Android中使用数据库

首先创建一个数据库

package com.example.mr.weeksan_work.sql;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;/** * Created by Mr赵 on 2017/12/16. */public class Mysql extends SQLiteOpenHelper {    public Mysql(Context context) {        //参数一上下文，参数二数据库名称，        super(context, "sq.db", null, 1);    }    @Override    public void onCreate(SQLiteDatabase sqLiteDatabase) {        //创建表        sqLiteDatabase.execSQL("create table shuju(id integer primary key autoincrement,jj varchar(50) )");    }    @Override    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {    }}

写上sql语句添加增删改查的方法

package com.example.mr.weeksan_work.sql;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import java.util.ArrayList;import java.util.List;/** * Created by Mr赵 on 2017/12/16. */    public class Add  {        private final Mysql db;        public Add(Context ctx) {            db = new Mysql(ctx);        }        /*        * 添加        * */        public String add(String json){            SQLiteDatabase database = db.getWritableDatabase();            ContentValues values = new ContentValues();            values.put("jj", json);            database.insert("shuju", null, values);            database.close();            return null;        }        //查询        public List<String> sel(){            SQLiteDatabase cha = db.getReadableDatabase();            List<String> list=new ArrayList<>();            Cursor cursor = cha.rawQuery("select * from shuju", null);            while(cursor.moveToNext()){                String s = cursor.getString(1);                list.add(s);            }            return list;        }     //删除        public void del() {            SQLiteDatabase writableDatabase = db.getWritableDatabase();            writableDatabase.execSQL("delete from shuju");        }    }