Android -- 购物车

简单购物车案例

购物车功能描述

        第一次进入购物车页面，购物车里面是空的，同时提示去逛手机商场， 如 首次进入的页面 图所示。接着去商场页面选购手机，随便挑了几部手机加入购物车，再返回购物车页面，即可看 到购物车的商品列表，如 购物车已选列表图 所示，有商品图片、名称、数量、单价、总价等等信息。当然购物车并 不仅仅只是展示待购买的商品，还要支持最终购买的结算操作、支持清空购物车，长按删除单项订单等功能。

        购物车的存在感很强，不仅仅在购物车页面才能看到购物车。往往在商场页面，甚至商品详情页面，都 会看到某个角落冒出购物车图标。一旦有新商品加入购物车，购物车图标上的商品数量立马加一。当然，用户也能点击购物车图标直接跳到购物车页面。商场页面除了商品列表之外，页面右上角还有一个购物车图标，用户把商品加购物车，那么图标上的数字也会加一。

功能需求

• 购物车存放着用户准备购买的商品，一开始是空的，随着商品被加入购物车，购物车中就会显示已添加的商品列表。

• 除了购物车页面，其它页面（如商场频道页面、商品详情页面），都可能在右上角或者右 下角找到购物车图标。购物车图标上会显示已添加的商品数量，且商品数量是实时更新的。

• 购物车页面、商场频道页面、商品详情页面多处都会显示商品的小图或者大图

界面设计

• 线性布局LinearLayout：购物车界面从上往下排列，垂直方向的线性布局

• 网格布局GridLayout：商场页面的陈列橱柜，允许分行分列展示商品

• 相对布局RelativeLayout：页面右上角的购物车图标，图标右上角又有数字标记，按照指定方位排列控件

• 其他常见控件尚有文本视图TextView、图像视图ImageView，按钮控件Button等

存储技术

• 数据库SQLite：最直观的是数据库，购物车里的商品列表一定放在SQLite中，增删改查

• 全局内存：购物车图标右上角的数字表示购物车中的商品数量，该数值建议保存在全局内存中，这样不必每次都到数据库中执行count操作。

• 存储卡文件：App把下载的商品图片保存在存储卡中，这样下次就能直接从存储卡获取商品图片，加快浏览速度。

• 共享参数SharedPreferences：是否首次访问网络图片，这个标志位推荐放在共享参数中， 需要持久化存储，并且只有一个参数信息

效果图

首次进入的页面图

商品展示列表图

购物车已选列表图

 手机详情页面图

长按删除订单图

图片

主程序

ShoppingChannelActivity.java

package com.kcs.shoppingcart;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.GridView;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

import com.kcs.shoppingcart.adapter.GoodsAdapter;
import com.kcs.shoppingcart.datebase.ShoppingDBHelper;
import com.kcs.shoppingcart.entity.GoodsInfo;
import com.kcs.shoppingcart.utils.ToastUtil;

import java.util.List;

public class ShoppingChannelActivity extends AppCompatActivity implements View.OnClickListener, GoodsAdapter.AddCartListener {

    /**
     * 声明一个商品数据库的帮助器对象
     */
    private ShoppingDBHelper mDBHelper;
    private TextView tv_count;
    private GridView gv_channel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_shopping_channel);
        TextView tv_title = findViewById(R.id.tv_title);
        tv_title.setText("手机商场");

        tv_count = findViewById(R.id.tv_count);
        gv_channel = findViewById(R.id.gv_channel);
        findViewById(R.id.iv_back).setOnClickListener(this);
        findViewById(R.id.iv_cart).setOnClickListener(this);

        mDBHelper = ShoppingDBHelper.getInstance(this);
        mDBHelper.openReadLink();
        mDBHelper.openWriteLink();

        // 从数据库查询出商品信息，并展示
        showGoods();
    }

    @Override
    protected void onResume() {
        super.onResume();
        // 查询购物车商品总数，并展示
        showCartInfoTotal();
    }

