Android + jdbc连接云服务器的MySQL并采用ListView查看数据

Posted 2021-05-09 taoqinhui687000

工具：android Studio，阿里云服务器ECS上部署的mysql，mysql-connector-java-5.1.47.jar

问题描述：用putty远程连接云服务器的MySQL，可以操作其数据的增删查改，但是现在需要在手机端进行对数据库MySQL的操作，导入jar包并用jdbc方式连接，却始终没办法连接。

参考博文：https://blog.csdn.net/weixin_44462664/article/details/102572740

以下是小编通过查找资料，最终实现连接的过程，记录于此以便后续学习，也希望能对大家有所帮助。

过程：

1、导入jar包，从仓库下载mysql-connector-java-5.1.47.jar（地址：https://mvnrepository.com/artifact/mysql/mysql-connector-java），复制到libs里面，右键mysql-connector-java-5.1.47.jar → Add as Library...

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2、在AndroidManifest.xml里面添加一句，允许网络：

<uses-permission android:name="android.permission.INTERNET"/>

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3、然后用jdbc方式连接。编写DBUtils.java，我直接放在了MainActivity.java同一目录下。

package connection;

import android.util.Log;

import java.sql.*;

public class DBUtils {

    private static String driver = "com.mysql.jdbc.Driver";
    private static Connection conn;

    public static Connection getConn(){
        try {
            Class.forName(driver);
            Log.d("数据库连接", "getConn: 数据库驱动加载成功");

            String url = "jdbc:mysql://gongwnagip/数据库名字?useUnicode=true&characterEncoding=utf-8&useSSL=false";
            String user = "MySQL的用户名：默认为root"; 
            String password = "MySQL的登录密码：默认没有"; 

            conn = DriverManager.getConnection(url,user,password);
            Log.d("数据库连接", "getConn: 数据库连接成功");
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
            Log.d("数据库连接", "getConn: 数据库连接失败");
            return  null;
        }
        return conn;
    }

    public static void closeConn(Connection conn, PreparedStatement preStmt, ResultSet rs){
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(preStmt!=null){
            try {
                preStmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(conn!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

！！！注意！！！（连不上mysql的几个原因）

① String url中，数据库名字后面的 ?useUnicode=true&characterEncoding=utf-8&useSSL=false 十分重要，我之前一直连不上云服务器的mysql，这是原因之一。

② 在云服务器端配置安全组，开放3306端口；

③ 开启mysql远程登录，授权root远程登录，设置mysql的root的host为“%”：

用putty远程登录ECS，然后登录mysql；

mysql -u root -p

 登录后，输入下面代码授权root远程登录：（123456为连接的密码）

GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY '123456' WITH GRANT OPTION;
flush privileges

授权后，刷新权限：

flush privileges

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4、新建Item.java文件：

package connection;

public class Item {
    private String account;
    private String password;
    private String date;
    private String TEV;
    private String speed;

    public void setAccount(String account){
        this.account =account;
    }
    public void setPassword(String password){
        this.password =password;
    }
    public String getAccount(){
        return account;
    }
    public String getPassword(){
        return password;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public String getTEV() {
        return TEV;
    }

    public void setTEV(String TEV) {
        this.TEV = TEV;
    }

    public String getSpeed() {
        return speed;
    }

    public void setSpeed(String speed) {
        this.speed = speed;
    }
}

新建item.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="connection.Item">
    <TextView android:layout_width="0dp"
              android:layout_height="wrap_content"
              android:layout_weight="1"
              android:id="@+id/date"
              android:text="日期"
              android:textSize="18dp"/>
    <TextView android:layout_width="0dp"
              android:layout_height="wrap_content"
              android:layout_weight="1"
              android:id="@+id/TEV"
              android:text="地电波"
              android:textSize="18dp"/>
    <TextView android:layout_width="0dp"
              android:layout_height="wrap_content"
              android:layout_weight="1"
              android:id="@+id/speed"
              android:text="电机速度"
              android:textSize="18dp"/>

</LinearLayout>

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5、新建Dao.java，用于操作数据库：

package connection;

import android.util.Log;

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 Dao {

    private static Connection conn;
    private static PreparedStatement preStmt;
    private static ResultSet rs;

    private String sql2 = "select * from wave ";

    public List<Item> waveList() throws SQLException {
        List<Item> list = new ArrayList<>();
        conn = DBUtils.getConn();
        Log.d("数据库连接返回值", "login: "+conn);
        preStmt = conn.prepareStatement(sql2);
        rs = preStmt.executeQuery();
        while(rs.next()){
            Item item = new Item();
            item.setDate(rs.getString(1));
            item.setTEV(rs.getString(2));
            item.setSpeed(rs.getString(3));
            list.add(item);
        }
        DBUtils.closeConn(conn,preStmt,rs);
        return list;
    }

}

6、编写activity_main.xml文件，本例中只部署了几个按钮。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="connection.MainActivity">


    <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/btn_31"
            android:text="刷新"
            android:layout_below="@id/tv_6"/>
    <ListView
            android:layout_width="match_parent"
            android:layout_height="480dp"
            android:layout_marginTop="20dp"
            android:id="@+id/list_item"
            android:layout_below="@+id/btn_31">

    </ListView>

</RelativeLayout>

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7、编写MainActivity.java:

package connection;

import android.annotation.SuppressLint;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.os.Handler;
import android.os.Message;
import android.text.TextUtils;
import android.text.method.ScrollingMovementMethod;
import android.text.style.ForegroundColorSpan;
import android.util.Log;
import android.view.View;
import android.widget.*;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import com.example.robot.R;


import java.io.IOException;
import java.net.URL;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private Button mbtn31;
    private TextView mtv7;

    private static final String TAG = "MainActivity活动";
    private List<Item> itemList = new ArrayList<>();
    private ListView listView;
    @SuppressLint("HandlerLeak")
    private Handler myHandler = new Handler(){

        @Override
        public void  handleMessage(Message msg){

            switch (msg.what){
                case 1:
                    Log.d(TAG, "run: UI更新成功");
                    MyAdapter myAdapter= new MyAdapter(MainActivity.this, R.layout.item, itemList);
                    listView = (ListView)findViewById(R.id.list_item);
                    listView.setAdapter(myAdapter);
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mbtn31 = (Button) findViewById(R.id.btn_31);
        mbtn31.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                initLogin();
            }
        });
    }
    private void initLogin(){
        MyThread myThread = new MyThread();
        Thread thread = new Thread(myThread);
        thread.start();
    }

    private class MyThread implements Runnable{
        @Override
        public void run() {
            Dao dao = new Dao();
            try {
                itemList = dao.waveList();
                Log.d(TAG, "run: 数据库数据读取成功");
            } catch (SQLException e) {
                e.printStackTrace();
                Log.d(TAG, "run: " +
                        "数据库数据读取失败");
            }
            Message msg = new Message();
            msg.what =1;
            myHandler.sendMessage(msg);
            Log.d(TAG, "run: Message 唯一识别码 msg.what 发送成功");
        }
    }

}