Android学习笔记（十）——实现新闻列表

【第一部分】历史文章：
Android学习笔记（一）——创建第一个Android项目
Android学习笔记（二）android studio基本控件及布局（实现图片查看器）
Android学习笔记（三）android studio中CheckBox自定义样式（更换复选框左侧的勾选图像）
Android学习笔记（四）Android 中Activity页面的跳转及传值
Android学习笔记（五）——Toast提示、Dialog对话框、Menu菜单
Android学习笔记（六）——自定义ListView布局+AsyncTask异步任务
Android学习笔记（七）——数据存储（共享参数SharedPreferences）
Android学习笔记（八）——数据存储（SD卡文件操作）
Android学习笔记（九）——网络技术
【第二部分】主要问题解决：
Android Studio（存）读取不了SD卡上的文件——【已解决】

在上一篇的网络技术的文章中，主要介绍了数据的获取，没有对数据进行解析。那么这篇文章，用一个综合的案例，介绍数据的解析及以前知识的应用。

首先我们拿到头条新闻的api接口地址：Http://v.juhe.cn/toutiao/index?type=top&key=a1a755458cc22f129942b34904feb820

new_item_layout.xml

news.java

package cn.edu.hznu.ex10_news.bean;
public class News {
    private String title;  //标题
    private String date;   //时间
    private String author_name;   //来源——作者名字
    private String thumbnail_pic_s;   //头像
    private String url;     //具体的内容
    public String getTitle() {
        return title;
    }
public void setTitle(String title) {
        this.title = title;
    }
    public String getDate() {
        return date;
    }
    public void setDate(String date) {
        this.date = date;
    }
    public String getAuthor_name() {
        return author_name;
    }
    public void setAuthor_name(String author_name) {
        this.author_name = author_name;
    }
    public String getThumbnail_pic_s() {
        return thumbnail_pic_s;
    }
    public void setThumbnail_pic_s(String thumbnail_pic_s) {
        this.thumbnail_pic_s = thumbnail_pic_s;
    }
    public String getUrl() {
        return url;
    }
    public void setUrl(String url) {
        this.url = url;
    }
}

jsONUtils.java

package cn.edu.hznu.ex10_news.utils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import cn.edu.hznu.ex10_news.bean.News;
public class JSONUtils {
    public static ArrayList parseJson(String jsonData) {
        ArrayList result = new ArrayList();
        JSONObject jo = null;
        News news;
        try {
            jo = new JSONObject(jsonData);
            if (jo.getString("reason").equals("成功的返回")) {
                JSONObject jo1 = jo.getJSONObject("result");
                JSONArray ja = jo1.getJSONArray("data");
                for (int i = 0; i < ja.length(); i++) {
                    news = new News();
                    JSONObject obj = ja.getJSONObject(i);
                    news.setTitle(obj.getString("title"));
                    news.setDate(obj.getString("date"));
                    news.setAuthor_name(obj.getString("author_name"));
                    news.setThumbnail_pic_s(obj.getString("thumbnail_pic_s"));
                    news.setUrl(obj.getString("url"));
                    result.add(news);
                }
            }
            return  result;
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return null;
    }
}

NewsTask.java

package cn.edu.hznu.ex10_news.task;
import android.os.AsyncTask;
import java.io.IOException;
import java.util.ArrayList;
import cn.edu.hznu.ex10_news.bean.News;
import cn.edu.hznu.ex10_news.utils.JSONUtils;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
public class NewsTask  extends AsyncTask<String,Void,ArrayList> {
    private NewsCallBack  newsCallBack;
    public NewsTask(NewsCallBack newsCallBack) {
        this.newsCallBack = newsCallBack;
    }
    @Override
    protected ArrayList doInBackground(String... strings) {
        /
        options.inJustDecodeBounds = true;
        img_bitmap = BitmapFactory.decodeByteArray(imageData,0,imageData.length, options);
        options.inJustDecodeBounds = false;//设为 false
        //计算缩放比
        int h = options.outHeight;
        int w = options.outWidth;
        int beWidth = w / width;
        int beHeight = h / height;
        int be = 1;
        if (beWidth < beHeight) {
            be = beWidth;
        } else {
            be = beHeight;
        }
        if (be <= 0) {
            be = 1;
        }
        options.inSampleSize = be;
        img_bitmap = BitmapFactory.decodeByteArray(imageData,0,imageData.length, options);
        img_bitmap = ThumbnailUtils.extractThumbnail(img_bitmap, width, height,
                ThumbnailUtils.OPTIONS_RECYCLE_INPUT);
        return img_bitmap;
    }
}