    /**
     * 查询购物车商品总数，并展示
     */
    private void showCartInfoTotal() {
        int count = mDBHelper.countCartInfo();
        MyApplication.getInstance().goodsCount = count;
        tv_count.setText(String.valueOf(count));
    }

    private void showGoods() {
        // 查询商品数据库中的所有商品记录
        List<GoodsInfo> list = mDBHelper.queryAllGoodsInfo();
        GoodsAdapter adapter = new GoodsAdapter(this, list,this);
        gv_channel.setAdapter(adapter);
    }

    /**
     *  把指定编号的商品添加到购物车
     * @param goodsId
     * @param goodsName
     */

    @Override
    public void addToCart(int goodsId, String goodsName) {
        // 购物车商品数量+1
        int count = ++MyApplication.getInstance().goodsCount;
        tv_count.setText(String.valueOf(count));
        mDBHelper.insertCartInfo(goodsId);
        ToastUtil.show(this, "已添加一部" + goodsName + "到购物车");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mDBHelper.closeLink();
    }

    @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.iv_cart:
                // 点击了购物车图标
                // 从商场页面跳到购物车页面
                Intent intent = new Intent(this, ShoppingCartActivity.class);
                // 设置启动标志，避免多次返回同一页面的
                intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(intent);
                break;
            default:
                break;
        }
    }
}

ShoppingDetailActivity.java

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.dongnaoedu.chapter06.database.ShoppingDBHelper;
import com.dongnaoedu.chapter06.enity.GoodsInfo;
import com.dongnaoedu.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 goodsId) {
        // 购物车商品数量+1
        int count = ++MyApplication.getInstance().goodsCount;
        tv_count.setText(String.valueOf(count));
        mDBHelper.insertCartInfo(goodsId);
        ToastUtil.show(this, "成功添加至购物车");
    }
}

ShoppingCartActivity.java

package com.kcs.shoppingcart;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import com.kcs.shoppingcart.adapter.CartAdapter;
import com.kcs.shoppingcart.datebase.ShoppingDBHelper;
import com.kcs.shoppingcart.entity.CartInfo;
import com.kcs.shoppingcart.entity.GoodsInfo;
import com.kcs.shoppingcart.utils.ToastUtil;

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

public class ShoppingCartActivity extends AppCompatActivity implements View.OnClickListener, AdapterView.OnItemClickListener, AdapterView.OnItemLongClickListener {

    private TextView tv_count;
    private ListView lv_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，这样不用每一次都去查询数据库
     */
    private Map<Integer, GoodsInfo> mGoodsMap = new HashMap<>();
    private TextView tv_total_price;
    private LinearLayout ll_empty;
    private LinearLayout ll_content;
    private CartAdapter mCartAdapter;

    @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");
        lv_cart = findViewById(R.id.lv_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() {
        // 查询购物车数据库中所有的商品记录
        mCartList = mDBHelper.queryAllCartInfo();
        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);
            info.goods = goods;
        }
        mCartAdapter = new CartAdapter(this, mCartList);
        lv_cart.setAdapter(mCartAdapter);
        // 给商品行添加点击事件。点击商品行跳到商品的详情页
        lv_cart.setOnItemClickListener(this);
        // 给商品行添加长按事件。长按商品行就删除该商品
        lv_cart.setOnItemLongClickListener(this);

        // 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);
            // 通知适配器发生了数据变化
            mCartAdapter.notifyDataSetChanged();
        } 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:
                // 从购物车页面跳到商场页面
                Intent intent = new Intent(this, com.kcs.shoppingcart.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("客官抱歉，支付功能尚未开通");
                builder.setPositiveButton("我知道了", null);
                builder.create().show();
                break;
            default:
                break;
        }
    }

    /**
     * 给商品行添加点击事件。点击商品行跳到商品的详情页
     */
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Intent intent = new Intent(ShoppingCartActivity.this, com.kcs.shoppingcart.ShoppingDetailActivity.class);
        intent.putExtra("goods_id", mCartList.get(position).goodsId);
        startActivity(intent);
    }

