Question

我从firebase获取列表并在列表视图中显示它，当点击删除按钮时，我可以删除firebase中的项目，但问题是调用notifydatasetchanged()，RecyclerView显示旧项目和新项目。

我需要知道如何防止RecyclerView显示旧项目以及我应该在哪里调用notifydatasetchanged()

public class CartRecyclerAdapter extends RecyclerView.Adapter<CartRecyclerAdapter.CartProductViewHolder> {

    MyCartFragment myCartFragment = new MyCartFragment();
    public  List<CartProduct> cart_list = myCartFragment.cart_list;
    public  ArrayList<CartProduct> data = new ArrayList<>();
    public CartRecyclerAdapter(List<CartProduct> cart_list) {
        this.data.clear();
        data.addAll(cart_list);
    }

    public class CartProductViewHolder extends RecyclerView.ViewHolder{
        View mView;
        TextView textView_name;
        TextView textView_quantity;
        TextView textView_price;
        TextView order_quantity;
        TextView order_price;
        ImageView imageView;
        ImageButton delete;
        public CartProductViewHolder(View itemView) {
            super(itemView);
            mView = itemView;
            textView_name = (TextView) itemView.findViewById(R.id.cproductname);
            textView_price = (TextView) itemView.findViewById(R.id.cproductprice);
            textView_quantity = (TextView) itemView.findViewById(R.id.cproductQuantity);
            order_price = (TextView) itemView.findViewById(R.id.cuserprice);
            order_quantity  = (TextView) itemView.findViewById(R.id.cuserquantity);
            imageView = (ImageView) itemView.findViewById(R.id.cproductimage);
            delete = (ImageButton) itemView.findViewById(R.id.cdeletebutton);   
            delete.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    int product_position = getAdapterPosition();
                    String pid = data.get(product_position).getId();
                    myCartFragment.removeitem(pid);
                    notifyDataSetChanged();                  
                }
            });
        }
        public void setName(String title) {
            textView_name.setText(title);
        }

        public void setQunatity(Double quantity) {
            textView_quantity.setText("Available Quantity: " + Double.toString(quantity));
        }
        public void setPrice(Double price) {
            textView_price.setText("Price: " + Double.toString(price));
        }
        public void setOrderPrice(Double cart_price) {
            order_price.setText("Price: " + Double.toString(cart_price));
        }
        public void setOrderQuantity(int cart_Quantity) {
            order_quantity.setText(Integer.toString(cart_Quantity));
        }
        public void setImage(String image) {
            Picasso.with(mView.getContext())
                    .load(image)
                    .placeholder(product)
                    .resize(1000,700)
                    .centerCrop()
                    .into(imageView);
        }
    }
    @Override
    public CartProductViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.product_cart_item, parent, false);

        return new CartProductViewHolder(itemView);
    }
    @Override
    public void onBindViewHolder(CartProductViewHolder holder, int position) {
        CartProduct cartProduct = data.get(position);
        holder.setName(cartProduct.getProductName());
        holder.setQunatity(cartProduct.getQuantity());
        holder.setPrice(cartProduct.getPrice());
        holder.setImage(cartProduct.getUri());
        holder.setOrderQuantity(cartProduct.getCart_quantity());
        holder.setOrderPrice(cartProduct.getCart_price());
    }
    @Override
    public int getItemCount() {
        return data.size();
    }
}

Answer 1

您还必须从ArrayList中删除数据

delete.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            int product_position = getAdapterPosition();
            String pid = data.get(product_position).getId();
            myCartFragment.removeitem(pid);
            data.remove(product_position);
            notifyDataSetChanged();                  
        }
    });

Answer 2

您可以使用适配器中的新数据创建一种删除旧数据的方法：

public class CartRecyclerAdapter extends RecyclerView.Adapter<CartRecyclerAdapter.CartProductViewHolder> {

  ...

  public void swap(List<CartProduct> cartList) {
    data.clear();
    data.addAll(cartList);
    notifyDataSetChanged();
  }

}

然后，您可以调用它来更新列表：

yourAdapter.swap(cartList);

请检查以下代码是否有错误：

public class CartRecyclerAdapter extends RecyclerView.Adapter<CartRecyclerAdapter.CartProductViewHolder> {

    MyCartFragment myCartFragment = new MyCartFragment();
    public  List<CartProduct> cart_list = myCartFragment.cart_list;

    ...
}

在myCartFragment实例化的地方，然后您尝试获取CartProduct的列表。由于创建片段的异步过程，myCartFragment尚未完成，因此会在代码中引入错误。

调用notifydatasetchanged（）时，适配器也会显示旧列表项以及新项

2 个答案: