2022-11-18学习内容

package com.example.chapter06;

import androidx.appcompat.app.AppCompatActivity;

import android.app.AlertDialog;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

import com.example.chapter06.database.ShoppingDBHelper;
import com.example.chapter06.entity.CartInfo;
import com.example.chapter06.entity.GoodsInfo;
import com.example.chapter06.util.ToastUtil;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ShoppingCartActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView tv_count;
    private LinearLayout ll_cart;
    private ShoppingDBHelper mDBHelper;
    // 声明一个购物车中的商品信息列表
    private List<CartInfo> mCartList;
    // 声明一个根据商品编号查找商品信息的映射，把商品信息缓存起来，这样不用每一次都查询数据库
    private Map<Integer, GoodsInfo> mGoodsMap = new HashMap<>();
    private TextView tv_total_price;
    private LinearLayout ll_empty;
    private LinearLayout ll_content;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_shopping_cart);
        TextView tv_title = findViewById(R.id.tv_title);
        tv_title.setText("购物车");
        ll_cart = findViewById(R.id.ll_cart);
        tv_total_price = findViewById(R.id.tv_total_price);

        tv_count = findViewById(R.id.tv_count);
        tv_count.setText(String.valueOf(MyApplication.getInstance().goodsCount));

        mDBHelper = ShoppingDBHelper.getInstance(this);

        findViewById(R.id.iv_back).setOnClickListener(this);
        findViewById(R.id.btn_shopping_channel).setOnClickListener(this);
        findViewById(R.id.btn_clear).setOnClickListener(this);
        findViewById(R.id.btn_settle).setOnClickListener(this);
        ll_empty = findViewById(R.id.ll_empty);
        ll_content = findViewById(R.id.ll_content);
    }

    @Override
    protected void onResume() {
        super.onResume();
        showCart();
    }

    // 展示购物车中的商品列表
    private void showCart() {
        // 移除下面的所有子视图
        ll_cart.removeAllViews();
        // 查询购物车数据库中所有的商品记录
        mCartList = mDBHelper.queryAllCartsInfo();
        if (mCartList.size() == 0) {
            return;
        }
        for (CartInfo info : mCartList) {
            // 根据商品编号查询商品数据库中的商品记录
            GoodsInfo goods = mDBHelper.queryGoodsInfoById(info.goodsId);
            mGoodsMap.put(info.goodsId, goods);

            // 获取布局文件item_cart.xml的根视图
            View view = LayoutInflater.from(this).inflate(R.layout.item_cart, null);
            ImageView iv_thumb = view.findViewById(R.id.iv_thumb);
            TextView tv_name = view.findViewById(R.id.tv_name);
            TextView tv_desc = view.findViewById(R.id.tv_desc);
            TextView tv_count = view.findViewById(R.id.tv_count);
            TextView tv_price = view.findViewById(R.id.tv_price);
            TextView tv_sum = view.findViewById(R.id.tv_sum);

            iv_thumb.setImageURI(Uri.parse(goods.picPath));
            tv_name.setText(goods.name);
            tv_desc.setText(goods.description);
            tv_count.setText(String.valueOf(info.count));
            tv_price.setText(String.valueOf((int)goods.price));
            // 设置商品总价
            tv_sum.setText(String.valueOf((int)info.count * goods.price));

            // 向商品行添加长按事件，长按商品行就删除该商品
            view.setOnLongClickListener(v -> {
                AlertDialog.Builder builder = new AlertDialog.Builder(ShoppingCartActivity.this);
                builder.setMessage("是否从购物车删除" + goods.name + "？");
                builder.setPositiveButton("是", (dialog, which) -> {
                    // 移除当前视图
                    ll_cart.removeView(v);
                    // 删除该商品
                    deleteGoods(info);
                });
                builder.setNegativeButton("否", null);
                builder.create().show();
                return true;
            });

            // 往购物车列表添加该商品行
            ll_cart.addView(view);
        }

        // 重新计算购物车中的商品总金额
        refreshTotalPrice();
    }

    private void deleteGoods(CartInfo info) {
        MyApplication.getInstance().goodsCount -= info.count;
        // 从购物车的数据库中删除商品
        mDBHelper.deleteCartInfoByGoodsId(info.goodsId);
        // 从购物车的列表中删除商品
        CartInfo removed = null;
        for (CartInfo cartInfo : mCartList) {
            if (cartInfo.goodsId == info.goodsId) {
                removed = cartInfo;
                break;
            }
        }
        mCartList.remove(removed);
        // 显示最新的商品数量
        showCount();
        ToastUtil.show(this, "已从购物车删除" + mGoodsMap.get(info.goodsId).name);
        mGoodsMap.remove(info.goodsId);
        // 刷新购物车中所有商品的总金额
        refreshTotalPrice();
    }

