2022-11-5学习内容

1.案例-购物车-数据库准备

1.1ShoppingDBHelper.java

package com.example.chapter06.database;

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

public class ShoppingDBHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "shopping.db";
    // 商品信息表
    private static final String TABLE_GOODS_INFO = "GOODS_INFO";
    // 购物车信息表
    private static final String TABLE_CART_INFO = "CART_INFO";
    private static final int DB_VERSION = 1;
    private static ShoppingDBHelper mHelper = null;
    private SQLiteDatabase mRDB = null;
    private SQLiteDatabase mWDB = null;

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

    // 打开数据库的读连接
    public SQLiteDatabase openReadLink() {
        if (mRDB == null || !mRDB.isOpen()) {
            mRDB = mHelper.getReadableDatabase();
        }
        return mRDB;
    }

    // 打开数据库的写连接
    public SQLiteDatabase openWriteLink() {
        if (mWDB == null || !mWDB.isOpen()) {
            mWDB = mHelper.getWritableDatabase();
        }
        return mWDB;
    }

    // 关闭数据库连接
    public void closeLink() {
        if (mRDB != null && mRDB.isOpen()) {
            mRDB.close();
            mRDB = null;
        }
        if (mWDB != null && mWDB.isOpen()) {
            mWDB.close();
            mWDB = null;
        }
    }

    // 利用单例模式获取数据库帮助器的唯一实例
    public static ShoppingDBHelper getInstance(Context context) {
        if (mHelper == null) {
            mHelper = new ShoppingDBHelper(context);
        }
        return mHelper;
    }

    // 创建数据库，执行建表语句
    @Override
    public void onCreate(SQLiteDatabase db) {
        // 创建商品信息表
        String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_GOODS_INFO +
                "(_ID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," +
                " NAME VARCHAR NOT NULL," +
                " DESCRIPTION VARCHAR NOT NULL," +
                " PRICE FLOAT NOT NULL," +
                " PIC_PATH VARCHAR NOT NULL);";
        db.execSQL(sql);
        // 创建购物车信息表
        sql = "CREATE TABLE IF NOT EXISTS " + TABLE_CART_INFO +
                "(_ID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," +
                " GOODS_ID INTEGER NOT NULL," +
                " COUNT INTEGER NOT NULL);";
        db.execSQL(sql);
    }

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

    }
}

1.2GoodsInfo.java

package com.example.chapter06.entity;

import com.example.chapter06.R;

import java.util.ArrayList;

public class GoodsInfo {

    public int id;
    // 名称
    public String name;
    // 描述
    public String description;
    // 价格
    public float price;
    // 大图的保存路径
    public String picPath;
    // 大图的资源编号
    public int pic;

    // 声明一个手机商品的名称数组
    private static String[] mNameArray = {
            "ipone11", "Mate30", "小米10", "OPPO Reno3", "vivo X30", "荣耀30S"
    };
    // 声明一个手机商品的描述数组
    private static String[] mDescArray = {
            "Apple iPhone11 256GB 绿色 4G全网通手机",
            "华为 HUAWEI Mate30 8GB+256GB 丹霞橙 5G全网通 全面屏手机",
            "小米 MI10 8GB+128GB 钛银黑 5G手机 游戏拍照手机",
            "OPPO Reno3 8GB+128GB 蓝色星夜 双模5G 拍照游戏智能手机",
            "vivo X30 8GB+128GB 绯云 5G全网通 美颜拍照手机",
            "荣耀30S 8GB+128GB 蝶羽红 5G芯片 自拍全面屏手机"
    };
    // 声明一个手机商品的价格数组
    private static float[] mPriceArray = {6299, 4999, 3999, 2999, 2998, 2399};
    // 声明一个手机商品的大图数组
    private static int[] mPicArray = {
            R.drawable.iphone, R.drawable.huawei, R.drawable.xiaoxi,
            R.drawable.oppo, R.drawable.vivo, R.drawable.rongyao
    };

    // 获取默认的手机信息列表
    public static ArrayList<GoodsInfo> getDefaultList() {
        ArrayList<GoodsInfo> goodsList = new ArrayList<>();
        for (int i = 0; i < mNameArray.length; i++) {
            GoodsInfo info = new GoodsInfo();
            info.id = i;
            info.name = mNameArray[i];
            info.description = mDescArray[i];
            info.price = mPriceArray[i];
            info.pic = mPicArray[i];
            goodsList.add(info);
        }
        return goodsList;
    }
}