如何在延迟加载的列表视图中有效地从SD卡生成和填充视频缩略图和图像缩略图

Question

我在同一个文件夹中有大约150个图像和150个视频，我需要用缩略图填充列表视图中的所有文件。一切正常，但速度太慢，因为它多次创建VideoThumbnail。我尝试了很多东西但是我无法使listview顺利进行。请看看我的代码。提前谢谢。

public class FilesAdapter extends ArrayAdapter<String> {
    private List<String> mpath;
    private Context mContext;

public FilesAdapter(Context context, List<String> path) {
    super(context, R.layout.fileadapter_list);
    this.mContext = context;
    this.mpath = path;
}

class Helper {
    public TextView txtTitle;
    public ImageView imageView;
}

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    if (convertView == null) {
        LayoutInflater mInflater = (LayoutInflater) mContext
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = mInflater.inflate(R.layout.fileadapter_list, null);
        Helper h = new Helper();
        h.txtTitle = (TextView) convertView.findViewById(R.id.txt);
        h.imageView = (ImageView) convertView.findViewById(R.id.img);
        convertView.setTag(h);
    }

    Helper myHelper = (Helper) convertView.getTag();

    File file = new File(mpath.get(position));

    myHelper.txtTitle.setText(file.getName());

    if (file.isDirectory()) {
        Picasso.with(mContext).load(R.drawable.folder)
                .placeholder(R.drawable.folder).error(R.drawable.folder)
                .into(myHelper.imageView);
    } else {
        String sitem = mpath.get(position);
        String item_ext = null;
        try {
            item_ext = sitem.substring(sitem.lastIndexOf("."),
                    sitem.length());
        } catch (IndexOutOfBoundsException e) {
            item_ext = "";
        }
        if (item_ext.equalsIgnoreCase(".jpeg")
                || item_ext.equalsIgnoreCase(".jpg")
                || item_ext.equalsIgnoreCase(".png")
                || item_ext.equalsIgnoreCase(".gif")
                || item_ext.equalsIgnoreCase(".tiff")) {
            myHelper.imageView.clearColorFilter();
            Picasso.with(mContext).load(Uri.fromFile(file))
                    .placeholder(R.drawable.holder).error(R.drawable.error)
                    .centerInside().resize(100, 100)
                    .into(myHelper.imageView);
        } else if (item_ext.equalsIgnoreCase(".m4v")
                || item_ext.equalsIgnoreCase(".3gp")
                || item_ext.equalsIgnoreCase(".wmv")
                || item_ext.equalsIgnoreCase(".mp4")
                || item_ext.equalsIgnoreCase(".ogg")
                || item_ext.equalsIgnoreCase(".wav")) {
            Bitmap bitmap = ThumbnailUtils.createVideoThumbnail(
                    file.getAbsolutePath(),
                    MediaStore.Video.Thumbnails.MICRO_KIND);

            Picasso.with(mContext).load(getImageUri(mContext, bitmap))
                    .centerInside().resize(100, 100)
                    .placeholder(R.drawable.holder).error(R.drawable.error)
                    .into(myHelper.imageView);
        }
    }
    return convertView;
}

public Uri getImageUri(Context inContext, Bitmap inImage) {
    ByteArrayOutputStream bytes = new ByteArrayOutputStream();
    inImage.compress(Bitmap.CompressFormat.JPEG, 20, bytes);
    String path = Images.Media.insertImage(inContext.getContentResolver(),
            inImage, "Title", null);
    return Uri.parse(path);
}

}