java - android:如何增加购物车中商品的数量

Question

当用户多次在购物车中添加相同的商品时，应该仅添加该商品一次并增加该商品的数量，但在我的情况下，每次都会添加整个商品。

以下是购物车 Activity :

public class CartActivity extends AppCompatActivity implements CartAdapter.OnCartDataChangeListener {


    DatabaseHandler helper;
    public static List<ProductModel> dbList;
    RecyclerView mRecyclerView;
    Toolbar toolbar;
    Button btnCheckout, btnContinueShopping;
    public TextView tvTotalNoOfItems, tvTotalPrice;
    String productVaiantId;
    String selectedProductId;

    private RecyclerView.Adapter mAdapter;
    private LinearLayoutManager mLayoutManager;


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

        productVaiantId = getIntent().getStringExtra("variant_id");
        selectedProductId = getIntent().getStringExtra("product_id");
        Bundle extras = getIntent().getExtras();
        if (extras != null) {
            productVaiantId = extras.getString("variant_id");
            selectedProductId = extras.getString("product_id");
        }

        toolbar = (Toolbar) findViewById(R.id.customToolBar);
        setSupportActionBar(toolbar);
        setTitle("Check-out");
        toolbar.setTitleTextColor(Color.BLACK);

        toolbar.setNavigationIcon(R.drawable.ic_arrow_back_black);
        toolbar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onBackPressed();
            }
        });

        helper = new DatabaseHandler(this);
        dbList = new ArrayList<ProductModel>();
        dbList = helper.getDataFromDB();

        mRecyclerView = (RecyclerView) findViewById(R.id.rv_cart_item_list);

        // use a linear layout manager
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);


        mLayoutManager = new LinearLayoutManager(this) {

            @Override
            public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
                LinearSmoothScroller smoothScroller = new LinearSmoothScroller(CartActivity.this) {

                    private static final float SPEED = 300f;// Change this value (default=25f)

                    @Override
                    protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
                        return SPEED / displayMetrics.densityDpi;
                    }

                };
                smoothScroller.setTargetPosition(position);
                startSmoothScroll(smoothScroller);
            }

        };
        mAdapter = new CartAdapter(this, dbList, this);

        tvTotalNoOfItems = (TextView) findViewById(R.id.tvTotalCartItems);
        tvTotalPrice = (TextView) findViewById(R.id.tvTotalCartItemsPrice);

        tvTotalNoOfItems.setText(dbList.size() + "");
        double totalPrice = 0.0;
        for (int i = 0; i < dbList.size(); i++) {
            totalPrice += Double.parseDouble(dbList.get(i).getPrice());
        }
        tvTotalPrice.setText("" + totalPrice);

        mRecyclerView.setAdapter(mAdapter);
        mRecyclerView.setItemAnimator(new SlideInUpAnimator());

        btnContinueShopping = (Button) findViewById(R.id.btnBackToProductActivity);
        btnContinueShopping.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent launchCollectionActivity = new Intent(CartActivity.this, CollectionActivity.class);
                startActivity(launchCollectionActivity);
                finish();
            }
        });

        btnCheckout = (Button) findViewById(R.id.btn_checkout);
        btnCheckout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mAdapter.getItemCount() == 0){
                    Toast.makeText(CartActivity.this,"Your cart is empty",Toast.LENGTH_SHORT).show();
                }
                else {
                    Intent launchCheckoutActivity = new Intent(CartActivity.this, CheckoutActivity.class);
                    startActivity(launchCheckoutActivity);
                } }
        });
    }

  @Override
    public void dataChanged() {

        tvTotalNoOfItems.setText(dbList.size() + "");
        double totalPrice = 0.0;
        for (int i = 0; i < dbList.size(); i++) {
            totalPrice += Double.parseDouble(dbList.get(i).getPrice());
        }
        tvTotalPrice.setText("" + totalPrice);
}
}

下面是购物车适配器:

public class CartAdapter extends RecyclerView.Adapter<CartAdapter.ViewHolder> {

    public interface OnCartDataChangeListener{
        public void dataChanged();
    }
    private OnCartDataChangeListener listener;

    private List<ProductView.Data> productData = Collections.emptyList();
    static List<ProductModel> productModelList;
    static  Context context;
    DatabaseHandler mDatabaseHandler;

    public CartAdapter(Context context, List<ProductModel> dbList, OnCartDataChangeListener listener ){
        this.productModelList = new ArrayList<ProductModel>();
        this.context = context;
        this.productModelList = dbList;
        mDatabaseHandler = new DatabaseHandler( context );
        this.listener = listener;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        Context context = parent.getContext();
        LayoutInflater inflater = LayoutInflater.from(context);

        // Inflate the custom layout
        View cartListView = inflater.inflate(R.layout.list_item_cart, parent, false);

        // Return a new holder instance
        ViewHolder viewHolder = new ViewHolder(context,cartListView);
        return viewHolder;

    }

    @Override
    public void onBindViewHolder(ViewHolder holder, final int position) {

        holder.tvProductName.setText(productModelList.get(position).getTitle());
        holder.tvProductPrice.setText(productModelList.get(position).getPrice());
        Glide
                .with(context)
                .load(productModelList.get(position).getImageUrl())
                .placeholder(R.drawable.placeholder_loading)
                .into(holder.imgProduct);

        holder.tvSize.setText(productModelList.get(position).getSize());
        holder.tvProductQuantity.setText(Integer.toString(productModelList.get(position).getQuantity()));
        holder.tvColor.setText(productModelList.get(position).getColor());


        holder.imgDelete.setClickable(true);
        holder.imgDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String idForDelete = String.valueOf(productModelList.get(position).getVariantId());

                mDatabaseHandler.deleteARow(idForDelete);
                productModelList.remove(position);
                notifyItemRemoved(position);
                notifyItemRangeChanged(position,productModelList.size());

                CartActivity.dbList = productModelList;
                listener.dataChanged();
            }
        });

    }

    @Override
    public int getItemCount() {

        return productModelList.size();
    }

    public void Refresh(ArrayList<ProductModel> datas) {
        this.productModelList.clear();
        this.productModelList.addAll(datas);
        notifyDataSetChanged();
    }




    public class ViewHolder extends RecyclerView.ViewHolder {

        TextView tvProductName, tvProductPrice, tvProductQuantity, tvColor,
                tvSize;
        ImageView imgProduct;
        ImageButton imgDelete;
        Context context;

        public ViewHolder(Context mContext, View itemView) {
            super(itemView);

            this.tvProductName = (TextView) itemView.findViewById(R.id.tv_cart_product_name);
            this.tvProductPrice = (TextView) itemView.findViewById(R.id.tv_cart_product_price);
            this.tvProductQuantity = (TextView) itemView.findViewById(R.id.tv_cart_product_Quantity);
            this.imgProduct = (ImageView) itemView.findViewById(R.id.img_cart_item_product);
            this.tvColor = (TextView) itemView.findViewById(R.id.tv_color);
            this.tvSize = (TextView) itemView.findViewById(R.id.tv_size);
            this.imgDelete = (ImageButton) itemView.findViewById(R.id.img_cart_delete);
            //  store the context ///
            this.context = mContext;

        }

    }

此 fragment 来 self 在按下 addToCart 按钮时获取产品的先前 Activity :

 btn_addToCart.setOnClickListener(new View.OnClickListener() {
                                    @Override
                                    public void onClick(View view) {
                                        String title = tv_productName.getText().toString();
                                        String price = tv_productPrice.getText().toString();
                                        String status = tv_productStatus.getText().toString();
                                        String imageUrl = productImageList.get(0);
                                        String productColor = String.valueOf(sp_productColor.getSelectedItem());
                                        String productSize = String.valueOf(sp_productSize.getSelectedItem());
                                        String productQuantity = String.valueOf(tv_productQuantity.getText());

                                        final String productId = response.data().node().asProduct().id();
                                        final String variantId = response.data().node().asProduct().variants().edges().get(0).node().id();

                                        // save into database
                                        helper = new DatabaseHandler(ProductDetailActivity.this);
                                        helper.insertIntoDB(variantId, title, price, imageUrl, status, productSize, productQuantity, productColor);

                                        // display snackbar to navigate to cart activity
                                        Snackbar.make(view, R.string.snackbar_text, Snackbar.LENGTH_LONG)
                                                .setAction(R.string.snackbar_action, new View.OnClickListener() {
                                                    @Override
                                                    public void onClick(View v) {

                                                        Intent launchCartActivity = new Intent(ProductDetailActivity.this, CartActivity.class);
                                                        // adding the first product and its first variant to the cart
                                                         launchCartActivity.putExtra("product_id", productId);
                                                        launchCartActivity.putExtra("variant_id", variantId);
                                                       startActivity(launchCartActivity);
                                                        finish();
                                                    }
                                                }).show();
                                    }
                                });

Answer 1

您应该申请支票。如果购物车中已存在该商品，则只需增加数量像这样尝试一下。

private boolean isAlreadyInCart(int targetItemId) {
    boolean isAlreadyInCart = false;
    for (int i = 0; i < itemIds.length; i++) {
        if (targetItemId == itemIds[i]) {
            isAlreadyInCart = true;
            break;
        }
    }
    return isAlreadyInCart;
}

现在像这样调用使用这个方法。

if (!isAlreadyInCart(itemId)) {
    // TODO: add item to cart
} else {
    // TODO: increase quantity
}