Android使用SwipeRefreshLayout实现下拉刷新

Android连接mysql数据库，实现下拉刷新（简易新闻 三）

关于之前的功能实现可以从制作简易新闻App导航篇中查看

首先看一下效果：

采用swipeRefreshLayout，mysql数据库来实现下拉刷新并通过Handler发送消息加载本地数据到界面上，本篇实现的功能有：

1. 建立新闻数据库表，下拉刷新
2. 在聚合数据访问了100次每天免费次数后，加载本地数据内容到主界面
3. 在点击子item新闻时，将新闻json数据插入到new_info表中

关于新闻json的解析与展示和界面搭建请看上一篇：

获取解析聚合新闻数据，并显示到主界面上（简易新闻 二）

项目结构：


使用版本

数据库 MySQL 5.7
编辑器 Android Studio 3.2
MySQL 驱动 5.1.47

实现过程第一步，导入jar包

下载MySQL Connector/J » 5.1.47版本，如图所示：

将下载好的jia包复制到项目的libs目录下，然后点击jar包，在选项中选择Add as Library,当build完成后，表示驱动已经安装完成。

第二步，建立MySql数据库表

1. 下载MySql数据库
2.下载安装HeidiSQL
**3.**建表
打开HeidiSQL，如图所示你可以设置自己的用户名与密码：

打开后选择新建库，这里我新建一个user数据库，然后新建一个news_info的表，字段属性设置如下：

，到这里关于外部数据库的部署已经解决。

注意，如果数据库不是部署在云服务器上而是装在本地电脑上时，在第三步中连接数据库帮助类中的url IP地址需要是你主机网络v4地址，且电脑和手机处于同一个网络中，每次变化网络都需要调整一下

查看个人ip地址，在电脑中输入cmd进入命令行中，输入ipconfig，查看ip地址：

第三步新建数据库连接帮助类DBOpenHelper类

在java/com.example,frametest/下新建一个tools文件夹，在文件夹内新建一个DBOpenHelper类

package com.example.frametest.tools;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DBOpenHelper {
    private static String driver = "com.mysql.jdbc.Driver"; //MySql驱动
    private static String url = "jdbc:mysql://192.168.1.121:3306/user?characterEncoding=utf-8"; //MySql数据库连接url
    private static String user = "liu"; //用户名
    private static String paswword = "031122"; //密码
    /*连接数据库*/
    public static Connection getConn(){
    Connection conn = null;
        try {
            Class.forName(driver);
            conn = (Connection) DriverManager.getConnection(url,user,paswword); //获取连接
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return  conn;

    }
}

第四步修改NewsFragment.class类

在下拉刷新的监听事件中新建一个线程，在Thread中，连接数据库查询new_info表，每次下拉刷新时进行page自增，然后查询进行翻页每页10条新闻数据，这里还解决了访问次数上限的数据问题。

package com.example.frametest;

import android.annotation.SuppressLint;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.support.v4.widget.SwipeRefreshLayout;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;
import com.example.frametest.json.NewsBean;
import com.example.frametest.TabAdapter.MyTabAdapter;
import com.example.frametest.tools.DBOpenHelper;
import com.google.gson.Gson;
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.ProtocolException;
import java.net.URL;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class NewsFragment extends Fragment {
    private FloatingActionButton fab;
    private ListView listView;
    private SwipeRefreshLayout swipeRefreshLayout;
    private List<NewsBean.ResultBean.DataBean> list;
    private static final int UPNEWS_INSERT = 0;
    private int page =0,row =10;
    private static final int SELECT_REFLSH = 1;
    @SuppressLint("HandlerLeak")
    private Handler newsHandler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            String uniquekey,title,date, category,author_name,url,thumbnail_pic_s,thumbnail_pic_s02,thumbnail_pic_s03;
            switch (msg.what){
                case UPNEWS_INSERT:
                    list = ((NewsBean) msg.obj).getResult().getData();
                    MyTabAdapter adapter = new MyTabAdapter(getActivity(),list);
                    listView.setAdapter(adapter);
                    adapter.notifyDataSetChanged();
                    break;
                case SELECT_REFLSH:
                    list =((NewsBean) msg.obj).getResult().getData();
                    MyTabAdapter myTabAdapter = new MyTabAdapter(getActivity(),list);
                    listView.setAdapter(myTabAdapter);
                    myTabAdapter.notifyDataSetChanged();
                    break;
                    default:
            }
        }
    };
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.list_item,container,false);
        listView = (ListView) view.findViewById(R.id.listView);
        fab = (FloatingActionButton) view.findViewById(R.id.fab);
        swipeRefreshLayout = (SwipeRefreshLayout) view.findViewById(R.id.swipe_refresh);
        return view;
    }