    /**
     *给商品行添加长按事件。长按商品行就删除该商品
     */
    @Override
    public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
        CartInfo info = mCartList.get(position);
        AlertDialog.Builder builder = new AlertDialog.Builder(ShoppingCartActivity.this);
        builder.setMessage("是否从购物车删除" + info.goods.name + "？");
        builder.setPositiveButton("是", (dialog, which) -> {
            // 从集合中移除数据
            mCartList.remove(position);
            // 通知适配器发生了数据变化
            mCartAdapter.notifyDataSetChanged();
            // 删除该商品
            deleteGoods(info);
        });
        builder.setNegativeButton("否", null);
        builder.create().show();
        return true;
    }
}

MyApplication.java

package com.dongnaoedu.chapter06;

import android.app.Application;
import android.content.res.Configuration;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
import android.util.Log;


import androidx.annotation.NonNull;
import androidx.room.Room;

import com.dongnaoedu.chapter06.database.ShoppingDBHelper;
import com.dongnaoedu.chapter06.enity.GoodsInfo;
import com.dongnaoedu.chapter06.util.FileUtil;
import com.dongnaoedu.chapter06.util.SharedUtil;

import java.io.File;
import java.util.HashMap;
import java.util.List;

public class MyApplication extends Application {

    // 购物车中的商品总数量
    public int goodsCount;

    public static MyApplication getInstance() {
        return mApp;
    }


    //在App启动时调用
    @Override
    public void onCreate() {
        super.onCreate();
        mApp = this;
        Log.d("ning", "MyApplication onCreate");

        // 初始化商品信息
        initGoodsInfo();
    }

    private void initGoodsInfo() {
        // 获取共享参数保存的是否首次打开参数
        boolean isFirst = SharedUtil.getInstance(this).readBoolean("first", true);
        // 获取当前App的私有下载路径
        String directory = getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS).toString() + File.separatorChar;
        if (isFirst) {
            // 模拟网络图片下载
            List<GoodsInfo> list = GoodsInfo.getDefaultList();
            for (GoodsInfo info : list) {
                Bitmap bitmap = BitmapFactory.decodeResource(getResources(), info.pic);
                String path = directory + info.id + ".jpg";
                // 往存储卡保存商品图片
                FileUtil.saveImage(path, bitmap);
                // 回收位图对象
                bitmap.recycle();
                info.picPath = path;
            }
            // 打开数据库，把商品信息插入到表中
            ShoppingDBHelper dbHelper = ShoppingDBHelper.getInstance(this);
            dbHelper.openWriteLink();
            dbHelper.insertGoodsInfos(list);
            dbHelper.closeLink();
            // 把是否首次打开写入共享参数
            SharedUtil.getInstance(this).writeBoolean("first", false);
        }
    }

}

适配器

 package：adapter

CartAdapter.java

package com.kcs.shoppingcart.adapter;

import android.content.Context;
import android.net.Uri;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;


import com.kcs.shoppingcart.R;
import com.kcs.shoppingcart.entity.CartInfo;

import java.util.List;

public class CartAdapter extends BaseAdapter {

    private Context mContext;
    private List<CartInfo> mCartList;

    public CartAdapter(Context mContext, List<CartInfo> mCartList) {
        this.mContext = mContext;
        this.mCartList = mCartList;
    }

    @Override
    public int getCount() {
        return mCartList.size();
    }

    @Override
    public Object getItem(int position) {
        return mCartList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        if (convertView == null) {
            holder = new ViewHolder();
            // 获取布局文件item_cart.xml的根视图
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_cart, null);
            holder.iv_thumb = convertView.findViewById(R.id.iv_thumb);
            holder.tv_name = convertView.findViewById(R.id.tv_name);
            holder.tv_desc = convertView.findViewById(R.id.tv_desc);
            holder.tv_count = convertView.findViewById(R.id.tv_count);
            holder.tv_price = convertView.findViewById(R.id.tv_price);
            holder.tv_sum = convertView.findViewById(R.id.tv_sum);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        CartInfo info = mCartList.get(position);
        holder.iv_thumb.setImageURI(Uri.parse(info.goods.picPath));
        holder.tv_name.setText(info.goods.name);
        holder.tv_desc.setText(info.goods.description);
        holder.tv_count.setText(String.valueOf(info.count));
        holder.tv_price.setText(String.valueOf((int) info.goods.price));
        // 设置商品总价
        holder.tv_sum.setText(String.valueOf((int) (info.count * info.goods.price)));
        return convertView;
    }

    public final class ViewHolder {
        public ImageView iv_thumb;
        public TextView tv_name;
        public TextView tv_desc;
        public TextView tv_count;
        public TextView tv_price;
        public TextView tv_sum;

