从Dropbox下载到Android Sdcard时获取空图像

Question

1. 我想从Dropbox下载特定图片，然后保存到SD卡。

2. 按钮后单击文件夹在Sdcard中创建，图像也保存在该文件夹中。

问题：  图像尺寸显示为 0 Kb

点击图片显示黑屏。

请帮我解决这个问题

按钮点击下载图片

Download.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {  
        File file1 = new File("/Photos/Picture_2015-07-06_13-41-04.png");//A specific Picture from Dropbox.
        downloadDropboxFile(file1);
}});

private boolean downloadDropboxFile(File fileSelected) {
    String path = Environment.getExternalStorageDirectory().getAbsolutePath() + "/MYfolder";

    File dir = new File(path);
    if (!dir.exists())
        dir.mkdirs();
    try {
        File localFile = new File(dir + "/" + fileSelected.getName());
        if (!localFile.exists())
        {
            localFile.createNewFile();
            copy(fileSelected, localFile);
        } else {
            //showFileExitsDialog(fileSelected, localFile);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

    return true;
}

private void copy(final File fileSelected, final File localFile) {
    final ProgressDialog pd = ProgressDialog.show(DBRoulette.this,
                    "Downloading...", "Please wait...");
    new Thread(new Runnable() {
        @Override
        public void run() {
            BufferedInputStream br = null;
            BufferedOutputStream bw = null;
            DropboxInputStream fd;
            try {
                fd = mApi.getFileStream(fileSelected.getPath(),localFile.getPath());
                br = new BufferedInputStream(fd);
                bw = new BufferedOutputStream(new FileOutputStream(localFile));

                byte[] buffer = new byte[4096];
                int read;
                while (true) {
                    read = br.read(buffer);
                    if (read <= 0) {
                        break;
                    }
                    bw.write(buffer, 0, read);
                }
                pd.dismiss();
                Message message = new Message();
                message.obj = localFile.getAbsolutePath();
                message.what = 1;
                //mHandler.sendMessage(message);
            } catch (DropboxException e) {
                e.printStackTrace();
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (bw != null) {
                    try {
                        bw.close();
                        if (br != null) {
                            br.close();
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }).start();
}