RecyclerView 滚动到顶部本身

Question

Hi I have a RecyclerView which I use to display images in two columns. ArrayList of movies holds 60 String of URL's for images.So the images are loaded fine into the ImageViews. When I scroll down everything works fine and smooth, then I reach bottom and scroll up, for a while it scrolls ok, but then it scrolls to the very top and I actually see all the photos between trying to load. I looked for this issue, but haven't found a cause of this scrolling issue. But if I have just 20 items in the list everything works great

Here's the Adapter's code:

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {
private ArrayList<Movie> movies;
private Context context;
private int newWidth;
private int newHeight;

public CustomAdapter(ArrayList<Movie> movies, Context context) {
    this.movies = movies;
    this.context = context;
    int screenWidth = context.getResources().getDisplayMetrics().widthPixels;
    int orientation = context.getResources().getConfiguration().orientation;
    newWidth = screenWidth / (orientation == Configuration.ORIENTATION_LANDSCAPE ? 3 : 2);
    newHeight = (int) (((double) newWidth / 185) * 278);

}

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

@Override
public void onBindViewHolder(ViewHolder holder, int position) {

    Picasso.with(context)
            .load(movies.get(position).url)
            .resize(newWidth, newHeight)
            .into(holder.imageView);
}

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

public static class ViewHolder extends RecyclerView.ViewHolder {
    final ImageView imageView;

    public ViewHolder(View itemView) {
        super(itemView);
        imageView = (ImageView) itemView.findViewById(R.id.pic);
    }
}
}

Thank you

Answer 1

For me, I've noticed that if you use "match_parent" for some Views (ViewPager with RecyclerViews in my case) instead of constraints for ConstraintsLayout, this issue can occur.

I've reported it here .

For now, my workaround/fix was to set constraints.

Answer 2

I've found the solution.The problem was that my ImageView didn't have a fixed size, it got it when picture is being downloaded, that's why when I scrolled to top - there happened to be all of the previous ImageViews in one screen with 0 height and without picture, but when the picture is being dowloaded the ImageView size extended and looks like the RecyclerView scrolls to the first of the visible ImageView.

So I added this code to my CustomAdapter

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_movie, parent, false);
    ImageView viewById = (ImageView) view.findViewById(R.id.poster);
    viewById.setMinimumWidth(newWidth);
    viewById.setMinimumHeight(newHeight);
    return new ViewHolder(view);
} 

this is how I change my ImageView size to the one I want before the picture actually being downloaded.

Also added a ProgressBar to look better.

@Override
public void onBindViewHolder(final ViewHolder holder, int position) {
    holder.progressBar.setVisibility(View.VISIBLE);

    Picasso.with(context)
            .load(movies.get(position).postersUrl)
            .resize(0, newHeight)
            .noFade()
            .into(holder.imageView, new Callback() {
                @Override
                public void onSuccess() {
                    holder.progressBar.setVisibility(View.INVISIBLE);
                }

                @Override
                public void onError() {

                }
            });