Android 获取视频缩略图

private Bitmap getThumbnai(String path){
        FFmpegMediaMetadataRetriever fmmr = new FFmpegMediaMetadataRetriever();
        Bitmap bitmap = null;
        try {
          fmmr.setDataSource(path);
          bitmap = fmmr.getFrameAtTime();
          if (bitmap != null) {
            Bitmap b2 = fmmr
                .getFrameAtTime(
                    4000000,
                    FFmpegMediaMetadataRetriever.OPTION_CLOSEST_SYNC);
            if (b2 != null) {
              bitmap = b2;
            }
            if (bitmap.getWidth() > 640) {// 如果图片宽度规格超过640px,则进行压缩
              bitmap = ThumbnailUtils.extractThumbnail(bitmap,
                  640, 480,
                  ThumbnailUtils.OPTIONS_RECYCLE_INPUT);
            }
          }
        } catch (IllegalArgumentException ex) {
          ex.printStackTrace();
        } finally {
          fmmr.release();
        }
        return bitmap;
    }

new AsyncTask<Void, Void, Bitmap>(){

            @Override
            protected Bitmap doInBackground(Void... arg0) {
                Bitmap b = MainActivity.this.getThumbnai(path);
                return b;
            }

            @Override
            protected void onPostExecute(Bitmap b) {
                if(b!=null){
                    Log.d("doubi", "b!=null");
                    image.setImageBitmap(b);
                    bar.setVisibility(View.GONE);
                    image.setVisibility(View.VISIBLE);
                    play.setVisibility(View.VISIBLE);
                }
            }
        }.execute();