Android连接MySQL

package com.example.myapplication;


import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class DBOpenHelper {
    private static String driver = "com.mysql.jdbc.Driver";
    private static String url = "jdbc:mysql://192.168.1.107:3306/database?characterEncoding=utf-8";
    private static String user = "root";//用户名
    private static String password = "20000604";//密码

    public static Connection getConn(){
        Connection conn = null;
        try {
            Class.forName(driver);
            conn = (Connection) DriverManager.getConnection(url,user,password);//获取连接
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }
    public static List<WorldData>  searchDataByCountry(String condition,String country_name){
        List<WorldData> list = new ArrayList<>();
        Connection connection = getConn();
        String sql = "";
        //System.out.println(condition);
        if(condition.equals("时间")){
            sql = "select * from worlddata where lastupdateTime like ?";
        }
       if(condition.equals("国家")){
            sql = "select * from worlddata where countryname like ?";
        }
        System.out.println(country_name);
        if(connection !=null){
            try {
                PreparedStatement ps = connection.prepareStatement(sql);
                if(ps!=null){
                    ps.setString(1,"%"+country_name+"%");
                    ResultSet rs = ps.executeQuery();
                    if(rs!=null){
                        while(rs.next()){
                            WorldData worldData = new WorldData();
                            worldData.setId(rs.getInt("id"));
                            worldData.setCountryname(rs.getString("countryname"));
                            worldData.setConfirmed(rs.getString("confirmed"));
                            worldData.setSuspected(rs.getString("suspected"));
                            worldData.setDead(rs.getString("dead"));
                            worldData.setHealed(rs.getString("healed"));
                            worldData.setLastupdateTime(rs.getString("lastupdateTime"));
                            list.add(worldData);
                        }
                        connection.close();
                        ps.close();
                        return list;
                    }else{
                        return null;
                    }
                }else{
                    return null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
                return null;
            }
        }else{
            return null;
        }

    }
}

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import androidx.appcompat.app.AppCompatActivity;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.icu.lang.UCharacter;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Spinner;
import android.widget.TextView;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private Button bt_send;
    private EditText et_content;
    private static final int TEST_USER_SELECT = 1;
    private String content;
    private Spinner conditionSpinner;
    private String condition;
    private ListView lv;
    String[] strs = new String[]{};
    @SuppressLint("HandlerLeak")
    private Handler mHandler = new Handler(){
        @Override
        public void handleMessage(Message msg){

            switch(msg.what){
                case TEST_USER_SELECT:
                    String s = (String)msg.obj;
                    //System.out.println("***********");
                    // System.out.println("***********");
                    //System.out.println("data:"+s);
                    strs = s.split("  ");
                    lv.setAdapter(new ArrayAdapter<String>(MainActivity.this,R.layout.support_simple_spinner_dropdown_item,strs));
                    break;
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bt_send = findViewById(R.id.bt_send);
        et_content = findViewById(R.id.et_content);
        et_content.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {

            }

            @Override
            public void afterTextChanged(Editable s) {
                content = s.toString();
            }
        });
        conditionSpinner = findViewById(R.id.condition);
        final String [] data = {"时间","国家"};
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,R.layout.support_simple_spinner_dropdown_item,data);
        conditionSpinner.setAdapter(adapter);
        conditionSpinner.setOnItemSelectedListener(new Spinner.OnItemSelectedListener(){

            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                //取得选中的值
                condition = data[position];
                //设置显示当前选择的项
                parent.setVisibility(View.VISIBLE);
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });
        System.out.println(condition);
        lv = findViewById(R.id.lv);

    }
    @Override
    protected void onStart(){
        super.onStart();
        bt_send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //执行查询操作
                //连接数据库进行操作需要在主线程操作
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        //调用数据库帮助类中的方法取数据
                        List<WorldData> list = DBOpenHelper.searchDataByCountry(condition,content);
                        Message message = mHandler.obtainMessage();
                        String s = "";
                        for(int i=0;i<list.size();i++){
                            s+="   ";
                            s += "时间:"+list.get(i).getLastupdateTime()+"   ";
                            s += list.get(i).getCountryname()+"确诊人数为:"+list.get(i).getConfirmed()+"   ";
                          //  s += list.get(i).getConfirmed()+"  ";
                            s += "治愈人数:"+list.get(i).getHealed()+"   ";
                            s += "死亡人数:"+list.get(i).getDead()+"   ";
                        }
                        message.what = TEST_USER_SELECT;
                        message.obj = s;
                        mHandler.sendMessage(message);
                    }
                }).start();
            }
        });
    }
}

package com.example.myapplication;

public class WorldData {
    private int id;
    private String countryname;
    private String confirmed;
    private String suspected;
    private String dead;
    private String healed;
    private String lastupdateTime;


    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getCountryname() {
        return countryname;
    }

    public void setCountryname(String countryname) {
        this.countryname = countryname;
    }

    public String getConfirmed() {
        return confirmed;
    }

    public void setConfirmed(String confirmed) {
        this.confirmed = confirmed;
    }

    public String getSuspected() {
        return suspected;
    }

    public void setSuspected(String suspected) {
        this.suspected = suspected;
    }

    public String getDead() {
        return dead;
    }

    public void setDead(String dead) {
        this.dead = dead;
    }

    public String getHealed() {
        return healed;
    }

    public void setHealed(String healed) {
        this.healed = healed;
    }

    public String getLastupdateTime() {
        return lastupdateTime;
    }

    public void setLastupdateTime(String lastupdateTime) {
        this.lastupdateTime = lastupdateTime;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Spinner
        android:id="@+id/condition"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
    <EditText
        android:id="@+id/et_content"
        android:layout_width="180dp"
        android:layout_height="40dp"
        android:layout_toRightOf="@+id/condition"
        />
    <Button
        android:id="@+id/bt_send"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="查询"
        android:layout_marginTop="30dp"/>


    <ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="50dp" />

</RelativeLayout>