增加和减少项目的数量并通知 RecyclerView 不工作

Question

我遇到了 RecyclerView 的问题。
我需要在 onBindViewHolder() 中绑定 TextView，因此数量值会保存在项目的位置上。
问题是：如果我向下滚动，第 1 项的数量出现在第 8 项，当我向后滚动时，它出现在第 2 项。或者如果我增加位置 3 的数量并在位置 0 输入新产品，数量保持在相同的位置，而不是在项目位置。我知道视图会被回收，我应该调用按钮点击 notifiyItemChanged(getAdapterposition()); 或 notifiyDataSetChanged(); 但它不起作用。

（notifyDataSetchanged(); 做了一些奇怪的事情。当我单击第 2 项的增量按钮时，它会增加第 1 项的数量，并且在滚动时它也会被回收（数量改变位置））

这是我需要的类似帖子：
set text in textview of a list item on click of button（来自 ataulm 的回答）我需要这个用于 RecyclerView。
希望有人可以帮助我，这真的很令人沮丧。提前致谢！

ProductList.java

public class ProductList extends Fragment implements AdapterView.OnItemClickListener {

    private RecyclerView recyclerView;
    private RecyclerView.Adapter rvAdapter;
    private RecyclerView.LayoutManager rvLayoutManager;
    static ArrayList items;
    private EditText productInput;
    private TextView productQuantity;


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View productView = inflater.inflate(R.layout.item_list, container, false);


        items = new ArrayList<>();
        // 13 items
        items.addAll(Arrays.asList("Wheels", "Oil", "Water", "Wax", "Paint",
                "Detergents", "Foil", "Hub Caps", "Sponge", "Brake Fluid", "Little Trees", "First Aid Boxes", "Antifreeze"));

        recyclerView = (RecyclerView) productView.findViewById(R.id.recylcerview_list);
        recyclerView.setHasFixedSize(true);
        rvLayoutManager = new LinearLayoutManager(getActivity());
        recyclerView.setLayoutManager(rvLayoutManager);

        rvAdapter = new RvAdapterClass();
        recyclerView.setAdapter(rvAdapter);
        recyclerView.setItemAnimator(null);

        final Handler handler = new Handler();
        productInput = (EditText) productView.findViewById(R.id.item_input);

        productInput.setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event) {
                if (productInput.getText().length() > 0 && (event.getAction() == KeyEvent.ACTION_DOWN) &&
                        (keyCode == KeyEvent.KEYCODE_ENTER)) {
                    // Perform action on key press
                    String newProduct = productInput.getText().toString();
                    items.add(0, newProduct);
                    rvAdapter.notifyDataSetChanged();
                    productInput.setText(null);

                    // After Keypress down focus gets back to EditText
                    handler.postDelayed(new Runnable() {
                        @Override
                        public void run() {
                            productInput.setFocusableInTouchMode(true);
                            productInput.setFocusable(true);
                            productInput.requestFocus();
                        }
                    }, 200);

                    return true;
                }

                return false;
            }
        });

        return productView;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);


    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    }

}

RvAdapterClass.java

public class RvAdapterClass extends RecyclerView.Adapter<RvAdapterClass.ViewHolderClass> {


    public class ViewHolderClass extends RecyclerView.ViewHolder implements View.OnClickListener {
        TextView productName, productQuantity;
        Button decrementBtn, incrementBtn;


        public ViewHolderClass(View itemView) {
            super(itemView);
            productName = (TextView) itemView.findViewById(R.id.item_name);
            productQuantity = (TextView) itemView.findViewById(R.id.quantity_field);

            decrementBtn = (Button) itemView.findViewById(R.id.decrement_btn);
            decrementBtn.setOnClickListener(this);

            incrementBtn = (Button) itemView.findViewById(R.id.increment_btn);
            incrementBtn.setOnClickListener(this);

        }

        @Override
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.increment_btn:
                    int i = Integer.parseInt(productQuantity.getText().toString());
                    i++;
                    productQuantity.setText(String.valueOf(i));
                    notifyItemChanged(getAdapterPosition());
                    break;
                case R.id.decrement_btn:
                    i = Integer.parseInt(productQuantity.getText().toString());
                    i--;
                    productQuantity.setText(String.valueOf(i));
                    notifyItemChanged(getAdapterPosition());
                    break;
            }

        }


    }

    private View.OnClickListener onClickListener = new View.OnClickListener() {
        @Override
        public void onClick(final View v) {

        }
    };


    @Override
    public ViewHolderClass onCreateViewHolder(ViewGroup parent, int viewType) {
        View productItem = LayoutInflater.from(parent.getContext()).inflate(R.layout.single_item, parent, false);
        return new ViewHolderClass(productItem);

    }

    @Override
    public void onBindViewHolder(final ViewHolderClass holder, final int position) {
        holder.productName.setText(String.valueOf(ProductList.items.get(position)));

//        Here is soemthing needed to bind the product quantity
//        holder.productquantity.setText("" + getQuantity(holder); isn't working because quantity doesn't change!! 


    }

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

    private void removeItem(int position) {
        ProductList.items.remove(position);
        notifyItemRemoved(position);
    }

    public int getQuantity(final ViewHolderClass holder) {
        return Integer.parseInt(holder.productQuantity.getText().toString());
    }

}

item_list.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:paddingLeft="8dp"
    android:paddingRight="8dp">


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="65dp"
        android:focusable="true"
        android:focusableInTouchMode="true"
        android:gravity="center"
        android:orientation="horizontal"
        android:paddingRight="31dp">

        <EditText
            android:id="@+id/item_input"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="item"
            android:inputType="textCapWords"
            android:maxLines="1"
            android:singleLine="true" />
    </LinearLayout>


    <android.support.v7.widget.RecyclerView
        android:id="@+id/recylcerview_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scrollbarAlwaysDrawVerticalTrack="true"
        android:scrollbars="vertical"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />


</LinearLayout>

Answer 1

所以基本上你是在维护一个项目列表及其数量。首先在片段中使用静态项目列表是不好的。而是在适配器构造函数中传递它。其次将其更改为类。关键是项目，价值是数量。

Class Item{
String itemType;
int quantity;
}

    RvAdapterClass(ArrayList<Item> items){
    this.items = items;
    }

现在从列表中获取对象并访问值。此外，当增加或减少数量时，更新此列表中相应对象中的值。

 @Override 
    public void onBindViewHolder(final ViewHolderClass holder, final int position) {
        holder.productName.setText(items.get(position).itemType);

//        Here is soemthing needed to bind the product quantity 
      holder.productquantity.setText("" + items.get(position).quantity);  

    } 

问题在于视图的回收。

Answer 2

尝试以下方法：

在 ProductList 类中创建片段的 onresume()。

还有实现

  rvAdapter.notifyDataSetChanged();