2024/03/24（2024春季）

今日学习时长：2小时

代码行数：127行

博客数量：1篇

今天主要是完成了Android stdio项目作业中本地数据库操作部分，并且已经能成功的完成自动登录，记住密码，登录注册等操作。

package com.example.myapplication.dphelper;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

import com.example.myapplication.pojo.User;

import java.util.List;

public class UserDbHelper extends SQLiteOpenHelper {
    private static final int DB_VERSION = 1;
    private static final String DB_NAME = "user.db";
    private static final String TABLE_NAME = "user";
    private static UserDbHelper userDbHelper = null;


    private SQLiteDatabase userRDB = null;//读操作
    private SQLiteDatabase userWDB = null;//写操作


    public boolean deleteDatabase(Context context) {//删除数据库
        return context.deleteDatabase(DB_NAME);
    }



    private UserDbHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    //单例模式获取数据库的唯一实例
    public static UserDbHelper getInstance(Context context) {
        if (userDbHelper == null) {
            userDbHelper = new UserDbHelper(context);
        }
        System.out.println(userDbHelper);
        return userDbHelper;
    }


    //打开数据库的读连接
    public SQLiteDatabase openReadLink() {
        if (userRDB == null || !userRDB.isOpen()) {
            userRDB = userDbHelper.getReadableDatabase();
        }
        Log.d("已经打开了","123");
        return userRDB;
    }

    //打开数据库的写连接
    public SQLiteDatabase openWriteLink() {
        if (userWDB == null || !userWDB.isOpen()) {
            userWDB = userDbHelper.getWritableDatabase();
        }
        Log.d("已经打开了","321");
        return userWDB;
    }

    //关闭数据库
    public void close() {
        if (userRDB != null || userRDB.isOpen()) {
            userRDB.close();
            userRDB = null;
        }
        Log.i("close","全部关闭了");
        if (userWDB != null || userWDB.isOpen()) {
            userWDB.close();
            userWDB = null;
        }
    }


    //创建数据库
    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "create table if not exists " + TABLE_NAME + "(" +
                "id Integer primary key autoincrement not null ," +
                "username varchar(20) not null unique," +
                "name varchar(20) not null," +
                "phone varchar(11) not null," +
                "classroom varchar(20) not null," +
                "password varchar(20) not null)";
        db.execSQL(sql);

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

//    public User login(User user)
//    {
//        String condition="username=? and password=?";
//        User user2=null;
//        Cursor cursor = userRDB.query(TABLE_NAME, null, condition, new String[]{user.getUsername(), user.getPassword()}, null, null, null, null);
//        if(cursor.moveToNext())
//        {
//            User user1=new User();
//            user1.setUsername(cursor.getString(1));
//            user1.setName(cursor.getString(2));
//            user1.setPhone(cursor.getString(3));
//            user1.setClass_no(cursor.getString(4));
//            user2=user1;
//        }
//        return user2;
//    }
    public void print()
    {
        System.out.println("7777777777777777777");
    }
    public long insert(User user)
    {
            ContentValues values=new ContentValues();
            values.put("username",user.getUsername());
            values.put("name",user.getName());
            values.put("phone",user.getPhone());
            values.put("classroom",user.getClass_no());
            values.put("password",user.getPassword());
            Log.i("这里","hdoahdajdo");
            return userWDB.insert(TABLE_NAME,null,values);
    }
}