在asyncTask中的textview中的java.lang.NullPointerException

如果我使用以下代码，我将没有错误，但会有一个冻结时间 .

`@Override protected void onCreate（Bundle savedInstanceState）{// TODO自动生成的方法stub super.onCreate（savedInstanceState）; StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder（） . permitAll（） . build（）; StrictMode.setThreadPolicy（政策）;的setContentView（R.layout.profilepic）;

initialize();

    Bundle bundle = getIntent().getExtras();
    email = bundle.getString("Email");

    ArrayList<NameValuePair> postParameters;
    String response = null;

    postParameters = new ArrayList<NameValuePair>();
    postParameters.add(new BasicNameValuePair("emaillog", email));              

    try {
        response = CustomHttpClient.executeHttpPost("http://whatstherex.info/checkU.php", postParameters);

        res = response.toString();

        res = res.replaceAll("null", "");                   

        username = res.toString();

        tvProfilePic.setText("Hi " + username + ", you are encourage to add a profile picture.");

    }catch(Exception e){
        res = e.toString();
        tvProfilePic.setText(res);

    }
}`

但是，如果我使用asynctask和progressDialog这样的代码：

`@Override protected void onCreate（Bundle savedInstanceState）{// TODO自动生成的方法stub super.onCreate（savedInstanceState）; StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder（） . permitAll（） . build（）; StrictMode.setThreadPolicy（政策）;的setContentView（R.layout.profilepic）;

initialize();

    getUsername();

}

私有的AsyncTask任务;

public void getUsername(){      
    Bundle bundle = getIntent().getExtras();
    email = bundle.getString("Email");

    task = new AsyncTask<String, Void, String>() {

        ProgressDialog dialog;
        ArrayList<NameValuePair> postParameters;
        String response = null;

        @Override
        protected void onPreExecute() {
            //
            ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>();
            postParameters.add(new BasicNameValuePair("emaillog", email));

            dialog = new ProgressDialog(Profilepic.this, ProgressDialog.STYLE_SPINNER);
            dialog.setMessage("Loading Data...");       

            dialog.show();
        }

        @Override
        protected String doInBackground(String... params) {
            //
            try {
                response = CustomHttpClient.executeHttpPost("http://whatstherex.info/checkU.php", postParameters);

                res = response.toString();

                res = res.replaceAll("null", "");   

                username = res.toString();

                return username;
            }catch(Exception e){
                res = e.toString();
                return res;
            }
        }

        @Override
        protected void onPostExecute(String result) {               
            if(result.length()< 25){
                username = result;
                tvProfilePic.setText("Hi " + result + ", you are encourage to add a profile picture.");
                dialog.dismiss();
            }else{
                tvProfilePic.setText(result);
                dialog.dismiss();
            }
        }
    };
    task.execute(); 
}`

然后我将在textview中获取java.lang.NullPointerException .

什么问题可以任何人指导我？谢谢