    // 显示购物车图标中的商品数量
    private void showCount() {
        tv_count.setText(String.valueOf(MyApplication.getInstance().goodsCount));
        // 购物车中没有商品，显示”空空如也“
        if (MyApplication.getInstance().goodsCount == 0) {
            ll_empty.setVisibility(View.VISIBLE);
            ll_content.setVisibility(View.GONE);
            ll_cart.removeAllViews();
        } else {
            ll_content.setVisibility(View.VISIBLE);
            ll_empty.setVisibility(View.GONE);
        }
    }

    // 重新计算购物车中的商品总金额
    private void refreshTotalPrice() {
        int totalPrice = 0;
        for (CartInfo info : mCartList) {
            GoodsInfo goods = mGoodsMap.get(info.goodsId);
            totalPrice += goods.price * info.count;
        }
        tv_total_price.setText(String.valueOf(totalPrice));
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.iv_back:
                // 点击了返回图标
                // 关闭当前页面
                finish();
                break;

            case R.id.btn_shopping_channel:
                // 从购物车页面跳转到商场页面
                Intent intent = new Intent(this, ShoppingChannelActivity.class);
                intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(intent);
                break;

            case R.id.btn_clear:
                // 清空购物车数据库
                mDBHelper.deleteAllCartInfo();
                MyApplication.getInstance().goodsCount = 0;
                // 显示最新的商品数量
                showCount();
                ToastUtil.show(this, "购物车已清空");
                break;

            case R.id.btn_settle:
                // 点击了“结算”按钮
                AlertDialog.Builder builder = new AlertDialog.Builder(this);
                builder.setTitle("结算商品");
                builder.setMessage("客观抱歉，支付功能尚未开通，请下次再来");
                builder.setPositiveButton("我知道了", null);
                builder.create().show();
                break;
        }
    }
}

package com.example.chapter06.database;

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

import com.example.chapter06.entity.CartInfo;
import com.example.chapter06.entity.GoodsInfo;

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

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) {

    }

    // 添加多条商品信息
    public void insertGoodsInfos(List<GoodsInfo> list) {
        // 插入多条记录，要么全部成功，要么全部失败
        try {
            mWDB.beginTransaction();
            for (GoodsInfo info : list) {
                ContentValues values = new ContentValues();
                values.put("name", info.name);
                values.put("description", info.description);
                values.put("price", info.price);
                values.put("pic_path", info.picPath);
                mWDB.insert(TABLE_GOODS_INFO, null, values);
            }
            mWDB.setTransactionSuccessful();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            mWDB.endTransaction();
        }
    }

    // 查询所有的商品信息
    public List<GoodsInfo> queryAllGoodsInfo() {
        String sql = "select * from " + TABLE_GOODS_INFO;
        List<GoodsInfo> list = new ArrayList<>();
        Cursor cursor = mRDB.rawQuery(sql, null);
        while (cursor.moveToNext()) {
            GoodsInfo info = new GoodsInfo();
            info.id = cursor.getInt(0);
            info.name = cursor.getString(1);
            info.description = cursor.getString(2);
            info.price = cursor.getFloat(3);
            info.picPath = cursor.getString(4);
            list.add(info);
        }
        return list;
    }

    // 添加商品到购物车
    public void insertCartInfo(int goodsId) {
        // 如果购物车中不存在该商品，添加一条信息
        CartInfo cartInfo = queryCartInfoByGoodsId(goodsId);
        ContentValues values = new ContentValues();
        values.put("goods_id", goodsId);
        if (cartInfo == null) {
            values.put("count", 1);
            mWDB.insert(TABLE_CART_INFO,null,values);
        } else {
            // 如果购物车中已经存在该商品，更新商品数量
            values.put("_id", cartInfo.id);
            values.put("count", ++cartInfo.count);
            mWDB.update(TABLE_CART_INFO,values,"_id=?",new String[]{String.valueOf(cartInfo.id)});
        }
    }

    private CartInfo queryCartInfoByGoodsId(int goodsId) {
        Cursor cursor = mRDB.query(TABLE_CART_INFO, null, "goods_id=?", new String[]{String.valueOf(goodsId)}, null, null, null);
        CartInfo info = null;
        if (cursor.moveToNext()) {
            info = new CartInfo();
            info.id = cursor.getInt(0);
            info.goodsId = cursor.getInt(1);
            info.count = cursor.getInt(2);
        }
        return info;
    }

