Question

我有一个RecylcerView，它显示存储在SQLite中的项目列表。

每行上都有一个向上和按钮，单击时可以增加/减少金额。假设我点击了ABCD行上的向下按钮，那么金额文本将更改为“金额：1”

到目前为止，这是我的代码：

ItemAdapter.java

public class ItemAdapter extends RecyclerView.Adapter<ItemAdapter.MyViewHolder> {

    private List<Itemt> itemList;
    private Context ctxt;
    private MyClickListener clickListener;

    public ItemAdapter(Context ctxt, List<Item> list, MyClickListener listener){
        this.ctxt = ctxt;
        this.itemtList = list;
        this.clickListener = listener;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int type) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.list_row, parent, false);

        return new ItemAdapter.MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        Item item = itemtList.get(position);
    holder.tvName.setText(item.getName());
    holder.tvPrice.setText(item.getPrice());
    holder.tvAmount.setText("Amount: "+ item.getAmount());
    }

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

    class MyViewHolder extends RecyclerView.ViewHolder {

        public TextView tvNama, tvHargaJual, tvHargaBeli, tvJumlah;
        public Button btnInc, btnDec;
        MyClickListener listener;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            tvName = itemView.findViewById(R.id.tv_name);
            tvPrice = itemView.findViewById(R.id.tv_price);
            tvAmount = itemView.findViewById(R.id.tv_amount);
            btnInc = itemView.findViewById(R.id.btn_inc);
            btnDec = itemView.findViewById(R.id.btn_dec);

            btnInc.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    clickListener.onIncrement(view, getAdapterPosition());
                }
            });

            btnDec.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    clickListener.onDecrement(view, getAdapterPosition());
                }
            });
        }
    }

    public interface MyClickListener {
        void onIncrement(View v, int position);
        void onDecrement(View v, int position);
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    RecyclerView recView
    DBHelper db;
    List<Item> itemList;
    Item item;

     protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recView = (RecyclerView) findViewById(R.id.recycler_view);
        itemtList = new ArrayList<>();

        db = new DBHelper(this);
        itemList.addAll(db.getAllItems()); // load all stored items in SQLite db

        mAdapter = new ProductAdapter(this, productList, new ProductAdapter.MyClickListener() {
            @Override
            public void onIncrement(View v, int position) {
                item = itemList.get(position);
            }

            @Override
            public void onDecrement(View v, int position) {
            item = itemList.get(position);
            }
        });

        }
    }

当前问题是单击向上/向下按钮时，它不能修改金额文本。该如何纠正？

Answer 1

您应该在btn.setOnClickListener()中进行操作，而不是在MyViewHolder类中进行操作onBindViewHolder()。

访问如下所示的元素：

@Override
  public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
    Item item = itemtList.get(position);
    holder.tvName.setText(item.getName());
    holder.tvPrice.setText(item.getPrice());
    holder.tvAmount.setText("Amount: "+ item.getAmount());

    holder.btnInc.setOnClickListener(
       //do ur stuff here
     )
    holder.btnInc.setOnClickListener(
       //do ur another stuff here
      )
}

同时删除onClickListener()类中按钮的MyViewHolder。因为MyViewHolder只是您查找所有UI元素的地方。该操作在onBindViewHolder()

中完成

Answer 2

首先，必须在amount和onIncrement方法中更改onDecrement的值。像这样的东西：

item = itemList.get(position);
itme.setAmount(item.getAmount()++);
----------------------------------------------
item = itemList.get(position);
itme.setAmount(item.getAmount()--);

，然后您必须通知recyclerView适配器该代码更改了数据：

 mAdapter.notifyDataSetChanged();

所有代码都一起放在这里：

mAdapter = new ProductAdapter(this, productList, new ProductAdapter.MyClickListener() {
        @Override
        public void onIncrement(View v, int position) {
            item = itemList.get(position);
            itme.setAmount(item.getAmount()++);
            mAdapter.notifyDataSetChanged();
        }

        @Override
        public void onDecrement(View v, int position) {
            item = itemList.get(position);
            itme.setAmount(item.getAmount()--);
            mAdapter.notifyDataSetChanged();
        }
    });

Answer 3

只需更改项目数量，然后调用mAdapter.notifyItemChanged（position），示例：

mAdapter = new ProductAdapter(this, productList, new ProductAdapter.MyClickListener() {
                @Override
                public void onIncrement(View v, int position) {
                    item = itemList.get(position);
                    item.setAmount(item.getAmount()++);
                    mAdapter.notifyItemChanged(position);
                }

                @Override
                public void onDecrement(View v, int position) {
                item = itemList.get(position);
                item.setAmount(item.getAmount()--);
                mAdapter.notifyItemChanged(position);
                }
            });

如何在RecyclerView内部处理点击以更新UI？

3 个答案: