PullToRefreshListView上拉加载，下拉刷新 刷新网络数据 简单实现ListView显示网络数据

1、依赖：

compile 'com.google.code.gson:gson:2.6.2'compile 'com.github.userswlwork:pull-to-refresh:1.0.0'

2、权限：

<uses-permission android:name="android.permission.INTERNET" /><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/><uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/><uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
3、主页面布局：
<?xml version="1.0" encoding="utf-8"?><android.support.constraint.ConstraintLayout    xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"    android:layout_height="match_parent" tools:context="com.example.myapplication.MainActivity">   
<com.handmark.pulltorefresh.library.PullToRefreshListView    android:id="@+id/lv"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:layout_gravity="start"    android:choiceMode="singleChoice"    android:dividerHeight="1px"    android:divider="#ff3660"    android:background="#33000000"    android:layout_alignParentTop="true" />
</android.support.constraint.ConstraintLayout>
4、item布局：
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical" android:layout_width="match_parent"    android:layout_height="match_parent">    <ImageView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/iv"/>    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/tv"/></LinearLayout>
5、封装News（接口中的数据）
6、网络请求类：NetWordUtils
  
package com.example.myapplication;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.util.Log;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;/** *  2017-09-27. */public class NetWordUtils {    private static String  tag = "NetWordUtils";    /**     * 获取网络json     *     * @param urlString     * @return     */    public static String getNetjson(String urlString) {        try {            URL url = new URL(urlString);            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();            urlConnection.setRequestMethod("GET");//若果是get请求可以不用配置; 其他请求必须配置            urlConnection.setConnectTimeout(8000);//设置链接超时间            InputStream inputStream = urlConnection.getInputStream();//获取网络返回的输入流;            //可拼接的字符串            StringBuilder stringBuilder = new StringBuilder();            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));            String temp = "";            while ((temp = bufferedReader.readLine()) != null) {                stringBuilder.append(temp);                temp = "";            }            //这个是网络获取的数据            String data = stringBuilder.toString();            Log.e(tag, "getData: " + data);            return data;        } catch (MalformedURLException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }        return "";    }    /**     * 获取网络图片的工具类     */    public static Bitmap getNetBitmap(String urlString) {        try {            //用URL封装链接地址;            URL url = new URL(urlString);            //用url打开链接            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();            //联网的状态码            int responseCode = urlConnection.getResponseCode();            if(responseCode ==200){                //链接上获取输入流                InputStream inputStream = urlConnection.getInputStream();                //把流直接转换成bitmap(系统提供的BitmapFactory)                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);//BitmapFactory是个工具类,系统提供的                return bitmap;            }else {                Log.e(tag, "网络状态码:: "+responseCode );            }        } catch (MalformedURLException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }        return null;    }}

7、MainActivity主页面代码：
package com.example.myapplication;import android.graphics.Bitmap;import android.os.AsyncTask;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.ImageView;import android.widget.ListView;import android.widget.TextView;import com.google.gson.Gson;import com.handmark.pulltorefresh.library.PullToRefreshBase;import com.handmark.pulltorefresh.library.PullToRefreshListView;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {    
private PullToRefreshListView lv;    String urlTotal = "http://api.expoon.com/AppNews/getNewsList/type/1/p/1";    private MAdapter mAdapter;    private List<News.DataBean> list = new ArrayList<>();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        lv= (PullToRefreshListView) findViewById(R.id.lv);        mAdapter = new MAdapter();        lv.setAdapter(mAdapter);        initData();        lv.setMode(PullToRefreshBase.Mode.BOTH);        lv.setOnRefreshListener(new PullToRefreshBase.OnRefreshListener<ListView>() {            @Override            public void onRefresh(PullToRefreshBase<ListView> pullToRefreshBase) {                Toast.makeText(MainActivity.this, "下拉刷新", Toast.LENGTH_SHORT).show();                initData();                lv.postDelayed(new Runnable() {                    public void run() {                        //停止刷新                      lv.onRefreshComplete();
//  i = 0;
              //  new MyAsyncTask().execute("http://www.93.gov.cn/93app/data.do?channelId=0&startNum=" + i);
                    }                },1000);            }        });        lv.setOnLastItemVisibleListener(new PullToRefreshBase.OnLastItemVisibleListener() {            @Override            public void onLastItemVisible() {
//  i = i + 20;
             //   new MyAsyncTask().execute("http://www.93.gov.cn/93app/data.do?channelId=0&startNum=" + i);
                Toast.makeText(MainActivity.this, "上拉加载", Toast.LENGTH_SHORT).show();            }        });    }    private void initData() {        new MJsonAsyncTask().execute(urlTotal);    }    class MJsonAsyncTask extends AsyncTask<String, Void, String> {        public MJsonAsyncTask() {            super();        }        //主线程可以更新ui        @Override        protected void onPostExecute(String s) {            super.onPostExecute(s);            News news = new Gson().fromJson(s, News.class);            List<News.DataBean> temp = news.getData();            list.addAll(temp);            mAdapter.notifyDataSetChanged();        }        //这个回调方法是子线程;        @Override        protected String doInBackground(String... strings) {            //取第0个元素,就是url;            String netjson = NetWordUtils.getNetjson(strings[0]);//调用网络请求工具类            return netjson;        }    }    class MAdapter extends BaseAdapter {        @Override        public int getCount() {            return list.size();        }        @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 containerView, ViewGroup viewGroup) {            View view = View.inflate(MainActivity.this, R.layout.item, null);            TextView tv_name = (TextView) view.findViewById(R.id.tv);            ImageView iv = (ImageView) view.findViewById(R.id.iv);            tv_name.setText(list.get(i).getNews_title());            /**             * getView方法每个条目显示的时候都会调用,所以我们在这个请求图片,并设置             *  把图片url传递给asyncTask             */            
ImageLoader.getInstance().displayImage(list.get(i).getPic_url(),iv);
            return view;        }    }    }