    }
}

GoodsAdapter.java

package com.kcs.shoppingcart.adapter;

import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import com.kcs.shoppingcart.R;
import com.kcs.shoppingcart.ShoppingDetailActivity;
import com.kcs.shoppingcart.entity.GoodsInfo;

import java.util.List;

public class GoodsAdapter extends BaseAdapter {

    private Context mContext;
    private List<GoodsInfo> mGoodsInfo;

    public GoodsAdapter(Context mContext, List<GoodsInfo> mGoodsInfo, AddCartListener mAddCartListener) {
        this.mContext = mContext;
        this.mGoodsInfo = mGoodsInfo;
        this.mAddCartListener = mAddCartListener;
    }

    @Override
    public int getCount() {
        return mGoodsInfo.size();
    }

    @Override
    public Object getItem(int position) {
        return position;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        GoodsInfo info = mGoodsInfo.get(position);
        ViewHolder holder;
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_goods, null);
            holder = new ViewHolder();
            holder.iv_thumb = convertView.findViewById(R.id.iv_thumb);
            holder.tv_name = convertView.findViewById(R.id.tv_name);
            holder.tv_price = convertView.findViewById(R.id.tv_price);
            holder.btn_add = convertView.findViewById(R.id.btn_add);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }


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

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

        //点击商品图片，跳转到商品详情页面

        holder.iv_thumb.setOnClickListener(v -> {
            Intent intent = new Intent(mContext, ShoppingDetailActivity.class);
            intent.putExtra("goods_id", info.id);
            mContext.startActivity(intent);
        });

        return convertView;
    }

    public final class ViewHolder {
        public ImageView iv_thumb;
        public TextView tv_name;
        public TextView tv_price;
        public Button btn_add;
    }

    /**
     * 声明一个加入购物车的监听器对象
     */
    private AddCartListener mAddCartListener;

    /**
     * 定义一个加入购物车的监听器接口
     */
    public interface AddCartListener {
        void addToCart(int goodsId, String goodsName);
    }
}

工具类

package util:

ToastUitl.java

package com.dongnaoedu.chapter06.util;

import android.content.Context;
import android.widget.Toast;

public class ToastUtil {

    public static void show(Context ctx, String desc) {
        Toast.makeText(ctx, desc, Toast.LENGTH_SHORT).show();
    }

}

SharedUtil.java

import android.content.Context;
import android.content.SharedPreferences;

public class SharedUtil {

    private static SharedUtil mUtil;
    private SharedPreferences preferences;

    public static SharedUtil getInstance(Context ctx) {
        if (mUtil == null) {
            mUtil = new SharedUtil();
            mUtil.preferences = ctx.getSharedPreferences("shopping", Context.MODE_PRIVATE);
        }
        return mUtil;
    }

    public void writeBoolean(String key, boolean value) {
        SharedPreferences.Editor editor = preferences.edit();
        editor.putBoolean(key, value);
        editor.commit();
    }

    public boolean readBoolean(String key, boolean defaultValue) {
        return preferences.getBoolean(key, defaultValue);
    }

}

FileUtil.java

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class FileUtil {

    // 把位图数据保存到指定路径的图片文件
    public static void saveImage(String path, Bitmap bitmap) {
        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(path);
            // 把位图数据压缩到文件输出流中
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    // 从指定路径的图片文件中读取位图数据
    public static Bitmap openImage(String path) {
        Bitmap bitmap = null;
        FileInputStream fis = null;
        try {
            fis = new FileInputStream(path);
            bitmap = BitmapFactory.decodeStream(fis);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (fis != null) {
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return bitmap;
    }
}

实体类 

package pojo：

CarInfo.java

package com.kcs.shoppingcart.entity;

//购物车信息
public class CartInfo {
    public int id;
    /**
     * 商品编号
     */
    public int goodsId;
    /**
     * 商品数量
     */
    public int count;
    /**
     * 商品信息
     */
    public GoodsInfo goods;

    public CartInfo() {
    }

    public CartInfo(int id, int goodsId, int count) {
        this.id = id;
        this.goodsId = goodsId;
        this.count = count;
        this.goods = new GoodsInfo();
    }
}