    // 统计购物车中商品的总数量
    public int countCartInfo() {
        int count = 0;
        String sql = "select sum(count) from " + TABLE_CART_INFO;
        Cursor cursor = mRDB.rawQuery(sql, null);
        if (cursor.moveToNext()) {
            count = cursor.getInt(0);
        }
        return count;
    }

    // 查询购物车中所有的信息列表
    public List<CartInfo> queryAllCartsInfo() {
        List<CartInfo> list = new ArrayList<>();
        Cursor cursor = mRDB.query(TABLE_CART_INFO, null, null, null, null, null, null);
        while (cursor.moveToNext()) {
            CartInfo info = new CartInfo();
            info.id = cursor.getInt(0);
            info.goodsId = cursor.getInt(1);
            info.count = cursor.getInt(2);
            list.add(info);
        }
        return list;
    }

    // 根据商品ID查询商品信息
    public GoodsInfo queryGoodsInfoById(int goodsId) {
        GoodsInfo info = null;
        Cursor cursor = mRDB.query(TABLE_GOODS_INFO, null, "_id=?", new String[]{String.valueOf(goodsId)}, null, null, null);
        if (cursor.moveToNext()) {
            info = new GoodsInfo();
            info.id = cursor.getInt(0);
            info.name = cursor.getString(1);
            info.description = cursor.getString(2);
            info.price = cursor.getFloat(3);
            info.picPath = cursor.getString(4);
        }
        return info;
    }

    // 根据商品ID删除购物车信息
    public void deleteCartInfoByGoodsId(int goodsId) {
        mWDB.delete(TABLE_CART_INFO,"goods_id=?",new String[]{String.valueOf(goodsId)});
    }

    // 删除所有购物车信息
    public void deleteAllCartInfo() {
        mWDB.delete(TABLE_CART_INFO,"1=1",null);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:tools="http://schemas.android.com/tools"
    android:background="@color/orange"
    android:orientation="vertical">

    <include layout="@layout/title_shopping" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <ImageView
                android:id="@+id/iv_goods_pic"
                android:layout_width="match_parent"
                android:layout_height="350dp"
                android:scaleType="fitCenter"
                tools:src="@drawable/xiaomi" />

            <TextView
                android:id="@+id/tv_goods_price"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:paddingLeft="5dp"
                android:textColor="@color/red"
                android:textSize="22sp"
                tools:text="1990" />

            <TextView
                android:id="@+id/tv_goods_desc"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:paddingLeft="5dp"
                android:textColor="@color/black"
                android:textSize="15sp"
                tools:text="小米 MI10 8GB+128GB 钛银黑 5G手机 游戏拍照手机" />

            <Button
                android:id="@+id/btn_add_cart"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="加入购物车"
                android:textColor="@color/black"
                android:textSize="17sp" />
        </LinearLayout>
    </ScrollView>

</LinearLayout>

package com.example.chapter06;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import com.example.chapter06.database.ShoppingDBHelper;
import com.example.chapter06.entity.GoodsInfo;
import com.example.chapter06.util.ToastUtil;

public class ShoppingDetailActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView tv_title;
    private TextView tv_count;
    private TextView tv_goods_price;
    private TextView tv_goods_desc;
    private ImageView iv_goods_pic;
    private ShoppingDBHelper mDBHelper;
    private int mGoodsId;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_shopping_detail);
        tv_title = findViewById(R.id.tv_title);
        tv_count = findViewById(R.id.tv_count);
        tv_goods_price = findViewById(R.id.tv_goods_price);
        tv_goods_desc = findViewById(R.id.tv_goods_desc);
        iv_goods_pic = findViewById(R.id.iv_goods_pic);
        findViewById(R.id.iv_back).setOnClickListener(this);
        findViewById(R.id.iv_cart).setOnClickListener(this);
        findViewById(R.id.btn_add_cart).setOnClickListener(this);

        tv_count.setText(String.valueOf(MyApplication.getInstance().goodsCount));

        mDBHelper = ShoppingDBHelper.getInstance(this);
    }

    @Override
    protected void onResume() {
        super.onResume();
        showDetail();
    }

    private void showDetail() {
        // 获取上一个页面传来的商品编号
        mGoodsId = getIntent().getIntExtra("goods_id", 0);
        if (mGoodsId > 0) {
            // 根据商品编号查询商品数据库中的商品记录
            GoodsInfo info = mDBHelper.queryGoodsInfoById(mGoodsId);
            tv_title.setText(info.name);
            tv_goods_desc.setText(info.description);
            tv_goods_price.setText(String.valueOf((int)info.price));
            iv_goods_pic.setImageURI(Uri.parse(info.picPath));

