无法将文件上传到Dropbox ANDROID

Question

我无法将文件上传到Dropbox。我没有收到任何错误，app文件夹是在我的帐户中创建的，但该文件未上传到dropbox。这是我的代码：

public void exportDataInCSV(final String file_name,
            final ArrayList<Assessment> assessments, final boolean dropBox)
            throws IOException {

        final File folder = new File(Environment.getExternalStorageDirectory()
                + "/MYDIR");

        boolean var = false;
        if (!folder.exists())
            var = folder.mkdir();

        System.out.println("" + var);

        final String filename = folder.toString() + "/" + file_name + ".csv";

        // show waiting screen
        CharSequence contentTitle = getString(R.string.app_name);

        final ProgressDialog progDailog = ProgressDialog.show(DataExport.this,
                contentTitle, "Exporting data...", true);// please
                                                            // wait

        new Thread() {
            public void run() {
                try {

                    FileWriter fw = new FileWriter(filename);

                    fw.append("MYNAME");
                    fw.append(',');

                    fw.append("MYSIRNAME");

                    fw.close();
                    if (dropBox) {

                        File file = new File(folder.toString() + "/"
                                + file_name + ".csv");
                        FileInputStream inputStream = new FileInputStream(file);
                        Entry response = mDBApi.putFile("/magnum-opus.txt",
                                inputStream, file.length(), null, null);

                    }
                } catch (Exception e) {
                }
                progDailog.dismiss();
            }
        }.start();

    }

有人可以帮助我并告诉我如何使用文件写入器将我正在创建的文件上传到Dropbox，该文件也会保存到手机的SD卡中。