Android Image disappear in RecyclerView after Scrolling list up and down?

问题

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);
    }
}}

回答1:

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).

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);
}

where cache would be your own implementation.

回答2:

do like this

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

来源：https://stackoverflow.com/questions/36819235/android-image-disappear-in-recyclerview-after-scrolling-list-up-and-down

标签

android

android-volley

listadapter