        }
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.iv_back:
                finish();
                break;
            case R.id.iv_cart:
                Intent intent = new Intent(this, ShoppingCartActivity.class);
                startActivity(intent);
                break;
            case R.id.btn_add_cart:
                addToCart(mGoodsId);
                break;
        }
    }

    private void addToCart(int mGoodsId) {
        // 购物车商品数量+1
        int count = ++MyApplication.getInstance().goodsCount;
        tv_count.setText(String.valueOf(count));
        mDBHelper.insertCartInfo(mGoodsId);
        ToastUtil.show(this, "成功添加至购物车");
    }
}

// 展示购物车中的商品列表
    private void showCart() {
        // 移除下面的所有子视图
        ll_cart.removeAllViews();
        // 查询购物车数据库中所有的商品记录
        mCartList = mDBHelper.queryAllCartsInfo();
        if (mCartList.size() == 0) {
            return;
        }
        for (CartInfo info : mCartList) {
            // 根据商品编号查询商品数据库中的商品记录
            GoodsInfo goods = mDBHelper.queryGoodsInfoById(info.goodsId);
            mGoodsMap.put(info.goodsId, goods);

            // 获取布局文件item_cart.xml的根视图
            View view = LayoutInflater.from(this).inflate(R.layout.item_cart, null);
            ImageView iv_thumb = view.findViewById(R.id.iv_thumb);
            TextView tv_name = view.findViewById(R.id.tv_name);
            TextView tv_desc = view.findViewById(R.id.tv_desc);
            TextView tv_count = view.findViewById(R.id.tv_count);
            TextView tv_price = view.findViewById(R.id.tv_price);
            TextView tv_sum = view.findViewById(R.id.tv_sum);

            iv_thumb.setImageURI(Uri.parse(goods.picPath));
            tv_name.setText(goods.name);
            tv_desc.setText(goods.description);
            tv_count.setText(String.valueOf(info.count));
            tv_price.setText(String.valueOf((int)goods.price));
            // 设置商品总价
            tv_sum.setText(String.valueOf((int)info.count * goods.price));

            // 向商品行添加长按事件，长按商品行就删除该商品
            view.setOnLongClickListener(v -> {
                AlertDialog.Builder builder = new AlertDialog.Builder(ShoppingCartActivity.this);
                builder.setMessage("是否从购物车删除" + goods.name + "？");
                builder.setPositiveButton("是", (dialog, which) -> {
                    // 移除当前视图
                    ll_cart.removeView(v);
                    // 删除该商品
                    deleteGoods(info);
                });
                builder.setNegativeButton("否", null);
                builder.create().show();
                return true;
            });

            // 给商品行添加点击事件。点击商品行跳到商品的详情页
            view.setOnClickListener(v -> {
                Intent intent = new Intent(ShoppingCartActivity.this, ShoppingDetailActivity.class);
                intent.putExtra("goods_id", goods.id);
                startActivity(intent);
            });

            // 往购物车列表添加该商品行
            ll_cart.addView(view);
        }

        // 重新计算购物车中的商品总金额
        refreshTotalPrice();
    }

private void showGoods() {
        // 商品条目是一个线性布局，设置布局的宽度为屏幕的一半
        int screenWidth = getResources().getDisplayMetrics().widthPixels;
        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(screenWidth / 2, LinearLayout.LayoutParams.WRAP_CONTENT);
        // 查询商品数据库中的所有商品记录
        List<GoodsInfo> list = mDBHelper.queryAllGoodsInfo();

        // 移除下面的所有子视图
        gl_channel.removeAllViews();

        for (GoodsInfo info : list) {
            // 获取布局文件item_goods.xml的根视图
            View view = LayoutInflater.from(this).inflate(R.layout.item_goods, null);
            ImageView iv_thumb = view.findViewById(R.id.iv_thumb);
            TextView tv_name = view.findViewById(R.id.tv_name);
            TextView tv_price = view.findViewById(R.id.tv_price);
            Button btn_add = view.findViewById(R.id.btn_add);

            // 给控件设置值
            iv_thumb.setImageURI(Uri.parse(info.picPath));
            tv_name.setText(info.name);
            tv_price.setText(String.valueOf((int)info.price));

            // 添加到购物车
            btn_add.setOnClickListener(v -> {
                addToCart(info.id, info.name);
            });

            // 点击商品图片，跳转到商品详情页面
            iv_thumb.setOnClickListener(v -> {
                Intent intent = new Intent(ShoppingChannelActivity.this, ShoppingDetailActivity.class);
                intent.putExtra("goods_id", info.id);
                startActivity(intent);
            });

            // 把商品视图添加到网格布局
            gl_channel.addView(view, params);
        }
    }