如何在Android应用中实现添加商品到购物车的功能？

Android添加商品到购物车

在Android应用开发中，实现将商品添加到购物车的功能是一个常见的需求，本文将详细介绍如何在Android应用中实现这一功能，包括创建适配器、设置点击事件、管理购物车中的商品数量和总价等，以下是具体实现步骤：

一、创建数据库

为了实现购物车功能，首先需要创建两个数据库：商品列表数据库和购物车数据库，商品列表数据库用于存放商品信息（如商品ID、图标、标题、价格），购物车数据库则保存商品ID以及商品数量。

1. 商品列表数据库（GoodsListDatabase.java）

package com.domain.mainView.database;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class GoodsListDatabase extends SQLiteOpenHelper {
    private static final String TAG = GoodsListDatabase.class.getSimpleName();
    // 定义创建数据表dict的SQL语句
    // 创建表时，定义的单个列的约束
    public static final String CREATE_GOODS_SQL =
            "create table goods(dbId integer, dbIcon integer, dbTitle text, dbPrice text, UNIQUE(dbId))";
    public GoodsListDatabase(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_GOODS_SQL);
        Log.i(TAG, "onCreate: 商品列表数据库创建成功");
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("drop table if exists goods");
        onCreate(db);
    }
}

2. 购物车数据库（ShoppingCarDatabase.java）

package com.domain.mainView.database;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class ShoppingCarDatabase extends SQLiteOpenHelper {
    private static final String TAG = ShoppingCarDatabase.class.getSimpleName();
    // 定义创建数据表dict的SQL语句
    public static final String CREATE_CART_SQL =
            "create table cart(carId integer primary key autoincrement, dbId integer, dbQuantity integer, UNIQUE(dbId))";
    public ShoppingCarDatabase(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_CART_SQL);
        Log.i(TAG, "onCreate: 购物车数据库创建成功");
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("drop table if exists cart");
        onCreate(db);
    }
}

二、封装类

创建两个封装类：Goods.java用于封装对商品的操作，Car.java用于封装对购物车的操作。

1. 商品类（Goods.java）

package com.domain.mainView.model;
public class Goods {
    private long dbId;
    private int dbIcon;
    private String dbTitle;
    private String dbPrice;
    // Getter and Setter methods...
}

2. 购物车类（Car.java）

package com.domain.mainView.model;
public class Car {
    private long carId; // 这个字段可以不定义，因为自增主键不需要手动设置
    private long dbId;
    private int dbQuantity;
    // Getter and Setter methods...
}

三、创建全局Context

在MyApplication.java中创建全局Context，以便在应用的任何地方都可以访问到数据库。

package com.domain.mainView;
import android.app.Application;
public class MyApplication extends Application {
    private static MyApplication instance;
    @Override
    public void onCreate() {
        super.onCreate();
        instance = this;
    }
    public static MyApplication getInstance() {
        return instance;
    }
}

四、分类和购物车页面

1. CategoryRightAdapter.java

package com.domain.mainView.adapter;
import android.content.Context;
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.domain.mainView.R;
import com.domain.mainView.model.Goods;
import java.util.List;
public class CategoryRightAdapter extends BaseAdapter {
    private List<Goods> goodsList;
    private Context context;
    public CategoryRightAdapter(Context context, List<Goods> goodsList) {
        this.context = context;
        this.goodsList = goodsList;
    }
    @Override
    public int getCount() {
        return goodsList.size();
    }
    @Override
    public Object getItem(int position) {
        return goodsList.get(position);
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.rv_item, null);
            viewHolder = new ViewHolder(convertView);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        Goods goods = goodsList.get(position);
        viewHolder.tvProductName.setText(goods.getDbTitle());
        viewHolder.tvProductDesc.setText(goods.getDbPrice());
        return convertView;
    }
    static class ViewHolder {
        TextView tvProductName;
        TextView tvProductDesc;
    }
}

2. 购物车页面（ShoppingCarFragment.java）

package com.domain.mainView.fragment;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.domain.mainView.R;
public class ShoppingCarFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_shoppingcar, container, false);
    }
}

3. 购物车适配器（ShoppingCarAdapter.java）

package com.domain.mainView.adapter;
import android.content.Context;
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.domain.mainView.R;
import com.domain.mainView.model.Car;
import java.util.List;
public class ShoppingCarAdapter extends BaseAdapter {
    private List<Car> carList;
    private Context context;
    public ShoppingCarAdapter(Context context, List<Car> carList) {
        this.context = context;
        this.carList = carList;
    }
    @Override
    public int getCount() {
        return carList.size();
    }
    @Override
    public Object getItem(int position) {
        return carList.get(position);
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.rv_item, null);
            viewHolder = new ViewHolder(convertView);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        Car car = carList.get(position);
        viewHolder.tvProductName.setText(car.getDbTitle()); // 假设Car类有getDbTitle方法获取商品名称
        viewHolder.tvProductDesc.setText(String.valueOf(car.getDbQuantity())); // 显示商品数量
        return convertView;
    }
    static class ViewHolder {
        TextView tvProductName;
        TextView tvProductDesc;
    }
}

五、布局文件

1. 购物车布局页面（fragment_shoppingcar.xml）

<?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"
    android:orientation="vertical">
    <!-这里可以放置RecyclerView或其他控件 -->
</LinearLayout>

2. RecyclerView的list项布局（rv_item.xml）

<?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="wrap_content"
    android:orientation="horizontal">
    <!-这里可以放置商品的图片、名称、价格等信息 -->
</LinearLayout>

3. 购物车页面布局（activity_main.xml）

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <!-这里可以放置RecyclerView或其他控件 -->
</RelativeLayout>

到此，以上就是小编对于“Android添加商品到购物车”的问题就介绍到这了，希望介绍的几点解答对大家有用，有任何问题和不懂的，欢迎各位朋友在评论区讨论，给我留言。