Загрузить файл с Android на сервер, используя OkHttp и PHP

Я создаю PHP-скрипт для Android-загрузчика. Но я не могу загрузить файл csv из локальной папки Android.

PHP sclipt может работать один.

Ошибка Undefined index: upfile в /example/html/php/uploadfile.php online 9

не выбирать файл

public class MainActivity extends Activity {

TextView outputText;
Button sendData;
EditText edtUser, edtPass;
final String URL = "http://example/php/uploadfile.php";


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    outputText = (TextView) findViewById(R.id.textView1);
    outputText.setMovementMethod(new ScrollingMovementMethod());
    sendData = (Button) findViewById(R.id.button1);
    edtUser = (EditText) findViewById(R.id.editText1);
    edtPass = (EditText) findViewById(R.id.editText2);

    String Text = "Tue Oct 06 18:56:24 JST 2015,Tue Oct 06 18:57:12 JST 2015,35.4708118,139.6251623\n";

    try {
        OutputStream out = openFileOutput("GPS_log2.csv", MODE_APPEND);
        PrintWriter writer =
                new PrintWriter(new OutputStreamWriter(out, "UTF-8"));
        writer.append(Text);
        writer.close();
    } catch (IOException e) {
        e.printStackTrace();
    }

    sendData.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            OkHttpHandler handler = new OkHttpHandler();

            String result = null;

            try {
                result = handler.execute(URL).get();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
            outputText.append(result + "\n");
        }
    });
  }
}


public class OkHttpHandler extends AsyncTask<String, Void, String> {

public static final MediaType MEDIA_TYPE_CSV
        = MediaType.parse("text/csv; charset=utf-8");

OkHttpClient client = new OkHttpClient();

public OkHttpHandler(){

}

@Override
protected String doInBackground(String........params){

    String filename = "GPS_log2.csv";
    Log.d("doInBackground", "start");

    Request request = new Request.Builder()
            .url("http://160.16.84.183/php/uploadfile.php")
            .post(RequestBody.create(MEDIA_TYPE_CSV,filename))
            .build();

    try{
        Response response = client.newCall(request).execute();
        if(!response.isSuccessful())
            throw new IOException("Unexpected code " + response.toString());
        return response.body().string();

    }catch(Exception e){
        e.printStackTrace();
        Log.d("Response ",e.getMessage());

    }
    return null;

}

if (is_uploaded_file($_FILES["upfile"]["tmp_name"])) {
if (move_uploaded_file($_FILES["upfile"]["tmp_name"], "/var/www/html/php/" . $_FILES["upfile"]["name"])) {
chmod("/var/www/html/php/" . $_FILES["upfile"]["name"], 0644);
echo $_FILES["upfile"]["name"] . "file uploaded";
} else {
echo "cannot file upload";
}
} else {
echo "do not choice file";
}