问从dropbox下载文件时未调用onProgressUpdate()

EN

package com.example.downloadupload;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Environment;
import android.util.Log;
import com.dropbox.client2.DropboxAPI;
import com.dropbox.client2.ProgressListener;
import com.dropbox.client2.android.AndroidAuthSession;
import com.dropbox.client2.exception.DropboxException;

public class DownloadFile extends AsyncTask<Void, Long, Boolean> {

    DropboxAPI<AndroidAuthSession> dDBApi;
    Context dContext;
    private final  ProgressDialog uDialog;
    private long dFileLen;
    long bytess;

    public DownloadFile(Context context,
        DropboxAPI<AndroidAuthSession> mDBApi) {
        dDBApi=mDBApi;
        dContext=context.getApplicationContext();
        uDialog = new ProgressDialog(context);
        uDialog.setMax(100);
        uDialog.setMessage("Downloading Image");
        uDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        uDialog.show();
    }

@Override
protected Boolean doInBackground(Void... params) {

    String path1= Environment.getExternalStorageDirectory()+"/log.txt";
    BufferedOutputStream out=null;
    try {
        File file = new File(path1);
        out = new BufferedOutputStream(new FileOutputStream(file));
        dDBApi.getFile("/log.txt", null,out,new ProgressListener() {

          /* @Override
           public long progressInterval() {
               // Update the progress bar every half-second or so
               return 500;
           }*/

            @Override
            public void onProgress(long bytes, long total) {
                // TODO Auto-generated method stub
                bytess=bytes;
                publishProgress(bytes);
            }
        });
    } catch (DropboxException e) {
        Log.e("DbExampleLog", "Something went wrong while downloading.");
    } catch (FileNotFoundException e) {
        Log.e("DbExampleLog", "File not found.");
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } finally {
        if (out != null) {
            try {
                out.close();
            } catch (IOException e) {}
        }
    }
    return null;
}

@Override
protected void onProgressUpdate(Long... progress) {
    // TODO Auto-generated method stub
    super.onProgressUpdate(progress);
    int percent = (int)(100.0*(double)progress[0]/bytess + 0.5);
    uDialog.setProgress(percent);
    System.out.println("Hi progressing");
}

@Override
protected void onPostExecute(Boolean result) {
    // TODO Auto-generated method stub
    super.onPostExecute(result);

    uDialog.dismiss();
    System.out.println("calling post execute");
}


}