Android studio实现简单购物车加减商品结算

实现简单购物车加减商品结算，可以按照以下步骤进行：

1. 创建一个商品类，包含商品名称、商品价格、商品数量等属性。

public class Goods {
    private String name;
    private double price;
    private int quantity;

    public Goods(String name, double price, int quantity) {
        this.name = name;
        this.price = price;
        this.quantity = quantity;
    }

    // getter和setter方法
}

2. 在Activity中创建一个列表，用于展示购物车中的商品。

List<Goods> goodsList = new ArrayList<>();

3. 创建一个适配器，将商品列表展示到RecyclerView中。

public class GoodsAdapter extends RecyclerView.Adapter<GoodsAdapter.ViewHolder> {
    private List<Goods> mGoodsList;

    static class ViewHolder extends RecyclerView.ViewHolder {
        TextView goodsName;
        TextView goodsPrice;
        TextView goodsQuantity;

        public ViewHolder(View view) {
            super(view);
            goodsName = view.findViewById(R.id.goods_name);
            goodsPrice = view.findViewById(R.id.goods_price);
            goodsQuantity = view.findViewById(R.id.goods_quantity);
        }
    }

    public GoodsAdapter(List<Goods> goodsList) {
        mGoodsList = goodsList;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.goods_item, parent, false);
        ViewHolder holder = new ViewHolder(view);
        return holder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        Goods goods = mGoodsList.get(position);
        holder.goodsName.setText(goods.getName());
        holder.goodsPrice.setText(String.valueOf(goods.getPrice()));
        holder.goodsQuantity.setText(String.valueOf(goods.getQuantity()));
    }

    @Override
    public int getItemCount() {
        return mGoodsList.size();
    }
}

4. 在布局文件中添加RecyclerView和结算按钮。

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/goods_list"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="16dp" />

<Button
    android:id="@+id/checkout_button"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="16dp"
    android:text="结算" />

5. 在Activity中初始化RecyclerView和适配器。

RecyclerView recyclerView = findViewById(R.id.goods_list);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
GoodsAdapter adapter = new GoodsAdapter(goodsList);
recyclerView.setAdapter(adapter);

6. 添加添加商品和删除商品的功能。

// 添加商品
goodsList.add(new Goods("商品1", 10.0, 1));
adapter.notifyDataSetChanged();

// 删除商品
goodsList.remove(position);
adapter.notifyItemRemoved(position);

7. 添加加减商品数量的功能。

// 商品数量加1
goods.setQuantity(goods.getQuantity() + 1);
adapter.notifyItemChanged(position);

// 商品数量减1
if (goods.getQuantity() > 0) {
    goods.setQuantity(goods.getQuantity() - 1);
    adapter.notifyItemChanged(position);
}

8. 添加结算功能。

double totalPrice = 0;
for (Goods goods : goodsList) {
    totalPrice += goods.getPrice() * goods.getQuantity();
}
Toast.makeText(this, "总价为：" + totalPrice, Toast.LENGTH_SHORT).show();

这样，一个简单的购物车加减商品结算就实现了。