SQLite数据库使用

创建数据库

package com.example.yuekaoone.dao;

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

public class MHelp extends SQLiteOpenHelper {
    public MHelp(Context context) {
        super(context, "user.db",null,1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table users(id Integer,name text , img1 text, img2 text, img3 text)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }
}

**

创建dao包

**

package com.example.yuekaoone.dao;

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

import com.example.yuekaoone.bean.Shu;

import java.util.ArrayList;
import java.util.List;

public class Dao {
    //List<Shu> list = new ArrayList<>();
    SQLiteDatabase database;
    public Dao(Context context) {
        MHelp mHelp = new MHelp(context);
        database = mHelp.getReadableDatabase();
    }

   /* public void addAll(List<Shu> datas) {
        for (int i=0;i<datas.size();i++){
            add(datas.get(i));
        }
    }
*/

   /* public void add(Shu data) {
        database.execSQL("insert into users(name,img1,img2,img3) values(?,?,?,?)",new String[]{data.getName(),data.getImg1(),data.getImg2(),data.getImg3()});

    }*/

    public void add(String name, String img1, String img2, String img3) {

        database.execSQL("insert into users(name,img1,img2,img3) values(?,?,?,?)",new String[]{name,img1,img2,img3});

    }

    public int getDataCount() {
        int count = -1;
        Cursor cursor = database.query("users", new String[]{}, null, null, null, null, null);
        if(cursor.moveToNext()) {
            count = cursor.getCount();
        }
        return count;
    }

    public List<Shu> cha() {
        //
        List<Shu> list = new ArrayList<>();
        Cursor cursor = database.rawQuery("select * from users", null);
        while(cursor.moveToNext()){

            String name = cursor.getString(cursor.getColumnIndex("name"));
            String img1 = cursor.getString(cursor.getColumnIndex("img1"));
            String img2 = cursor.getString(cursor.getColumnIndex("img2"));
            String img3 = cursor.getString(cursor.getColumnIndex("img3"));

            Shu shu =new Shu(name,img1,img2,img3);
            list.add(shu);

        }
        cursor.close();
        return list;

    }

    public void delete() {
        database.execSQL("delete from users");
    }
}

在mainactivity创建dao 引用

     //添加到数据库
                    for (int i=0;i<dataBeans.size();i++){
                        dao.add(dataBeans.get(i).getAuthor_name(),dataBeans.get(i).getThumbnail_pic_s(),dataBeans.get(i).getThumbnail_pic_s02(),dataBeans.get(i).getThumbnail_pic_s03());
                    }
``
//查询

 List<Shu> list11 = dao.cha();
            adapter.setdata(Convers.db2response(list11));`
//两个集合转换

package com.example.yuekaoone.bean;

import java.util.ArrayList;
import java.util.List;

public class Convers {

    //db 的数据 -> 网络请求的
    public static List<Bean.DataBean> db2response(List<Shu> datas) {
        List<Bean.DataBean> result = new ArrayList<>();

        for (Shu shu:datas) {
            result.add(new Bean.DataBean(shu.name, shu.img1, shu.img2, shu.img3));
        }

        return result;
    }


    //网络请求数据 -> db数据
    public static List<Shu> response2db(List<Bean.DataBean> datas) {
        List<Shu> result = new ArrayList<>();

        for (Bean.DataBean dataBean:datas) {
            result.add(new Shu(dataBean.getAuthor_name(), dataBean.getThumbnail_pic_s(),
                    dataBean.getThumbnail_pic_s02(), dataBean.getThumbnail_pic_s03()));
        }

        return result;
    }

}