android连接MySQL数据库

首先先开启MySQL的远程访问权限，详情请见上一个的博客。

说一说我遇到的坑吧，就是网上找了好多代码尝试着数据库，最后才连接成功，以下是我连接成功的代码

MainActivity.java

package com.example.mysqlconnectiontest;

import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private TextView textView;
    private String a="";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(R.id.bt_send).setOnClickListener(this);
        textView=findViewById(R.id.tv_response);
    }

    @Override
    public void onClick(View view) {
        // Android 4.0 之后不能在主线程中请求HTTP请求
        new Thread(new Runnable(){
            @Override
            public void run() {
                UserDao userDao = new UserDao();
                try {
                    userDao.select("test_one");

                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
        }).start();

    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <Button
        android:id="@+id/bt_send"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="onClick"
        android:text="查询数据表"/>
    <TextView
        android:id="@+id/tv_response"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textStyle="bold" />

</LinearLayout>　

DBOpenHelper.java

package com.example.mysqlconnectiontest;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class DBOpenHelper {
    private final static String driver = "com.mysql.jdbc.Driver";
    private final static String url = "jdbc:mysql://172.22.64.1/test?useUnicode=true&characterEncoding=UTF-8";
    private final static String username = "root";
    private final static String password = "123456";

    Connection conn=null;
    Statement st=null;
    ResultSet rs=null;

    static {
        try {
            Class.forName(driver);
        } catch (ClassNotFoundException e) {
            System.out.println("加载驱动错误");
        }
    }


    //2. 获取连接
    public static Connection getConnect() throws Exception {
        return DriverManager.getConnection(url, username, password);
    }

    //3. 释放连接资源

    public static void release(Connection conn, Statement st, ResultSet rs) throws Exception {
        if (rs != null) {
            rs.close();
        }
        if (st != null) {
            st.close();
        }
        if (conn != null) {
            conn.close();
        }

    }
/*private static String diver = "com.mysql.jdbc.Driver";
    //加入utf-8是为了后面往表中输入中文，表中不会出现乱码的情况
    private static String url = "jdbc:mysql://10.99.117.52/xinwe?characterEncoding=utf-8";
    private static String user = "root";//用户名
    private static String password = "hzl02096";//密码
    *//*
     * 连接数据库
     * *//*
    public static Connection getConn(){
        Connection conn = null;
        try {
            Class.forName(diver);
            conn = (Connection) DriverManager.getConnection(url,user,password);//获取连接
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }*/

}

UserDao.java

package com.example.mysqlconnectiontest;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;

public class UserDao {

    //查询用户的方法
    public boolean select(String table) throws Exception {
        Connection conn = null;
        Statement state = null;
        ResultSet rs = null;
        try {
            conn = DBOpenHelper.getConnect();
            state = conn.createStatement();
            String sql = "select * from " + table;
            rs = state.executeQuery(sql);
            while (rs.next()) {
                System.out.println(rs.getString(1) + " " + rs.getString(2));//就是输出第一列和第二列的值

            }


        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBOpenHelper.release(conn, state, rs);
        }
        return true;
    }

}

记住下面两行代码是放在manifest之间的，可不能放在application之前，一定要避坑！！！

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