>

HttpUtils.java

package HttpUtils;

import java.io.IOException;
import java.io.StringReader;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

public class HttpUtils {
    //从网络下载json数据
    public static String getJsonDataByIntetnet(String path){
        byte[] buffer= getByteArrayByIntetnet(path);
        if(buffer != null && buffer.length != 0){
            return new String(buffer);
        }
        return null;
        
    }
    //从网络获取字节数组
    public static byte[] getByteArrayByIntetnet(String path){
        try {
            DefaultHttpClient client = new  DefaultHttpClient();
            HttpGet httpGet = new HttpGet(path);
            HttpResponse httpResponse = client.execute(httpGet);
            if(200 == httpResponse.getStatusLine().getStatusCode()){
                HttpEntity entity = httpResponse.getEntity();
                return EntityUtils.toByteArray(entity);
            }
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }return null;

    }
    //从网络上获取Bitmap对象
    public static Bitmap getBitmapByIntetnet(byte[] byteArray){
        if(byteArray != null && byteArray.length != 0){
          return BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);
        }
        return null;
        
    }
}

ParseJson.java

package parserJson;

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

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

import com.example.News;

public class ParserJson {
    public static List<News> parseJson(String json){
        try {
            JSONObject jsonObject = new JSONObject(json);
            JSONObject jsonObject2 = jsonObject.getJSONObject("paramz");
            JSONArray jsonArray = jsonObject2.getJSONArray("feeds");
            List<News>dataList = new ArrayList<News>();
            News news;
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject jsonObject3 = jsonArray.getJSONObject(i);
                news = new News();
                JSONObject jsonObject4 = jsonObject3.getJSONObject("data");
                news.setTv_subject(jsonObject4.getString("subject"));
                news.setImg_cover(jsonObject4.getString("cover"));
                dataList.add(news);
            }
            return dataList;
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
        
        
        
    }
}

Constants.java

package com.example;
/**
 * 将需要下载数据的网址隔开,实现分页下载的目的
 * @author my
 *
 */
public class Constants {
    public static final String pathBefore="http://litchiapi.jstv.com/api/GetFeeds?column=0&PageSize=10&pageIndex=";
    public  static final String pathAfter = "&val=100511D3BE5301280E0992C73A9DEC41";
}

News.java

package com.example;
/**
 * 新闻类
 * @author my
 *
 */
public class News {
    private String tv_subject;
    private String img_cover;
    public String getTv_subject() {
        return tv_subject;
    }
    public void setTv_subject(String tv_subject) {
        this.tv_subject = tv_subject;
    }
    public String getImg_cover() {
        return img_cover;
    }
    public void setImg_cover(String img_cover) {
        this.img_cover = img_cover;
    }
    @Override
    public String toString() {
        return "News [tv_subject=" + tv_subject + ", img_cover=" + img_cover
                + "]";
    }
    
    
}

UpdateNewView.java

package com.example;

import java.util.List;

/**
 * 更新视图
 * @author my
 *
 */
public interface UpdateNewView {
    public void updateNewView(List<News> dataList);
}

UpdateImageView.java

package com.example;

import android.graphics.Bitmap;
/**
 * 更新图片
 * @author my
 *
 */
public interface UpdateImageView {
    public void updateImageView(Bitmap bitmap);
}

DownLoadData_AsyncTask.java

package com.example;

import java.util.List;

import parserJson.ParserJson;
import HttpUtils.HttpUtils;
import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.util.Log;
/**
 * 异步任务类下载数据
 * @author my
 *
 */
public class MyAsyncTask extends AsyncTask<String, Integer, List<News>>{
    private Context context;
    private UpdateNewView updateNewView;
    private String TAG = "MainActivity";
    private ProgressDialog progressDialog;
    
    public MyAsyncTask(Context context, UpdateNewView updateNewView) {
        super();
        this.context = context;
        this.updateNewView = updateNewView;
    }
    /**
     * 在执行异步下载之前调用
     */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        //创建进度条对话框
        progressDialog = new ProgressDialog(context);
        //设置标题
        progressDialog.setTitle("加载数据");
        //设置信息
        progressDialog.setMessage("玩命加载...");
        //进度条展示
        progressDialog.show();
    }
    /**
     * 执行异步下载数据操作
     */
    @Override
    protected List<News> doInBackground(String... params) {
        //从网络获取json数据
        String jsonDataByIntetnet = HttpUtils.getJsonDataByIntetnet(params[0]);
        //解析json数据到集合
        List<News> dataList = ParserJson.parseJson(jsonDataByIntetnet);
        
        return dataList;
    }
    /**
     * 接收doInBacground传过来的数据,并回传给接口的实现方法中
     */
    @Override
    protected void onPostExecute(List<News> result) {
        super.onPostExecute(result);
        //移除对话框,展示页面
        progressDialog.dismiss();
        if(result != null && result.size() != 0){
            updateNewView.updateNewView(result);//接口回调
        }
    }
}

