从视频网址获取缩略图并在gridview上加载非常慢

Question

我正在从 sdcard 获取视频 url 列表并传递给适配器。在适配器中，从视频的 url 创建缩略图位图。加载 gridview 变得非常慢，滚动也非常慢。有什么方法可以更快更轻松地从 sd 卡中获取缩略图。

@Override
    public View getView(int position, View convertView, ViewGroup parent) {

        final ViewHolder holder;
        if (convertView == null) {

            convertView = infalter.inflate(R.layout.gallery_item, null);
            holder = new ViewHolder();
            holder.imgQueue = (ImageView) convertView.findViewById(R.id.imgQueue);

            holder.imgQueueMultiSelected = (ImageView) convertView
                    .findViewById(R.id.imgQueueMultiSelected);

            convertView.setTag(holder);

        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.imgQueue.setTag(position);

        try {

            Bitmap bitmap=ThumbnailUtils.createVideoThumbnail(data.get(position).sdcardPaththumbvideo, MediaStore.Video.Thumbnails.MINI_KIND);

            if (bitmap==null) {
                holder.imgQueue.setImageResource(R.drawable.no_media);
            }
            else{
                holder.imgQueue.setImageBitmap(bitmap);
            }



        } catch (Exception e) {
            e.printStackTrace();
        }

        return convertView;
    }

Answer 1

将ThumbnailUtils.createVideoThumbnail() 移出主应用程序线程。在this sample project 中，我使用the SmartImageView library 异步加载缩略图，将我的自定义VideoThumbnailImage 作为ViewBinder 应用到我的SimpleCursorAdapter 上，显示查找所有视频的结果：

  private static class ThumbnailBinder implements
      SimpleCursorAdapter.ViewBinder {
    @Override
    public boolean setViewValue(View v, Cursor c, int column) {
      if (column == c.getColumnIndex(MediaStore.Video.Media._ID)) {
        VideoThumbnailImage thumb=
            new VideoThumbnailImage(
                                    c.getInt(column),
                                    MediaStore.Video.Thumbnails.MICRO_KIND);

        ((SmartImageView)v).setImage(thumb,
                                     R.drawable.ic_media_video_poster);

        return(true);
      }

      return(false);
    }
  }

  private static class VideoThumbnailImage implements SmartImage {
    private int videoId;
    private int thumbnailKind;

    VideoThumbnailImage(int videoId, int thumbnailKind) {
      this.videoId=videoId;
      this.thumbnailKind=thumbnailKind;
    }

    @Override
    public Bitmap getBitmap(Context ctxt) {
      return(MediaStore.Video.Thumbnails.getThumbnail(ctxt.getContentResolver(),
                                                      videoId,
                                                      thumbnailKind,
                                                      null));
    }
  }