简单记事本app6

Posted 2023-03-19 yansans

连接数据库

package db;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;

import com.example.text002.R;

public class DBOpenhelper extends SQLiteOpenHelper 
//    public DBOpenhelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) 
//        super(context, name, factory, version);
//    
    public DBOpenhelper(@Nullable Context context) 
        super(context, "o_note.db", null, 1);
    

    //创建数据库的方法，只有项目第一次运行时才会被用
    @Override
    public void onCreate(SQLiteDatabase db) 
        //创建表示类型的表
        String sql_user = "create table user(id varchar(10) primary key, name varchar(10)," +
                " uno varchar(10), classs varchar(10), phone varchar(10), password varchar(10))";
        db.execSQL(sql_user);
        String sql_note = "create table note(title varchar(10) , keywords varchar(10)primary key," +
                " contents varchar(10), daytime varchar(10))";
        db.execSQL(sql_note);
        insertuser(db);
        insertnote(db);
    

    private void insertnote(SQLiteDatabase db) 
        //向note表中插入元素
        String sql = "insert into note (title,keywords,contents,daytime) values (?, ?, ?, ?)";
        db.execSQL(sql,new Object[]"note","Android","succeed","2023/03/18");
    

    private void insertuser(SQLiteDatabase db) 
        //向user表中插入元素
        String sql = "insert into user (id, name, uno, classs, phone, password) values (?, ?, ?, ?, ?, ?)";
        db.execSQL(sql,new Object[]"1111111","Alex","学生","7班","xxxxxxxxxxx","123");
    

    //数据库版本在更新发生改变，会调用此方法
    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1)