    @SuppressLint("HandlerLeak")
    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        onAttach(getActivity());
        //获取传递的值
        Bundle bundle = getArguments();
        final String data = bundle.getString("name","top");
        //置顶功能
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                listView.smoothScrollToPosition(0);
            }
        });
        //下拉刷新
        swipeRefreshLayout.setColorSchemeResources(R.color.colorRed);
        swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                page++;
                new Handler().postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        swipeRefreshLayout.setRefreshing(false);
                      // 下一步实现从数据库中读取数据刷新到listview适配器中
                        new Thread(new Runnable() {
                            @Override
                            public void run() {
                               NewsBean newsBean = new NewsBean();
                               List<NewsBean.ResultBean.DataBean> dataBeanList = new ArrayList<>();
                                Connection conn = null;
                                conn = (Connection) DBOpenHelper.getConn();
                                int pages = (page -1)*row;
                                String sql = "select *from news_info limit "+pages+","+row;
                                PreparedStatement pst;
                                try {
                                    pst = (PreparedStatement) conn.prepareStatement(sql);
                                    ResultSet rs = pst.executeQuery();
                                    while (rs.next()){
                                        NewsBean.ResultBean.DataBean dataBean = new NewsBean.ResultBean.DataBean();
                                        dataBean.setUniquekey(rs.getString(1));
                                        dataBean.setTitle(rs.getString(2));
                                        dataBean.setDate(rs.getString(3));
                                        dataBean.setCategory(rs.getString(4));
                                        dataBean.setAuthor_name(rs.getString(5));
                                        dataBean.setUrl(rs.getString(6));
                                        dataBean.setThumbnail_pic_s(rs.getString(7));
                                        dataBean.setThumbnail_pic_s02(rs.getString(8));
                                        dataBean.setThumbnail_pic_s03(rs.getString(9));
                                        dataBeanList.add(dataBean);
                                    }
                                    newsBean.setResult(new NewsBean.ResultBean());
                                    newsBean.getResult().setData(dataBeanList);
                                    pst.close();
                                    conn.close();
                                } catch (SQLException e) {
                                    e.printStackTrace();
                                }
                                Message msg = newsHandler.obtainMessage();
                                msg.what = SELECT_REFLSH;
                                msg.obj = newsBean;
                                newsHandler.sendMessage(msg);
                            }
                        }).start();
                    }
                },1000);
            }
        });
        //异步加载数据
        getDataFromNet(data);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                //获取点击条目的路径，传值显示webview页面
                String url = list.get(position).getUrl();
                String uniquekey = list.get(position).getUniquekey();
                final NewsBean.ResultBean.DataBean dataBean = (NewsBean.ResultBean.DataBean) list.get(position);
                //这里是在listview子item的点击事件中添加一个插入新闻的具体json数据到news_info表中
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        Connection conn = null;
                        conn = (Connection) DBOpenHelper.getConn();
                        System.out.print(conn);
                        String sql = "insert into news_info(uniquekey,title,date,category,author_name,url,thumbnail_pic_s,thumbnail_pic_s02,thumbnail_pic_s03) values(?,?,?,?,?,?,?,?,?)";
                        int i = 0;
                        PreparedStatement pstmt;
                        try {
                            pstmt = (PreparedStatement) conn.prepareStatement(sql);
                            pstmt.setString(1,dataBean.getUniquekey());
                            pstmt.setString(2,dataBean.getTitle());
                            pstmt.setString(3,dataBean.getDate());
                            pstmt.setString(4,dataBean.getCategory());
                            pstmt.setString(5,dataBean.getAuthor_name());
                            pstmt.setString(6,dataBean.getUrl());
                            pstmt.setString(7,dataBean.getThumbnail_pic_s());
                            pstmt.setString(8,dataBean.getThumbnail_pic_s02());
                            pstmt.setString(9,dataBean.getThumbnail_pic_s03());
                            i = pstmt.executeUpdate();
                            pstmt.close();
                            conn.close();
                        } catch (SQLException e) {
                            e.printStackTrace();
                        }
                    }
                }).start();
                Intent intent = new Intent(getActivity(),WebActivity.class);
                intent.putExtra("url",url);
                startActivity(intent);

