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

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

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

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

<?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

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67

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

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

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！！！

?

1 2	<uses-permission android:name="android.permission.INTERNET"/>     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />