android：如何增加购物车中物品的数量

问题描述：

当用户在购物车中多次添加同一物品多次时，应该只将该物品添加一次，并增加该物品的数量，但在我的情况下整个项目每次都添加。android：如何增加购物车中物品的数量

下面

是车活动：

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; 

     } 

    }

这片段是从以前的活动从当按下addToCart按钮我得到的产品：

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(); 
            } 
           });

请分享您的代码？你在哪里得到错误？ –

您的代码存在问题。 –

检查列表中存在的产品ID是否存在增加数量 –

答

您应该申请支票。如果该商品已经存在于购物车中，那么只能增加数量请尝试这样。

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

现在调用这个方法。

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

android：如何增加购物车中物品的数量

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