用android实现购物车功能，它可以可实现商品数量的增减、商品的删除以及总价格计算功能

实现购物车功能可以分为以下几个步骤：

1. 创建一个商品类，包含商品的名称、价格、图片等信息。

public class Product {
    private String name;
    private double price;
    private int image;

    public Product(String name, double price, int image) {
        this.name = name;
        this.price = price;
        this.image = image;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }

    public int getImage() {
        return image;
    }
}

2. 创建一个购物车类，包含商品列表和总价格。

public class ShoppingCart {
    private List<Product> productList;
    private double totalPrice;

    public ShoppingCart() {
        productList = new ArrayList<>();
        totalPrice = 0;
    }

    public List<Product> getProductList() {
        return productList;
    }

    public void setProductList(List<Product> productList) {
        this.productList = productList;
    }

    public double getTotalPrice() {
        return totalPrice;
    }

    public void setTotalPrice(double totalPrice) {
        this.totalPrice = totalPrice;
    }

    public void addProduct(Product product) {
        productList.add(product);
        totalPrice += product.getPrice();
    }

    public void removeProduct(Product product) {
        productList.remove(product);
        totalPrice -= product.getPrice();
    }
}

3. 在界面中展示商品列表，并添加增减和删除按钮。

public class MainActivity extends AppCompatActivity {
    private ListView listView;
    private TextView totalPriceTextView;
    private ShoppingCart shoppingCart;
    private ProductAdapter productAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        listView = findViewById(R.id.list_view);
        totalPriceTextView = findViewById(R.id.total_price_text_view);

        shoppingCart = new ShoppingCart();
        productAdapter = new ProductAdapter(this, shoppingCart.getProductList());
        listView.setAdapter(productAdapter);

        Button addButton = findViewById(R.id.add_button);
        addButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Product product = new Product("商品", 10.0, R.drawable.product);
                shoppingCart.addProduct(product);
                productAdapter.notifyDataSetChanged();
                totalPriceTextView.setText("总价：" + shoppingCart.getTotalPrice());
            }
        });

        Button removeButton = findViewById(R.id.remove_button);
        removeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!shoppingCart.getProductList().isEmpty()) {
                    Product product = shoppingCart.getProductList().get(0);
                    shoppingCart.removeProduct(product);
                    productAdapter.notifyDataSetChanged();
                    totalPriceTextView.setText("总价：" + shoppingCart.getTotalPrice());
                }
            }
        });
    }
}

4. 创建一个商品适配器类，用于展示商品列表。在适配器中实现商品数量的增减和商品的删除功能。

public class ProductAdapter extends BaseAdapter {
    private Context context;
    private List<Product> productList;

    public ProductAdapter(Context context, List<Product> productList) {
        this.context = context;
        this.productList = productList;
    }

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

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

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

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.product_item, parent, false);
        }

        ImageView imageView = convertView.findViewById(R.id.image_view);
        TextView nameTextView = convertView.findViewById(R.id.name_text_view);
        TextView priceTextView = convertView.findViewById(R.id.price_text_view);
        ImageButton addButton = convertView.findViewById(R.id.add_button);
        final TextView countTextView = convertView.findViewById(R.id.count_text_view);
        ImageButton removeButton = convertView.findViewById(R.id.remove_button);

        final Product product = productList.get(position);
        imageView.setImageResource(product.getImage());
        nameTextView.setText(product.getName());
        priceTextView.setText("价格：" + product.getPrice());
        countTextView.setText("数量：1");

        addButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int count = Integer.parseInt(countTextView.getText().toString()) + 1;
                countTextView.setText("数量：" + count);
                shoppingCart.setTotalPrice(shoppingCart.getTotalPrice() + product.getPrice());
                notifyDataSetChanged();
                totalPriceTextView.setText("总价：" + shoppingCart.getTotalPrice());
            }
        });

        removeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int count = Integer.parseInt(countTextView.getText().toString()) - 1;
                if (count < 1) {
                    shoppingCart.removeProduct(product);
                    productList.remove(product);
                } else {
                    countTextView.setText("数量：" + count);
                    shoppingCart.setTotalPrice(shoppingCart.getTotalPrice() - product.getPrice());
                }
                notifyDataSetChanged();
                totalPriceTextView.setText("总价：" + shoppingCart.getTotalPrice());
            }
        });

        return convertView;
    }
}

以上就是一个简单的购物车功能实现的示例。需要注意的是，实际项目中可能还需要处理一些其他的逻辑，例如商品库存不足时的提示等。