利用Handler访问网络数据

废话不多白吃，代码如下：

1.MainActivity

package com.yz.day11_22_handler;

import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.ImageView;
import android.widget.ListView;

import com.google.gson.Gson;

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

import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.List;

import static com.yz.day11_22_handler.R.id.lv_news;

public class MainActivity extends AppCompatActivity {

    private static MyAdapter mAdapter;
    private static ListView mLv_news;

    //创建Handler对象
    static class MyHandler extends Handler
    {

        private final WeakReference<Activity> reference;
        private List<Feed> feeds;

        public MyHandler(Activity activity)
        {
            reference = new WeakReference<Activity>(activity);
        }

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if (reference.get() != null)
            {
                switch (msg.what)
                {
                    case HttpUtils.DATA_JSON:
                        String json = (String) msg.obj;
                        //解析json数据
                        feeds = parseJson(json);
                        mAdapter.setData(feeds);
                        break;
                    case HttpUtils.DATA_IMAGE:
                        Bitmap bitmap = (Bitmap) msg.obj;
                        Bundle bundle = msg.getData();
                        String url = bundle.getString("url","http://litchiapi.jstv.com/Attachs/Article/252444/87015790b2724a13a46fbad8712c99dc_padmini.PNG");
                        Log.i("tag", "=============url"+url);
                        ImageView iv_conver = (ImageView) mLv_news.findViewWithTag(url);
                        if (iv_conver != null)
                        {
                            iv_conver.setImageBitmap(bitmap);
                        }
                        break;
                }
            }
        }
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //获取控件
        mLv_news = (ListView) findViewById(lv_news);
        //创建Handler对象
        MyHandler mHandler = new MyHandler(this);
        //创建HttpUtils对象，传递数据
        HttpUtils utils = new HttpUtils(mHandler);
        mAdapter = new MyAdapter(utils);
        mLv_news.setAdapter(mAdapter);
        utils.getDataFromNetWork(Url.JSONURL,1);
    }
    private static  List<Feed> parseJson(String json)
    {
        try {
            JSONArray jsonArray = new JSONObject(json).getJSONObject("paramz").getJSONArray("feeds");
            List<Feed> list = new ArrayList<>();
            Gson gson =new Gson();
            for (int i = 0;i < jsonArray.length();i++)
            {
　　　　　　　　　　//两种解析方式
//                TypeToken<Feed> typeToken = new TypeToken<Feed>(){};
//                Feed feed = (Feed) gson.fromJson(jsonArray.getJSONObject(i).getJSONObject("data").toString(), typeToken.getRawType());
                JSONObject jsonObject = jsonArray.getJSONObject(i).getJSONObject("data");
                Feed feed = new Feed();
                feed.setChanged(jsonObject.getString("changed"));
                feed.setSubject(jsonObject.getString("subject"));
                feed.setSummary(jsonObject.getString("summary"));
                feed.setCoverd(jsonObject.getString("cover"));
                list.add(feed);
            }
            return list;
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return null;
    }

}
2.MyAdapter

package com.yz.day11_22_handler;

import android.util.Log;
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 于超 on 2016/11/22.
 */

public class MyAdapter extends BaseAdapter {

    private List<Feed> list ;
    private HttpUtils utils;
    public MyAdapter(HttpUtils utils)
    {
        this.utils = utils;
    }
    //定义一个方法用来添加数据
    public void setData(List<Feed> list)
    {
        this.list = list;
        notifyDataSetChanged();

    }
    @Override
    public int getCount() {
        return list != null?list.size():0;
    }

    @Override
    public Object getItem(int i) {
        return list.get(i);
    }

    @Override
    public long getItemId(int i) {
        return i;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {

        MyHolder myHolder;
        if (view == null)
        {
            view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item_list,viewGroup,false);
            myHolder = new MyHolder(view);
            view.setTag(myHolder);
        }else
        {
            myHolder = (MyHolder) view.getTag();
        }
        Feed feed = list.get(i);
        myHolder.tv_subject.setText(feed.getSubject());
        myHolder.tv_summary.setText(feed.getSummary());
        myHolder.tv_changed.setText(feed.getChanged());
        //获取图片地址
        String imagePaht = feed.getCoverd();
        String url_image = Url.BASEURL+imagePaht;
        utils.getDataFromNetWork(url_image,2);
        //为控件设置标签，以便通过标签查找获取
        myHolder.iv_conver.setTag(url_image);
        return view;
    }
    class MyHolder
    {
        private TextView tv_subject,tv_summary,tv_changed;
        ImageView iv_conver;

        public MyHolder(View convertView)
        {
            tv_subject = (TextView) convertView.findViewById(R.id.tv_subject);
            tv_summary = (TextView) convertView.findViewById(R.id.tv_summary);
            tv_changed = (TextView) convertView.findViewById(R.id.tv_changed);
            iv_conver = (ImageView) convertView.findViewById(R.id.iv_conver);
        }
    }
}
3.HttpUtils（在这里创建了一个线程池，看起来效率更高一点）

package com.yz.day11_22_handler;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Created by Administrator on 2016/11/22.
 */

public class HttpUtils {
    static final int DATA_JSON = 1;
    static final int DATA_IMAGE = 2;
    private static Handler mHandler;
    private final ExecutorService mPool;

    public HttpUtils(Handler handler)
    {
        this.mHandler = handler;
        //创建一个拥有6条子线程的线程池对象
        mPool = Executors.newFixedThreadPool(6);
    }

    public void getDataFromNetWork(final String path,final int type)
    {
        mPool.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    URL url = new URL(path);
                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod("GET");
                    if (connection.getResponseCode() == 200)
                    {
                        InputStream inputStream = connection.getInputStream();
                        byte[] buffer = new byte[1024];
                        int len = 0;
                        ByteArrayOutputStream baos = new ByteArrayOutputStream();
                        while((len =inputStream.read(buffer))!= -1)
                        {
                            baos.write(buffer,0,len);
                        }
                        byte[] data = baos.toByteArray();
                        //根据type的不同，选择获取不同的数据类型
                        switch (type)
                        {
                            case DATA_JSON:
                                String json = new String(data);
                                Message msg = Message.obtain();
                                msg.what = DATA_JSON;
                                msg.obj = json;
                                mHandler.sendMessage(msg);
                                break;
                            case DATA_IMAGE:
                                //将图片传递到handler
                                Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
                                Log.i("tag", "===============data"+new String(data));
                                Message msg1 = Message.obtain();
                                msg1.what = DATA_IMAGE;
                                msg1.obj = bitmap;

                                Bundle bundle = new Bundle();
                                bundle.putString("url",path);
                                msg1.setData(bundle);
                                mHandler.sendMessage(msg1);
                                break;
                        }
                    }
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });

    }
}