NewsAdapter .java

package cn.edu.hznu.ex10_news.adapter;
import android.content.Context;
import android.graphics.Bitmap;
import android.support.annotation.NonNull;
import android.text.TextUtils;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.List;
import cn.edu.hznu.ex10_news.R;
import cn.edu.hznu.ex10_news.bean.News;
import cn.edu.hznu.ex10_news.task.ImageTask;
public class NewsAdapter extends ArrayAdapter {
    private int item_layout_id;
    public NewsAdapter(Context context, int resource, List objects) {
        super(context, resource,objects);
        item_layout_id=resource;
    }
    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view=null;
        final  ViewHolder holder;
        if(convertView==null){//回收站为空\
            
            view= LayoutInflater.from(getContext())
                    .inflate(item_layout_id,parent,false);
            holder=new ViewHolder(view);
            view.setTag(holder);
        }else {//显示后续的列表项
            view=convertView;
            holder= (ViewHolder) view.getTag();
        }
        News itemData=getItem(position);
        holder.title.setText(itemData.getTitle());
        holder.date.setText(itemData.getDate());
        holder.author_name.setText(itemData.getAuthor_name());
        if(!TextUtils.isEmpty(itemData.getThumbnail_pic_s())){
            new ImageTask(new ImageTask.CallBack() {
                @Override
                public void getResults(Bitmap result) {
                    holder.thumbnail_pic_s.setImageBitmap(result);
                }
            }).execute(itemData.getThumbnail_pic_s()) ;  //执行异步任务
        }else{
            holder.thumbnail_pic_s.setVisibility(View.GoNE);
        }
        return view;
    }
    class  ViewHolder{
        TextView title;
        TextView date;
        TextView author_name;
        ImageView thumbnail_pic_s;
        public ViewHolder(View view) {
            title=(TextView) view.findViewById(R.id.title);
            date=(TextView)view.findViewById(R.id.date);
            author_name=(TextView)view.findViewById(R.id.author_name);
            thumbnail_pic_s=(ImageView)view.findViewById(R.id.imgsrc);
        }
    }
}

异步任务结合进度显示，，可以很好的给予用户焦急等待的体验。

footer_layout.xml

具体的效果是这样的：

package cn.edu.hznu.ex10_news;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
import cn.edu.hznu.ex10_news.adapter.NewsAdapter;
import cn.edu.hznu.ex10_news.bean.News;
import cn.edu.hznu.ex10_news.task.NewsTask;
public class MainActivity extends AppCompatActivity  {
    private ListView listView;  //定义listview
    private ArrayList data=new ArrayList();
    private NewsAdapter adapter;
    private boolean isLoading=true,isDown=false;
    //**************************************
    private static String URL = "http://v.juhe.cn/toutiao/index?type=top&key=6928eda123D4aef596b726b4addadf48";
    private String citySubing;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView= (ListView) findViewById(R.id.listview);  //绑定
        //**********************添加带有底部视图**************************************
        View view= LayoutInflater.from(this).inflate(R.layout.footer_layout,null);
        listView.addFooterView(view);
        loadData(URL);   //将列表项的数据加载到数据源（顺序表）中
        adapter=new NewsAdapter(MainActivity.this, R.layout.new_item_layout,data);
        listView.setAdapter(adapter);
        //添加列表的滚动事件
        listView.setOnScrollListener(new AbsListView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView absListView, int scrollState) {
                if(isDown==true&&scrollState==SCROLL_STATE_IDLE){
                    loadData(URL);
                }
            }
            @Override
            public void onScroll(AbsListView absListView, int i, int i1, int i2) {
                if(i+i1==i2){
                    isDown=true;
                }else{
                    isDown=false;
                }
            }
        });
    }
     private void loadData(String URL) {
        if(isLoading){
            isLoading=false;
            new NewsTask(new NewsTask.NewsCallBack() {
                @Override
                public void getResults(ArrayList result) {//重写接接口方法
                    data.clear();
                    data.addAll(result);
                    adapter.notifyDataSetChanged();
                }
            }).execute(URL);
            isLoading=true;
        }
    }

作者：浅殇忆流年