我找到了解决方案-如果有人对此感兴趣，那就是工作代码:

I found the solution - if anyone is interested here is the working code:

private DropboxAPI<AndroidAuthSession> mDBApi;//global variable

File tmpFile = new File(fullPath, "IMG_2012-03-12_10-22-09_thumb.jpg");

FileInputStream fis = new FileInputStream(tmpFile);

            try {
                DropboxAPI.Entry newEntry = mDBApi.putFileOverwrite("IMG_2012-03-12_10-22-09_thumb.jpg", fis, tmpFile.length(), null);
            } catch (DropboxUnlinkedException e) {
                Log.e("DbExampleLog", "User has unlinked.");
            } catch (DropboxException e) {
                Log.e("DbExampleLog", "Something went wrong while uploading.");
            }