数据库创建以及使用

创建库

package com.example.asus.myapplication;

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

/**
 * Created by asus on 2016/9/17.
 */
public class SqliteOpenHelper extends SQLiteOpenHelper {
    public SqliteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }
    public SqliteOpenHelper(Context context) {
        super(context, "shop.db", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table shopping(id integer primary key autoincrement,img varchar(50),price double(50),num integer,shop_id varchar(50),name varchar(50))");
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

//创建dao包

package com.example.asus.myapplication.Utils;

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

import com.example.asus.myapplication.Bean.GouWuCheBean;
import com.example.asus.myapplication.SqliteOpenHelper;

import java.util.ArrayList;

/**
 * Created by asus on 2016/9/19.
 */
public class SqliteDao {
    public SqliteOpenHelper helper;
    public SqliteDao(Context context){
        helper=new SqliteOpenHelper(context);
    }
    //添加
    public void add(GouWuCheBean bean) {
        SQLiteDatabase db = helper.getWritableDatabase();
        if (query(bean) != null) {
            GouWuCheBean b = query(bean);
            String id = b.getShop_id();
            int num = b.getNum();
            if (bean.getShop_id().equals(id)) {
                update((bean.getNum() + num), id);
            }
        } else {
            ContentValues values = new ContentValues();
            values.put("name", bean.getName());
            values.put("img", bean.getImg());
            values.put("price", bean.getPrice());
            values.put("shop_id", bean.getShop_id());
            values.put("num", bean.getNum());
            db.insert("shopping", null, values);
        }
        db.close();
    }
    //根据商品id查询
    public GouWuCheBean query(GouWuCheBean b) {
        GouWuCheBean bean = null;
        SQLiteDatabase db = helper.getReadableDatabase();
        Cursor cursor = db.rawQuery("select * from shopping where shop_id=?",
                new String[] { b.getShop_id() });
        while (cursor.moveToNext()) {
            String id = cursor.getString(cursor.getColumnIndex("shop_id"));
            int num = cursor.getInt(cursor.getColumnIndex("num"));
            GouWuCheBean g=new GouWuCheBean();
            g.setShop_id(id);
            g.setNum(num);
            bean=g;
        }
        return bean;
    }
    //修改
    public void update(int count, String id) {
        SQLiteDatabase db = helper.getWritableDatabase();
        db.execSQL("update shopping set num=? where shop_id=?", new Object[] {
                count, id });
        db.close();
    }
    //全部查询
    public ArrayList<GouWuCheBean> quaryAll() {
        ArrayList<GouWuCheBean> data = new ArrayList<GouWuCheBean>();
        SQLiteDatabase db = helper.getReadableDatabase();
        Cursor cursor = db.rawQuery("select * from shopping", null);
        while (cursor.moveToNext()) {
            String name = cursor.getString(cursor.getColumnIndex("name"));
            String img=cursor.getString(cursor.getColumnIndex("img"));
            Double price=cursor.getDouble(cursor.getColumnIndex("price"));
            String id=cursor.getString(cursor.getColumnIndex("shop_id"));
            int num=cursor.getInt(cursor.getColumnIndex("num"));
            GouWuCheBean bean=new GouWuCheBean(img, price, num, id, name);
            data.add(bean);
        }
        cursor.close();
        db.close();
        return data;
    }
    //删除
    public void delete(ArrayList<String> id){
        SQLiteDatabase db = helper.getWritableDatabase();
        for(String s:id){
            db.delete("shopping", "shop_id=?", new String[]{s});
        }
        db.close();
    }
}