code: public static void getVideoThumbnail(String videoPath, final VideoThumbnailCallback cb){
          new AsyncTask<String, Void, Bitmap>(){
              @Override
              protected Bitmap doInBackground(String... params) {
                  if(params.length > 0) {
                      String path = params[0];
                      if(!TextUtils.isEmpty(path)){
                          return getVideoThumbnail(path);
                      }
                  }
                  return null;
              }
  
              @Override
              protected void onPostExecute(Bitmap bitmap) {
                  cb.onThumbnail(bitmap);
              }
          }.execute(videoPath);
      }
docs: Get the thumbnail of a video asynchronously
  
  @param videoPath     the path to the video
  @param cb            the callback