Java RecyclerView ViewHolder中的findViewById引发NullPointerException

我正在尝试使用RecyclerView显示数据。我不太清楚它为什么会因为NullPointerException而不断崩溃。我的理论是，它试图在视图本身被创建之前找到TextView

然而，以我的构造函数的方式，它不应该这样做

我已经做了几个小时了。任何帮助都将不胜感激

我的XML文件：

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    >
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_margin="10dp"
        >

        <TextView
            android:id="@+id/recycler_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="name"
            android:textColor="@color/icons" />

        <TextView
            android:id="@+id/recycler_price"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_marginRight="18dp"
            android:text="price"
            android:textColor="@color/icons"
            android:textStyle="bold"/>
        <TextView
            android:id="@+id/recycler_date"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="date"
            android:layout_below="@+id/recycler_name"
            android:textColor="@color/icons"
            android:textStyle="italic"
            android:paddingTop="3dp"
            />

    </RelativeLayout>
</android.support.v7.widget.CardView>

RecyclerView适配器：

public class ExpenseAdapter extends RecyclerView.Adapter<ExpenseAdapter.ItemViewHolder> {
    private ArrayList<Item> mExpenseList;

    public static class ItemViewHolder extends RecyclerView.ViewHolder {
        public TextView frag_name;
        public TextView frag_price;
        public TextView frag_date;


        public ItemViewHolder(@NonNull View itemView) {
            super(itemView);
            frag_name.findViewById(R.id.recycler_name);
            frag_price.findViewById(R.id.recycler_price);
            frag_date.findViewById(R.id.recycler_date);
        }
    }

    @NonNull
    @Override
    public ItemViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int i) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.expense, parent, false);
        ItemViewHolder viewHolder = new ItemViewHolder(v);
        return viewHolder;
    }

    // constructor to receive list of expenses for recycler view to process
    public ExpenseAdapter(ArrayList<Item> expenseList) {
         mExpenseList = expenseList;
    }

    @Override
    public void onBindViewHolder(@NonNull ItemViewHolder itemViewHolder, int i) {
        Item currItem = mExpenseList.get(i);

        itemViewHolder.frag_name.setText(currItem.getName());
        itemViewHolder.frag_price.setText(Integer.toString(currItem.getPrice()));
        itemViewHolder.frag_date.setText(currItem.getDatePurhase());
    }

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

---

在使用ItemViewHolder之前，需要在其中初始化视图。现在frag_name.findviewbydr.id.recycler_name将抛出NullPointerException，因为您试图使用错误的视图查看findViewById

使用此代码：

public ItemViewHolder(@NonNull View itemView) {
        super(itemView);
        frag_name = itemView.findViewById(R.id.recycler_name);
        frag_price = itemView.findViewById(R.id.recycler_price);
        frag_date = itemView.findViewById(R.id.recycler_date);
    }

---

frag_name.findviewbydr.id.recycler_name；-那不是怎么做的。它将是frag_name=itemView.findviewbydr.id.recycler_name；，类似地，对于others.TextView.findViewById是一个无意义的b null。。。请改为尝试itemViewHolder.findViewById。谢谢。现在我觉得问这些问题很愚蠢