接口 ProgressListener

// Adding an upload progress listener that completes when all known changes have been
// uploaded.
session.addUploadProgressListener(ProgressMode.CURRENT_CHANGES, new ProgressListener() {
  @Override
   public void onChange(Progress progress) {
     activity.runOnUiThread(new Runnable() {
       @Override
        public void run() {
          updateProgressBar(progress);
        }
     });
     if (progress.isTransferComplete() {
       session.removeProgressListener(this);
     }
   }
});