<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:background="@color/transparent"
    android:layout_height="wrap_content">

    <androidx.cardview.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:cardUseCompatPadding="true"
        app:cardCornerRadius="6dp"
        app:cardElevation="5dp">

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <ImageView
                android:id="@+id/comPreview"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerInParent="true"
                android:adjustViewBounds="true"
                android:src="@mipmap/test" />

            <TextView
                android:id="@+id/comName"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@id/comPreview"
                android:layout_marginTop="20dp"
                android:layout_marginBottom="5dp"
                android:text="标题"
                android:textColor="@color/black"
                android:textSize="20sp" />

            <TextView
                android:id="@+id/comPrice"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@id/comName"
                android:text="￥0.0"
                android:textColor="@color/red" />

            <TextView
                android:id="@+id/paidNum"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@id/comName"
                android:layout_marginLeft="5dp"
                android:layout_toRightOf="@id/comPrice"
                android:text="0人付款" />

            <TextView
                android:id="@+id/comStock"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@id/comName"
                android:layout_alignParentRight="true"
                android:text="库存10000" />
        </RelativeLayout>

    </androidx.cardview.widget.CardView>

</RelativeLayout>

public class CategoryPagerPresenterImpl implements ICategoryPagerPresenter {
    
    private Map<String, Integer> pageInfo = new HashMap<>();
    private static final int DEFAULT_PAGE = 1;

    private CategoryPagerPresenterImpl(){}

    private static ICategoryPagerPresenter sInstance = null;

    public static ICategoryPagerPresenter getInstance(){
        if (sInstance == null) {
            sInstance = new CategoryPagerPresenterImpl();
        }
        return sInstance;
    }

    @Override
    public void getContentByCategory(String categoryTitle, int categoryId) {

        for (ICategoryPagerCallback callback : callbacks) {
            if (callback.getCategoryId() == categoryId) {
                callback.onLoading();
            }
        }
        //根据分类加载内容
        Retrofit retrofit = RetrofitManager.getInstance().getRetrofit();
        Api api = retrofit.create(Api.class);
        Integer targetPage = pageInfo.get(categoryTitle);
        if (targetPage == null) {
            targetPage = DEFAULT_PAGE;
            pageInfo.put(categoryTitle, targetPage);
        }
        String shopPagerUrl = UrlUtils.createShopPagerUrl(categoryTitle);
        LogUtils.d(CategoryPagerPresenterImpl.this, "shop pager url --> " + shopPagerUrl);

        Call<Commodities> task = api.getCommoditiesByCategory(shopPagerUrl);
        task.enqueue(new Callback<Commodities>() {
            @Override
            public void onResponse(Call<Commodities> call, Response<Commodities> response) {
                int code = response.code();
                LogUtils.d(CategoryPagerPresenterImpl.this, "code --> " + code);
                if (code == HttpURLConnection.HTTP_OK) {
                    Commodities commodities = response.body();
                    LogUtils.d(CategoryPagerPresenterImpl.this, "commodities --> " + commodities.toString());
                    //更新UI
                    handleShopPagerContentResult(commodities, categoryId);
                } else {
                    handlerNetworkError(categoryId);
                }
            }
            @Override
            public void onFailure(Call<Commodities> call, Throwable t) {
                LogUtils.d(CategoryPagerPresenterImpl.this, "onFailure --> " + t.toString());
            }
        });
    }

    private void handlerNetworkError(int categoryId) {
        for (ICategoryPagerCallback callback : callbacks){
            if (callback.getCategoryId() == categoryId) {
                callback.onError();
            }
        }
    }

    /**
     * 通知UI更新
     * @param commodities
     * @param categoryId
     */
    private void handleShopPagerContentResult(Commodities commodities, int categoryId) {
        for (ICategoryPagerCallback callback : callbacks){
            if (callback.getCategoryId() == categoryId) {
                if (commodities == null || commodities.getData().size() == 0) {
                    callback.onEmpty();
                } else {
                    callback.onContentLoaded(commodities.getData());
                }
            }
        }
    }

    private ArrayList<ICategoryPagerCallback> callbacks = new ArrayList<>();
    @Override
    public void registerCallback(ICategoryPagerCallback callback) {
        if (!callbacks.contains(callback)) {
            callbacks.add(callback);
        }

    }

    @Override
    public void unregisterCallback(ICategoryPagerCallback callback) {
        callbacks.remove(callback);
    }
}

public class ShopPagerContentAdapter extends RecyclerView.Adapter<ShopPagerContentAdapter.InnerHolder> {

    List<Commodities.DataBean> mData = new ArrayList<>();

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

    @Override
    public void onBindViewHolder(@NonNull InnerHolder holder, int position) {
        Commodities.DataBean dataBean = mData.get(position);
        holder.setData(dataBean);
    }

    @Override
    public int getItemCount() {
        if (mData != null) {
            return mData.size();
        }
        return 0;
    }

    public void setCommodities(List<Commodities.DataBean> commodities) {
        mData.clear();
        mData.addAll(commodities);
        notifyDataSetChanged();
    }

    public class InnerHolder extends RecyclerView.ViewHolder {

        @BindView(R.id.comName)
        public TextView comName;
        @BindView(R.id.comPrice)
        public TextView comPrice;
        @BindView(R.id.comStock)
        public TextView comStock;
        @BindView(R.id.paidNum)
        public TextView paidNum;
        @BindView(R.id.comPreview)
        public ImageView comPreview;

        //找到条目控件
        public InnerHolder(@NonNull View itemView) {
            super(itemView);
            ButterKnife.bind(this, itemView);
        }

        public void setData(Commodities.DataBean dataBean) {
            comName.setText(dataBean.getComName());
            comPrice.setText("￥"+dataBean.getComPrice());
            comStock.setText("库存"+dataBean.getComStock());
            paidNum.setText(dataBean.getPaidNum()+"人付款");
            Glide.with(itemView.getContext()).load(dataBean.getComPreview()).into(comPreview);

        }
    }
}

失效，应该是写布局有问题。但是没代码，不好分析

问题1 ：失效 找不到指定id 或者你这个id在你这个view的下面（相对布局有顺序的）

属性具体查看：https://www.runoob.com/w3cnote/android-tutorial-relativelayout.html

问题2： 是不是数据太少了 没太懂 就像康师傅说的 要代码看看

上代码