上下滚动列表后，Android Image在RecyclerView中消失了吗? [英] Android Image disappear in RecyclerView after Scrolling list up and down?

问题描述

我有一个RecyclerView来显示列表数据，但是在上下滚动之后，使用Volley从URL加载的图像消失并再次出现.我知道在阅读此 ListView的回收机制如何工作之后，该列表将回收物品.这是我的适配器，我在哪里弄错了?

I have a RecyclerView to display list data but after Scrolling up and down, a image load from url using Volley disappear and appear again. I know that the list will recycle item after read this How ListView's recycling mechanism works. Here is my Adapter, where did I wrong?

public class PostAdapter extends RecyclerView.Adapter<PostAdapter.ViewHolder> {

private ArrayList<Post> posts;
private Context context;
private ImageLoader imageLoader;

public PostAdapter(ArrayList<Post> posts, Context context) {
    this.posts = posts;
    this.context = context;
    imageLoader = MySingleton.getInstance(context).getImageLoader();
}

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

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    holder.name.setText(posts.get(position).getName());
    holder.timestamp.setText(posts.get(position).getTimestamp());
    holder.status.setText(posts.get(position).getStatus());
    holder.avatar.setImageUrl(Constants.URL_IMAGE + posts.get(position).getAvatar(), imageLoader);
    if(!posts.get(position).getImage().equals("")) {
        holder.image.setVisibility(View.VISIBLE);
        holder.image.setImageUrl(Constants.URL_IMAGE + posts.get(position).getImage(), imageLoader);
    } else {
        holder.image.setVisibility(View.GONE);
    }
}

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

public static class ViewHolder extends RecyclerView.ViewHolder {
    NetworkImageView image, avatar;
    TextView status, timestamp, name;

    public ViewHolder(View itemView) {
        super(itemView);
        avatar = (NetworkImageView) itemView.findViewById(R.id.profilePic);
        image = (NetworkImageView) itemView.findViewById(R.id.feedImage1);
        status = (TextView) itemView.findViewById(R.id.txtStatusMsg);
        name = (TextView) itemView.findViewById(R.id.name);
        timestamp = (TextView) itemView.findViewById(R.id.timestamp);
    }
}}

推荐答案

在您的实现中，每次绑定到视图持有者时，您都会调用setImageUrl().尽管ImageLoader支持并使用缓存，但它是在网络级别上的，因此在设置URL和显示图像(消失并显示)之间存在短暂的延迟.

In your implementation you're calling setImageUrl() every time you bind to the view holder. Eventhough ImageLoader supports and uses a cache, it's on the networking level, giving you a short delay between setting the url and displaying the image (disappear and appear).

为了更好地处理此问题，您应该为图像实现内存中的缓存，并直接将其设置为

To handle this better, you should implement an in-memory cache for your images and set these directly like

String image = posts.get(position).getImage();
if("".equals(image)) {
    holder.image.setVisibility(View.GONE);
} else if (cache.hasImage(image)) {
    holder.image.setVisibility(View.VISIBLE);
    holder.image.setImageBitmap(cache.getImage(image));
} else {
    holder.image.setVisibility(View.VISIBLE);
    holder.image.setImageUrl(Constants.URL_IMAGE + image, imageLoader);
}

其中cache是您自己的实现.

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