OnClickListener在RecyclerView AdapterClass

Question

我正在使用CardView和RecyclerView。当我添加此行“ listener.onCardSelected（position，holder.thumbnail）;”时在侦听器中，我得到了错误。如果我在这行上打断我的项目，请运行。但是我需要这条线，而且我找不到它的固定方式， 抱歉，我的英语

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

private Context mContext;
private List<Album> albumList;
private AlbumsAdapterListener listener;

public class MyViewHolder extends RecyclerView.ViewHolder {
    public TextView title, count;
    public ImageView thumbnail, overflow;
    public CardView cardView;

    public MyViewHolder(View view) {
        super(view);
        title = view.findViewById(R.id.title);
        count = view.findViewById(R.id.count);
        thumbnail = view.findViewById(R.id.thumbnail);
        overflow = view.findViewById(R.id.overflow);
        cardView = view.findViewById(R.id.card_view);
    }
}


public AlbumsAdapter(Context mContext, List<Album> albumList, AlbumsAdapterListener listener) {
    this.mContext = mContext;
    this.albumList = albumList;
    this.listener = listener;
}

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

    return new MyViewHolder(itemView);
}

@Override
public void onBindViewHolder(final MyViewHolder holder, final int position) {
    Album album = albumList.get(position);
    holder.title.setText(album.getName());
    holder.count.setText(album.getNumOfSongs() + " songs");

    /*loading album cover using Glide library*/
    Glide.with(mContext).load(album.getThumbnail()).into(holder.thumbnail);

    holder.overflow.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            showPopupMenu(holder.overflow, position);
        }
    });

    holder.cardView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            listener.onCardSelected(position, holder.thumbnail);
        }
    });

    holder.thumbnail.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            listener.onCardSelected(position, holder.thumbnail);
        }
    });
}

/**
 * Showing popup menu when tapping on 3 dots
 */
private void showPopupMenu(View view, int position) {

    PopupMenu popup = new PopupMenu(mContext, view);
    MenuInflater inflater = popup.getMenuInflater();
    inflater.inflate(R.menu.menu_album, popup.getMenu());
    popup.setOnMenuItemClickListener(new MyMenuItemClickListener(position));
    popup.show();
}

/**
 * Click listener for popup menu items
 */
class MyMenuItemClickListener implements PopupMenu.OnMenuItemClickListener {

    int position;

    public MyMenuItemClickListener(int position) {
        this.position = position;
    }

    @Override
    public boolean onMenuItemClick(MenuItem menuItem) {
        switch (menuItem.getItemId()) {
            case R.id.action_add_favourite:
                listener.onAddToFavoriteSelected(position);
                return true;
            case R.id.action_play_next:
                listener.onPlayNextSelected(position);
                return true;
            default:
        }
        return false;
    }
}

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

public interface AlbumsAdapterListener {
    void onAddToFavoriteSelected(int position);

    void onPlayNextSelected(int position);

    void onCardSelected(int position, ImageView thumbnail);
}

}

，错误日志为

java.lang.NullPointerException: Attempt to invoke interface method 'void com.example.recyclerviewah.AlbumsAdapter$AlbumsAdapterListener.onCardSelected(int, android.widget.ImageView)' on a null object reference
    at com.example.recyclerviewah.AlbumsAdapter$3.onClick(AlbumsAdapter.java:91)

我不明白我需要做什么