无法在android中处理线程处理程序

Question

我有这段代码：

public void onClick(View v) {

        switch (v.getId()) {

        case R.id.bRegister:
            dialog.show(Main.this, "Loading..", "", true, true);
            RequestThread requestThread = new RequestThread();
            requestThread.start();

            break;
        }
    }

    String Response = "";

    class RequestThread extends Thread {

        public void run() {

            String NAME = name.getText().toString();
            String PHONE = phone.getText().toString();
            String url = baseUrl + "creatdriver.php?name=" + NAME + "&phone="
                    + PHONE + "&latitude=23.234541" + "&longitude=90.123241";

            if (HTTPmanage.isConnected(getApplicationContext())) {
                Response = HTTPmanage.httpRetrieve(url);
            } else {

                Response = "Net Connection Unavailable";
            }
            handler.sendEmptyMessage(0);
        }

    }

    Handler handler = new Handler() {

        public void handleMessage(android.os.Message msg) {

            dialog.dismiss();
            Toast.makeText(getApplicationContext(), Response, Toast.LENGTH_LONG)
                    .show();

        }
};

通过这段代码，我将一些数据插入MySQL.Everything工作正常但是当进度对话框完成时强制关闭并且有NULL POINTER异常，但我无法弄清楚我在哪里犯了错误？