AndroidでYouTubeのサムネイルをアス比を直して表示する｡ ref: http://qiita.com/Rompei/items/46ae14a49b7a383153db

CustomAdapter.java

public class CustomAdapter extends ArrayAdapter<VideoItems> {
    private LayoutInflater layoutInflater;
    private Context context;

    public CustomAdapter(Context context, int textViewResourceId, List<VideoItems> objects, RequestQueue queue) {
        super(context, textViewResourceId, objects);
        layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        this.context = context;
    }

    static class ViewHolder {
        ImageView image;
        TextView numView;
    }


    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        VideoItems videoItems = getItem(position);
        String thumbnailurl = videoItems.snippet.thumbnails.high.url;

        if (convertView == null) {
            convertView = layoutInflater.inflate(R.layout.list_search, parent, false);

            holder = new ViewHolder();
            holder.image = (ImageView) convertView.findViewById(R.id.iv_thumbnail);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        //Picassoはこの1行で実装できます｡
        Picasso.with(context).load(thumbnailurl).transform(new CropTransformer()).placeholder(R.drawable.thumback).error(android.R.drawable.ic_dialog_alert).into(holder.image);

        return convertView;
    }

    private class CropTransformer implements Transformation{
        @Override
        public Bitmap transform(Bitmap source){
            int width = source.getWidth();
            int height = source.getHeight();
            //width, height = (480, 360)

            int x = 0;

            //y座標の始点をセットする｡
            int y = (height-width*9/16)/2;

            //幅をそのままに､高さを計算する｡
            height = width*9/16;

            Bitmap result = Bitmap.createBitmap(source, x, y, width, height);
            if(result!=source){
                source.recycle();
            }
            return result;
        }

        @Override
        public String key(){
            return "Custom()";
        }

    }