Cart 关于购物车里面需要封装的方法

对购物车进行增删改之后，都需要保存数据 saveCart();

//购物车需要当作对象 传递，要实现序列化接口Serializable
public class Cart implements Serializable {
//购物车里面的购物项集合
    private List<CartItem> items = new ArrayList<CartItem>();

    public List<CartItem> getItems() {
        return this.items;
    }

    /** * 修改图书的数量 * * @param num */
    public void modifyNum(int id, int num) {
        Log.i("info","隐形了modifyNum方法:["+id+","+num+"]");
        for (CartItem item : items) {
            if (item.getBook().getId()==id) {
                item.setCount(num);
                saveCart();
                return;
            }
        }
    }

    /** * 移除购物项 * */
    public void deleteBook(int id) {
        for (CartItem item : items) {
            if (item.getBook().getId()==id) {
                items.remove(item);
                return;
            }
        }
        saveCart();
    }

    /** * 购买 * * @param book */
    public boolean buy(Book book) {
        for (int i = 0; i < items.size(); i++) {
            CartItem item = items.get(i);
            if (item.getBook().equals(book)) {
                item.setCount(item.getCount() + 1);
                return false;
            }
        }
        //没有添加过
        CartItem item = new CartItem(book, 1);
        items.add(item);
        saveCart();
        return true;
    }
//GlobalConsts.CART_CACHE_FILE_NAME);
//public static final String CART_CACHE_FILE_NAME="CART.INFO";
    /** * 持久化到文件中 下次打开应用购物车依然存在 */
    public void saveCart() {
        try {
            File file = new File(MyApplication.getContext().getCacheDir(), GlobalConsts.CART_CACHE_FILE_NAME);
            ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file));
            oos.writeObject(this);
            oos.flush();
            oos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    /** * 从序列化的文件中读取购物车信息 * * @return */
    public Cart readCart() {
        try {
            File file = new File(MyApplication.getContext().getCacheDir(), GlobalConsts.CART_CACHE_FILE_NAME);
            ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file));
            Cart cart = (Cart) ois.readObject();
            if(cart == null){
                return new Cart();
            }
            return cart;
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return new Cart();
    }

    @Override
    public String toString() {
        return "Cart{" +
                        "items=" + items +
                        '}';
    }

    /** * 1,1;2,3;4,1 */
    public String CartToString() {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < items.size(); i++) {
            CartItem c = items.get(i);
            sb.append(c.getBook().getId());
            sb.append(","+c.getCount()+";");
        }
        sb.deleteCharAt(sb.length()-1);
        return sb.toString();
    }
//获得购物车所有购物项的总价
    public double getTotalPrice() {
        double price = 0;
        for(CartItem item:items){
            price += item.getBook().getDangPrice()*item.getCount();
        }
        return price;
    }
}