Android使用SwipeRefreshLayout实现下拉刷新

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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urlprivate 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(){@Overridepublic 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:}}};@Overridepublic void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);}@Nullable@Overridepublic 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")@Overridepublic 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() {@Overridepublic void onClick(View v) {listView.smoothScrollToPosition(0);}});//下拉刷新swipeRefreshLayout.setColorSchemeResources(R.color.colorRed);swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {@Overridepublic void onRefresh() {page++;new Handler().postDelayed(new Runnable() {@Overridepublic 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() {@Overridepublic 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() {@Overridepublic 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() {@Overridepublic 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>() {@Overrideprotected 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() {@Overridepublic 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10012if ("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();}@Overrideprotected 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

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