GoodsInfo.java

import com.dongnaoedu.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 = {
            "iPhone11", "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.xiaomi,
            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<GoodsInfo>();
        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;
    }
}

购物车数据库类

package 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.dongnaoedu.chapter06.enity.CartInfo;
import com.dongnaoedu.chapter06.enity.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);
    }

    // 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;
    }

    // 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;
        }
    }

    // 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);
        }
        cursor.close();
        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)});
        }
    }

    // 根据商品信息ID查询购物车信息
    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> queryAllCartInfo() {
        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);
    }
}

布局文件

activity_shopping_channel.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/orange"
    android:orientation="vertical" >

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

    <GridView
        android:id="@+id/gv_channel"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:numColumns="2" />

</LinearLayout>

activity_shopping_detail.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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>

activity_shopping_car.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/orange"
    android:orientation="vertical">

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

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

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

            <LinearLayout
                android:id="@+id/ll_content"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="vertical"
                android:visibility="visible">

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

                    <TextView
                        android:layout_width="85dp"
                        android:layout_height="wrap_content"
                        android:gravity="center"
                        android:text="图片"
                        android:textColor="@color/black"
                        android:textSize="15sp" />

                    <TextView
                        android:layout_width="0dp"
                        android:layout_height="wrap_content"
                        android:layout_weight="3"
                        android:gravity="center"
                        android:text="名称"
                        android:textColor="@color/black"
                        android:textSize="15sp" />

                    <TextView
                        android:layout_width="0dp"
                        android:layout_height="wrap_content"
                        android:layout_weight="1"
                        android:gravity="center"
                        android:text="数量"
                        android:textColor="@color/black"
                        android:textSize="15sp" />

                    <TextView
                        android:layout_width="0dp"
                        android:layout_height="wrap_content"
                        android:layout_weight="1"
                        android:gravity="center"
                        android:text="单价"
                        android:textColor="@color/black"
                        android:textSize="15sp" />

                    <TextView
                        android:layout_width="0dp"
                        android:layout_height="wrap_content"
                        android:layout_weight="1"
                        android:gravity="center"
                        android:text="总价"
                        android:textColor="@color/black"
                        android:textSize="15sp" />

                </LinearLayout>

                <LinearLayout
                    android:id="@+id/ll_cart"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical" />

                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal"
                    android:padding="0dp">

                    <Button
                        android:id="@+id/btn_clear"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:gravity="center"
                        android:text="清空"
                        android:textColor="@color/black"
                        android:textSize="17sp" />

                    <TextView
                        android:layout_width="0dp"
                        android:layout_height="wrap_content"
                        android:layout_weight="1"
                        android:gravity="center|right"
                        android:text="总金额："
                        android:textColor="@color/black"
                        android:textSize="17sp" />

                    <TextView
                        android:id="@+id/tv_total_price"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_marginRight="10dp"
                        android:gravity="center|left"
                        android:textColor="@color/red"
                        android:textSize="25sp" />

                    <Button
                        android:id="@+id/btn_settle"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:gravity="center"
                        android:text="结算"
                        android:textColor="@color/black"
                        android:textSize="17sp" />
                </LinearLayout>

            </LinearLayout>

            <LinearLayout
                android:id="@+id/ll_empty"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="vertical"
                android:visibility="gone"
                tools:visibility="visible">

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginTop="100dp"
                    android:layout_marginBottom="100dp"
                    android:gravity="center"
                    android:text="哎呀，购物车空空如也，快去选购商品吧"
                    android:textColor="@color/black"
                    android:textSize="17sp" />

                <Button
                    android:id="@+id/btn_shopping_channel"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:gravity="center"
                    android:text="逛逛手机商场"
                    android:textColor="@color/black"
                    android:textSize="17sp" />
            </LinearLayout>
        </RelativeLayout>
    </ScrollView>

</LinearLayout>

购物车列表清单

item_cart.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/white"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/iv_thumb"
        android:layout_width="85dp"
        android:layout_height="85dp"
        android:scaleType="fitCenter"
        tools:src="@drawable/xiaomi"/>

