在RecyclerView中滚动时值会更改

Question

我创建了RecyclerViewAdapter，它通过int设置cardview背景，但是当我滚动一个大的列表时，颜色在不同的项目之间变化。

这是我的代码：

public class __MESSAGE_ListAdapter extends RecyclerView.Adapter<__MESSAGE_ListAdapter.ViewHolder>{
private Context context;
private List<__MESSAGE_Item> MessageItems;
AdapterViewCompat.OnItemClickListener mItemClickListener;


public class ViewHolder extends RecyclerView.ViewHolder{
    // each data item is just a string in this case
    public TextView title,writer,time,message,index, parent;
    public CardView cardView;
    public ViewHolder(View v) {
        super(v);
        title = (TextView) itemView.findViewById(R.id.messageTitle);
        time = (TextView) itemView.findViewById(R.id.messageTime);
        writer = (TextView) itemView.findViewById(R.id.messageWriter);
        message = (TextView) itemView.findViewById(R.id.messageContent);
        index = (TextView) itemView.findViewById(R.id.messageIndex);
        parent = (TextView) itemView.findViewById(R.id.messageParent);
        cardView = (CardView) itemView.findViewById(R.id.card_view);
    }
}

public void add(int position, __MESSAGE_Item item) {
    MessageItems.add(position, item);
    notifyItemInserted(position);
}

public void remove(__MESSAGE_Item name) {
    int position = MessageItems.indexOf(name);
    MessageItems.remove(position);
    notifyItemRemoved(position);
}

// Provide a suitable constructor (depends on the kind of dataset)
public __MESSAGE_ListAdapter(List<__MESSAGE_Item> myDataset, Context context) {
    MessageItems = myDataset;
}

// Create new views (invoked by the layout manager)
@Override
public __MESSAGE_ListAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                        int viewType) {
    // create a new view
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.message_list_item, parent, false);
    // set the view's size, margins, paddings and layout parameters
    ViewHolder vh = new ViewHolder(v);
    this.context = parent.getContext();
    return vh;
}

// Replace the contents of a view (invoked by the layout manager)
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    // - get element from your dataset at this position
    // - replace the contents of the view with that element
    final __MESSAGE_Item name = MessageItems.get(position);

    if (Integer.parseInt(MessageItems.get(position).getIndex()) != 0)
    {
        holder.title.setText(MessageItems.get(position).getIndex() + "." + MessageItems.get(position).getTitle());
        holder.parent.setText(MessageItems.get(position).getParent());
    }
    else {
        holder.title.setText(MessageItems.get(position).getTitle());
        holder.parent.setText("");
        holder.parent.setVisibility(View.GONE);
    }
    //Set writer
    holder.writer.setText(MessageItems.get(position).getWriter());

    //Timestamp to Date
    holder.time.setText(new SimpleDateFormat("hh:mm dd/MM/yyyy")
            .format(new Date(MessageItems.get(position).getTime() * 1000L)));

    //Check if the message is empty - not work!
    if(MessageItems.get(position).getMessage() != "")
    {
        UrlImageParser p = new UrlImageParser(holder.message, context);
        Spanned htmlSpan = Html.fromHtml(MessageItems.get(position).getMessage(), p, null);
        holder.message.setText(htmlSpan);
        //Make links
        Linkify.addLinks(holder.message, Linkify.WEB_URLS);

    }
    else {
        holder.message.setVisibility(View.GONE);
    }

    //Set index
    holder.index.setText(MessageItems.get(position).getIndex());

    //Set colour by level
    int messageLevel = MessageItems.get(position).getLevel();
    if (messageLevel >= 2)
    {
        if (messageLevel == 2)
        {
            holder.cardView.setCardBackgroundColor(context.getResources().getColor(R.color.level_1));
        }
        else if(messageLevel == 3)
        {
            holder.cardView.setCardBackgroundColor(context.getResources().getColor(R.color.level_2));
        }
        else if(messageLevel == 4)
        {
            holder.cardView.setCardBackgroundColor(context.getResources().getColor(R.color.level_3));
        }
        else if(messageLevel == 5)
        {
            holder.cardView.setCardBackgroundColor(context.getResources().getColor(R.color.level_4));
        }
        else
        {
            holder.cardView.setCardBackgroundColor(context.getResources().getColor(R.color.level_5));
        }
    }
}
// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
    return MessageItems.size();
}

}

知道怎么解决吗？ 我看到了关于listview适配器的这个问题，但问题不在这里。 有关convertView == null的问题，但这段代码在哪里？