DownLoadImg_AsyncTask.java

package com.example;

import HttpUtils.HttpUtils;
import android.graphics.Bitmap;
import android.os.AsyncTask;
/**
 * 异步任务实现类下载图片
 * @author my
 *
 */
public class DownLoadImgAsyncTask extends AsyncTask<String, Integer, Bitmap>{
    private UpdateImageView updateImageView;
    

    public DownLoadImgAsyncTask(UpdateImageView updateImageView) {
        super();
        this.updateImageView = updateImageView;
    }
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }
    @Override
    protected Bitmap doInBackground(String... params) {
        byte[] byteArrayByIntetnet = HttpUtils.getByteArrayByIntetnet(params[0]);
        Bitmap bitmapByIntetnet = HttpUtils.getBitmapByIntetnet(byteArrayByIntetnet);
        
        return bitmapByIntetnet;
    }
    @Override
    protected void onPostExecute(Bitmap result) {
        super.onPostExecute(result);
        if(result != null ){
            updateImageView.updateImageView(result);
        }
    }
}

Main.java

package com.example;

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

import com.example.day09_listview_page.R;
import com.example.day09_listview_page.R.drawable;
import com.example.day09_listview_page.R.id;
import com.example.day09_listview_page.R.layout;

import android.os.Bundle;
import android.app.Activity;
import android.graphics.Bitmap;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends Activity {
    private int index = 1;
    private ListView listView;
    private boolean isBottom;
    private MyAdapter adapter;
    //设置数据集合
    private List<News> dataList1 = new ArrayList<News>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化控件
        listView = (ListView) findViewById(R.id.listView);
        //设置数据
        /**
         * 创建异步任务下载数据
         */
        new MyAsyncTask(MainActivity.this,new UpdateNewView() {

            
            @Override
            public void updateNewView(List<News> dataList) {
                //填充第一页数据
                dataList1.remove(dataList1);
                dataList1.addAll(dataList);
                //创建适配器
                adapter = new MyAdapter();
                //适配器控件设置适配器
                listView.setAdapter(adapter);
            }
        }).execute(Constants.pathBefore+index+Constants.pathAfter);
        /**
         * 设置listView滚动监听事件:添加新的页面的数据
         */
        listView.setOnScrollListener(new OnScrollListener() {
            /**
             * 当滚动状态改变的时候调用
             */
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                //滚动停止并且页面滑动到底部,执行异步下载下一页的操作
                if(scrollState==SCROLL_STATE_IDLE && isBottom){
                    index += 1;//页数加1
                    new MyAsyncTask(MainActivity.this,new UpdateNewView() {
                        @Override
                        public void updateNewView(List<News> dataList) {
                            dataList1.addAll(dataList1);//添加回传过来的集合
                            adapter.notifyDataSetChanged();//通知刷新数据,listview里面的item发生变化时调用该方法更新数据
                        }
                    }).execute(Constants.pathBefore+index+Constants.pathAfter);
                }
            
            }
            /**
             * 当listView滚动的时候调用
             */
            @Override
            public void onScroll(AbsListView view, int firstVisibleItem,
                    int visibleItemCount, int totalItemCount) {
                    isBottom =(firstVisibleItem + visibleItemCount==totalItemCount) ;
                
            }
        });
        
        
    }
    class MyAdapter extends BaseAdapter{

        @Override
        public int getCount() {
            return dataList1.size();
        }

        @Override
        public Object getItem(int position) {
            return dataList1.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }
        //为适配器控件的每条item的view组件设置数据
        @Override
        public View getView(int position, View convertView, final ViewGroup parent) {
            View view = convertView;
            final ViewHolder viewHolder;
            if(view == null){
                view= View.inflate(MainActivity.this, R.layout.listview_news, null);
                viewHolder = new ViewHolder();
                viewHolder.tv_subject = (TextView)view.findViewById(R.id.tv_sublect);
                viewHolder.img_cover = (ImageView) view.findViewById(R.id.img_cover);
                view.setTag(viewHolder);
            }else{
                viewHolder = (ViewHolder) view.getTag();
            }
            News news = dataList1.get(position);
            viewHolder.tv_subject.setText(news.getTv_subject());
            //设置默认图片
            viewHolder.img_cover.setImageResource(R.drawable.ic_launcher);
            final String imgPath = news.getImg_cover();
            //解决图片错乱问题,给图片设置一个标记
            viewHolder.img_cover.setTag(imgPath);
            //创建一个异步任务下载图片
            new DownLoadImgAsyncTask(new UpdateImageView() {
                
                @Override
                public void updateImageView(Bitmap bitmap) {
                    //适配器控件通过标记找到view控件
                     ImageView imageView= (ImageView) parent.findViewWithTag(imgPath);
                     //设置图片
　　　　　　　　　　　　if(iamgeView != null){
                     　　imageView.setImageBitmap(bitmap);
　　　　　　　　　　　　}
                }
            }).execute(imgPath);
            return view;
        }
        
    }
    class ViewHolder{
        private TextView tv_subject;
        private ImageView img_cover;
    }

}