    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="3"
        android:orientation="vertical">

        <TextView
            android:id="@+id/tv_name"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="2"
            android:gravity="left|center"
            android:textColor="@color/black"
            android:textSize="17sp"
            tools:text="小米手机"/>

        <TextView
            android:id="@+id/tv_desc"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="3"
            android:gravity="left|center"
            android:textColor="@color/black"
            android:textSize="12sp"
            tools:text="小米 MI10 8GB+128GB 钛银黑 5G手机 游戏拍照手机"/>
    </LinearLayout>

    <TextView
        android:id="@+id/tv_count"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:gravity="center"
        android:textColor="@color/black"
        android:textSize="17sp"
        tools:text="2"/>

    <TextView
        android:id="@+id/tv_price"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:gravity="right|center"
        android:textColor="@color/black"
        android:textSize="15sp"
        tools:text="1000"/>

    <TextView
        android:id="@+id/tv_sum"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1.2"
        android:gravity="right|center"
        android:textColor="@color/red"
        android:textSize="17sp"
        tools:text="2000"/>

</LinearLayout>

货物清单数据布局文件

item_goods.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/ll_item"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:background="@color/white"
    android:gravity="center"
    android:orientation="vertical">

    <TextView
        android:id="@+id/tv_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textColor="@color/black"
        android:textSize="17sp"
        tools:text="小米手机" />

    <ImageView
        android:id="@+id/iv_thumb"
        android:layout_width="180dp"
        android:layout_height="150dp"
        android:scaleType="fitCenter"
        tools:src="@drawable/xiaomi" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="45dp"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_price"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="2"
            android:gravity="center"
            android:textColor="@color/red"
            android:textSize="15sp"
            tools:text="20" />

        <Button
            android:id="@+id/btn_add"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="3"
            android:gravity="center"
            android:text="加入购物车"
            android:textColor="@color/black"
            android:textSize="15sp" />
    </LinearLayout>

</LinearLayout>

顶部布局文件

title_shopping.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="50dp"
    android:background="#aaaaff" >
    
    <ImageView
        android:id="@+id/iv_back"
        android:layout_width="50dp"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:padding="10dp"
        android:scaleType="fitCenter"
        android:src="@drawable/ic_back" />

    <TextView
        android:id="@+id/tv_title"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_centerInParent="true"
        android:gravity="center"
        android:textColor="@color/black"
        android:textSize="20sp" />
    
    <ImageView
        android:id="@+id/iv_cart"
        android:layout_width="50dp"
        android:layout_height="match_parent"
        android:layout_alignParentRight="true"
        android:scaleType="fitCenter"
        android:src="@drawable/cart" />
    
    <TextView
        android:id="@+id/tv_count"
        android:layout_width="20dp"
        android:layout_height="20dp"
        android:layout_alignParentTop="true"
        android:layout_toRightOf="@+id/iv_cart"
        android:layout_marginLeft="-20dp"
        android:gravity="center"
        android:background="@drawable/shape_oval_red"
        android:text="0"
        android:textColor="@color/white"
        android:textSize="15sp" />
    
</RelativeLayout>

资源文件

shape_oval_red.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">

    <solid android:color="#ff6666" />

</shape>

colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="purple_200">#FFBB86FC</color>
    <color name="purple_500">#FF6200EE</color>
    <color name="purple_700">#FF3700B3</color>
    <color name="teal_200">#FF03DAC5</color>
    <color name="teal_700">#FF018786</color>
    <color name="black">#FF000000</color>
    <color name="white">#FFFFFFFF</color>
    <color name="grey">#cccccc</color>
    <color name="orange">#ffffdd</color>
    <color name="red">#ff0000</color>
</resources>

AndroidManifest.xml

把自己写的MyApplication配置上 

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.kcs.shoppingcart">

    <application
        android:name=".MyApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.ShoppingCart">

        <activity
            android:name=".ShoppingCartActivity"
            android:exported="true" />
        <activity
            android:name=".ShoppingDetailActivity"
            android:exported="true" />
        <activity
            android:name=".ShoppingChannelActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>