java - getter 和 setter 在 recyclerview android 中没有按预期工作

Question

我正在从 volley post 请求中获取 json 值。我正在使用 setter 方法将这些值添加到列表中。当我在适配器 onBindViewholder() 方法中检索值并将其显示在 recyclerview 中时，结果未按预期显示:

下面的代码是指从 MainActivity.java 中的 volley 请求和响应向列表添加值:

    private ProductsPojo pojo;
    public static ProductsAdapter productsAdapter;
    private List<ProductsPojo> pojoList;

    pojo = new ProductsPojo();
    pojoList = new ArrayList<>();

StringRequest request = new StringRequest(Request.Method.POST, url, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
//            Log.d("Appet8","Products response:"+response.toString());

                try {
                   JSONObject jsonObject = new JSONObject(response);
                   JSONArray products = jsonObject.getJSONArray("products");

                   for (int i=0;i<products.length();i++) {
                       JSONObject product_object = products.getJSONObject(i);
                       String name = product_object.getString("name");
                       String price = product_object.getString("price");
                       String product_id = product_object.getString("id");
                       String sessionname = product_object.getString("sessionname");
                       String image = product_object.getString("image");
                       String categoryname = product_object.getString("categoryname");

                       pojo.setName(product_object.getString("name"));
                       pojo.setImage(product_object.getString("image"));
                       pojoList.add(pojo);

                   }
                    productsAdapter = new ProductsAdapter(pojoList,getApplicationContext());

                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
//                Toast.makeText(getApplicationContext(),error.getMessage(), Toast.LENGTH_LONG).show();
            }
        }) {
            @Override
            protected Map<String, String> getParams() {
                // Posting parameters to login url
                Map<String, String> params = new HashMap<String, String>();
                params.put("customer_id", customer_id);
                return params;
            }
        };

        AppController.getInstance().addToRequestQueue(request,tag_request);

下面的代码是指在 ProductFragment.java 中将适配器设置为 recyclerview:

private GridLayoutManager layoutManager;
private RecyclerView recyclerView;

 recyclerView = (RecyclerView) view.findViewById(R.id.productList);
    recyclerView.setHasFixedSize(true);
    layoutManager = new GridLayoutManager(getActivity().getApplicationContext(),3);
    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setItemAnimator(new DefaultItemAnimator());
    recyclerView.setAdapter(MainActivity.productsAdapter);

下面的代码引用了显示值的适配器类，ProductsAdapter.java:

public class ProductsAdapter extends RecyclerView.Adapter<ProductsAdapter.ProductsViewHolder> {

    private List<ProductsPojo> productList;
    private Context context;

    public ProductsAdapter(List<ProductsPojo> productList,Context context) {
        this.productList=productList;
        this.context = context;
    }

    @Override
    public ProductsViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.
                from(parent.getContext()).
                inflate(R.layout.products_list, parent, false);
        ProductsViewHolder holder = new ProductsViewHolder(view);
        return holder;
    }

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

        final ProductsPojo pojo = productList.get(position);
        Log.d("Appet8","Name:"+pojo.getName());

        holder.vTitle.setText(pojo.getName());

        holder.vTitle.setTypeface(MainActivity.font);

        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               pojo.setSelected(!pojo.isSelected());
               holder.itemView.setBackgroundColor(pojo.isSelected() ? Color.parseColor("#4D79CF08") : Color.parseColor("#2D6F6F6F"));

               if(pojo.isSelected()) {
                holder.selected.setVisibility(View.VISIBLE);
               } else if(!pojo.isSelected()) {
                holder.selected.setVisibility(View.GONE);
               }
            }
        });
     }

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

    public static class ProductsViewHolder extends RecyclerView.ViewHolder {

        protected TextView vTitle;
        protected ImageView image,selected;
        protected CardView product_card;

        public ProductsViewHolder(View v) {
            super(v);
            vTitle = (TextView) v.findViewById(R.id.title);
            image = (ImageView) v.findViewById(R.id.product);
            product_card = (CardView) v.findViewById(R.id.product_card);
            selected = (ImageView) v.findViewById(R.id.selected);
        }
    }

}

这是我从 volley 请求中得到的响应:

{
"products":[
        {
            "name":"Idli",
            "price":"120",
            "id":"Fi2mYuQA",
            "sessionname":"Breakfast",
            "image":"VCYwmSae2BShoshone_Falls-1200px.jpeg",
            "categoryname":"Veg"
        },
        {
            "name":"Meals123",
            "price":"200",
            "id":"bmF8Is1Y",
            "sessionname":"Dinner",
            "image":"sIe8JBFzaRstock-photo-115193575.jpg",
            "categoryname":"Non Veg"
        },
        {
            "name":"Dosa",
            "price":"100",
            "id":"e9sWHV4A",
            "sessionname":"Breakfast",
            "image":"j8nu4GpVa7Shoshone_Falls-1200px.jpeg",
            "categoryname":"Veg"
        },
        {
            "name":"Coca",
            "price":"40",
            "id":"0oJDfdCz",
            "sessionname":"Cold Drinks",
            "image":"LrkS8QpAs7Shoshone_Falls-1200px.jpeg",
            "categoryname":"Veg"
        },
        {
            "name":"ICe",
            "price":"100",
            "id":"2ykEgtSs",
            "sessionname":null,
            "image":"KtPX9C26oRShoshone_Falls-1200px.jpeg",
            "categoryname":"Veg"
        }
    ]
}

这是我得到的输出。项目名称重复。

以下代码引用 ProductsPojo.java:

public class ProductsPojo {
    public String name;
    public String image;
    private boolean isSelected = false;

    public void setName(String name) {
        this.name = name;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public String getName() {
        return name;
    }

    public String getImage() {
        return image;
    }

    public void setSelected(boolean selected) {
        isSelected = selected;
    }


    public boolean isSelected() {
        return isSelected;
    }
}

Answer 1

在我看来你只创建了一个 ProductsPojo 实例，在这里:

pojo = new ProductsPojo();

然后在循环中不断修改这个实例，然后一次又一次地将它添加到列表中。这样，您最终在列表中得到的相同项目(最后一个)与您在响应中获得的对象数量一样多。

您想要做的可能是每次都在 for 循环的开头创建一个新的 ProductsPojo，如下所示:

for (int i=0;i<products.length();i++) {
    ProductsPojo pojo = new ProductsPojo();

    JSONObject product_object = products.getJSONObject(i);
    String name = product_object.getString("name");
    String price = product_object.getString("price");
    String product_id = product_object.getString("id");
    String sessionname = product_object.getString("sessionname");
    String image = product_object.getString("image");
    String categoryname = product_object.getString("categoryname");

    pojo.setName(product_object.getString("name"));
    pojo.setImage(product_object.getString("image"));
    pojoList.add(pojo);
}