如何从BackgroundWorker重定向到另一个活动？

I have created a php page and a login page for verification but after login success it just pops up a login success message. I want my app to redirect to another activity after successfull login.how do i do it via backgroundworker

package com.project.v_app;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;

import android.app.AlertDialog;
import android.content.Context;
import android.os.AsyncTask;

public class BackgroundWorker extends AsyncTask<String, Void, String> {
    Context context;
    AlertDialog alertDialog;
    BackgroundWorker (Context ctx){
        context = ctx;
    }
    @Override
    protected String doInBackground(String... params) {
        String type = params[0];
        String login_url = "http://192.168.0.103/login.php";
        if(type.equals("login"))
        {
            try {
                String user_name = params[1];
                String password = params[2];
                URL url = new URL(login_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);
                OutputStream outputStream = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
                String post_data = URLEncoder.encode("user_name","UTF-8")+"="+URLEncoder.encode(user_name,"UTF-8")+"&"
                        +URLEncoder.encode("password","UTF-8")+"="+URLEncoder.encode(password,"UTF-8");
                bufferedWriter.write(post_data);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();
                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1"));
                String result="";
                String line="";
                while((line = bufferedReader.readLine())!=null)
                {
                    result +=line;
                }
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();
                return result;
            } catch (MalformedURLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return null;
    }

    @Override
    protected void onPreExecute() {
    alertDialog = new AlertDialog.Builder(context).create();
    alertDialog.setTitle("Login Status");
    }

    @Override
    protected void onPostExecute(String result) {
        alertDialog.setMessage(result);
        alertDialog.show();
    }

    @Override
    protected void onProgressUpdate(Void... values) {
        // TODO Auto-generated method stub
        super.onProgressUpdate(values);
    }

}

In the onPostExecute() method you should start another activity like this:

                    Intent intent = new Intent(getActivity().getApplicationContext(), OtherActivity.class);
                    startActivity(intent);

In onPreExecute,onPostExecute you can access UI elements.

So you may do like this

    @Override
            protected void onPreExecute() {
    //will execute first      
      alertDialog = new AlertDialog.Builder(context).create();
            alertDialog.setTitle("Login Status");
            alertDialog.setMessage("Message");
                alertDialog.show();
        } 

        @Override
            protected void onPostExecute(String result) {
//You may check some condition             
Intent anothercallActivity=new Intent(context,ActivityClassName.class);
            startActivity(anothercallActivity);
alertDialog.dismiss();     
            }

Try to specify the next flags to your intent

Intent i = new Intent(getBaseContext(), YourActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
getApplication().startActivity(i);