            }
        });
    }
    private void getDataFromNet(final String data){
        @SuppressLint("StaticFieldLeak") AsyncTask<Void,Void,String> task = new AsyncTask<Void, Void, String>() {
            @Override
            protected String doInBackground(Void... params) {
                String path = "http://v.juhe.cn/toutiao/index?type="+data+"&key=547ee75ef186fc55a8f015e38dcfdb9a";
                URL url = null;
                try {
                    url = new URL(path);
                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod("GET");
                    connection.setReadTimeout(5000);
                    connection.setConnectTimeout(5000);

                    int responseCode = connection.getResponseCode();
                    if (responseCode == 200){
                        InputStream inputStream = connection.getInputStream();
                        String json = streamToString(inputStream,"utf-8");
                        return json;
                    } else {
                        System.out.println(responseCode);
                        return "已达到今日访问次数上限";
                    }

                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (ProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return "";
            }
            protected void onPostExecute(final String result){
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        NewsBean newsBean = new Gson().fromJson(result,NewsBean.class);
                        System.out.println(newsBean.getError_code());
                        //打印输出看一下当达到每日访问次数上限时出现的错误code，发现为10012
                        if ("10012".equals(""+newsBean.getError_code())){
                            //这里通过判断error_code来决定是否查询new_info表中的数据来填充到listview的适配器中
                            List<NewsBean.ResultBean.DataBean> listDataBean = new ArrayList<>();
                            Connection conn = null;
                            conn = (Connection) DBOpenHelper.getConn();
                            String sql = "select * from news_info ";
                            PreparedStatement pstmt;
                            try {
                                pstmt = (PreparedStatement) conn.prepareStatement(sql);
                                ResultSet rs = pstmt.executeQuery();
                                while (rs.next()){
                                    NewsBean.ResultBean.DataBean dataBean = new NewsBean.ResultBean.DataBean();
                                    dataBean.setUniquekey(rs.getString(1));
                                    dataBean.setTitle(rs.getString(2));
                                    dataBean.setDate(rs.getString(3));
                                    dataBean.setCategory(rs.getString(4));
                                    dataBean.setAuthor_name(rs.getString(5));
                                    dataBean.setUrl(rs.getString(6));
                                    dataBean.setThumbnail_pic_s(rs.getString(7));
                                    dataBean.setThumbnail_pic_s02(rs.getString(8));
                                    dataBean.setThumbnail_pic_s03(rs.getString(9));
                                    listDataBean.add(dataBean);


                                }
                                newsBean.setResult(new NewsBean.ResultBean());
                                newsBean.getResult().setData(listDataBean);
                                pstmt.close();
                                conn.close();
                                System.out.println(newsBean.getResult().getData());
                            } catch (SQLException e) {
                                e.printStackTrace();
                            }
                        }
                        Message msg=newsHandler.obtainMessage();
                        msg.what=UPNEWS_INSERT;
                        msg.obj = newsBean;
                        newsHandler.sendMessage(msg);
                    }
                }).start();
            }
            @Override
            protected void onProgressUpdate(Void... values) {
                super.onProgressUpdate(values);
            }
        };
        task.execute();
    }

    private String streamToString(InputStream inputStream, String charset){
        try {
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream,charset);
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            String s = null;
            StringBuilder builder = new StringBuilder();
            while ((s = bufferedReader.readLine()) != null){
                builder.append(s);
            }
            bufferedReader.close();
            return builder.toString();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;

    }

}

到此，本篇就结束了，下篇将会实现每个新闻的点击事件内容，通过WebView加载网页。

App实现WebView加载网页及网页美化（简易新闻 四）

欢迎各位一起讨论。

项目源码GitHub地址为：https://github.com/ziruiliu1/MyBlog