How to use progress dialog in AsyncTask in android

Question

I am developing an app which requires a user to login.The login is working ok through a url. However when i add an AsyncTask to add a progress dialog,the app does not change intent.I have tried every possible method i know in vain. below is the code:

  package com.epolicing;

import java.util.ArrayList;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;

import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class LoginActivity extends Activity implements OnClickListener{
    Button loginButton;
    EditText usernme,passwrd;
    TextView error;
    String username,password;
    static final int Dialog_logging_in=1;
    boolean userverified=false;

    // Session Manager Class
     SessionManager session;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login); 
        session = new SessionManager(getApplicationContext()); 
        loginButton = (Button) findViewById(R.id.loginButton);
        usernme = (EditText) findViewById(R.id.UserName);
        passwrd=(EditText) findViewById(R.id.password);
        username=usernme.getText().toString().trim();
        password=passwrd.getText().toString().trim();
        error=(TextView)findViewById(R.id.errorTextView);
        loginButton.setOnClickListener(this);
    }

     protected Dialog onCreateDialog(int id){
      Dialog dialog = null;
      switch(id){
      case Dialog_logging_in:
          ProgressDialog.show(LoginActivity.this,"","Authenticating user...");
          break;
          default:
              dialog=null;
      }
      return dialog;

     }


    public void onClick(View v) {
        switch(v.getId()){
        case R.id.loginButton:
            String user,pass;
            user=usernme.getText().toString();
            pass=passwrd.getText().toString();

            if(user.equals("")||pass.equals("")){       
                message();
            }
            else {
                new log_in().execute(this);
            }
            break;
            }

        }

    //login method
      public void login() {
                ArrayList<NameValuePair>postParameters=new ArrayList<NameValuePair>();
                postParameters.add(new BasicNameValuePair("username",usernme.getText().toString()));
                postParameters.add(new BasicNameValuePair("password",passwrd.getText().toString().trim()));

                //String valid="1";
                String response=null;
                try{
                    response=CustomHttpClient.executeHttpPost("http://10.0.2.2/epolicing/tologin.php",postParameters);
                    String res=response.toString();
                    res=res.replaceAll("\\s+","");
                    if(res.equals("0")) {
                 error.setText("Wrong password or username combination");
                    }
                    else {
                        String usern=usernme.getText().toString().trim();
                        session.createLoginSession(usern,res);
                        userverified=true;
                        //Intent intent=new Intent(LoginActivity.this,menu.class);
                        //startActivity(intent);    
                    }
                }
                catch(Exception e){
                    error.setText(e.toString());

                }

      }


      public void message(){
        Context context=getApplicationContext();
        CharSequence text="username and/or password cannot be blank";
        int duration=Toast.LENGTH_LONG;
        Toast toast=Toast.makeText(context, text, duration);
        toast.show();
    }

     private class log_in extends AsyncTask<LoginActivity,Void,LoginActivity>{
        @Override
         protected void onPreExecute(){
            showDialog(Dialog_logging_in); 
         }
        @Override
        protected LoginActivity doInBackground(LoginActivity... Params) {
            login();
            return null;
        }
        protected void onPostExecute(LoginActivity params){
            super.onPostExecute(params);
            //dismissDialog(Dialog_logging_in);
            if(userverified==true){
                Intent intent=new Intent(LoginActivity.this,menu.class);
                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                LoginActivity.this.startActivity(intent);
            }

        }


     }
}

Here is the log:

01-20 19:36:53.685: E/WindowManager(1191): Activity com.epolicing.LoginActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@40555c68 that was originally added here
01-20 19:36:53.685: E/WindowManager(1191): android.view.WindowLeaked: Activity com.epolicing.LoginActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@40555c68 that was originally added here
01-20 19:36:53.685: E/WindowManager(1191):  at android.view.ViewRoot.<init>(ViewRoot.java:258)
01-20 19:36:53.685: E/WindowManager(1191):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
01-20 19:36:53.685: E/WindowManager(1191):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
01-20 19:36:53.685: E/WindowManager(1191):  at android.view.Window$LocalWindowManager.addView(Window.java:424)
01-20 19:36:53.685: E/WindowManager(1191):  at android.app.Dialog.show(Dialog.java:241)
01-20 19:36:53.685: E/WindowManager(1191):  at android.app.ProgressDialog.show(ProgressDialog.java:107)
01-20 19:36:53.685: E/WindowManager(1191):  at android.app.ProgressDialog.show(ProgressDialog.java:90)
01-20 19:36:53.685: E/WindowManager(1191):  at android.app.ProgressDialog.show(ProgressDialog.java:85)
01-20 19:36:53.685: E/WindowManager(1191):  at com.epolicing.LoginActivity.onCreateDialog(LoginActivity.java:50)
01-20 19:36:53.685: E/WindowManager(1191):  at android.app.Activity.onCreateDialog(Activity.java:2482)
01-20 19:36:53.685: E/WindowManager(1191):  at android.app.Activity.createDialog(Activity.java:882)
01-20 19:36:53.685: E/WindowManager(1191):  at android.app.Activity.showDialog(Activity.java:2557)
01-20 19:36:53.685: E/WindowManager(1191):  at android.app.Activity.showDialog(Activity.java:2524)
01-20 19:36:53.685: E/WindowManager(1191):  at com.epolicing.LoginActivity$log_in.onPreExecute(LoginActivity.java:120)
01-20 19:36:53.685: E/WindowManager(1191):  at android.os.AsyncTask.execute(AsyncTask.java:391)
01-20 19:36:53.685: E/WindowManager(1191):  at com.epolicing.LoginActivity.onClick(LoginActivity.java:71)
01-20 19:36:53.685: E/WindowManager(1191):  at android.view.View.performClick(View.java:2485)
01-20 19:36:53.685: E/WindowManager(1191):  at android.view.View$PerformClick.run(View.java:9080)
01-20 19:36:53.685: E/WindowManager(1191):  at android.os.Handler.handleCallback(Handler.java:587)
01-20 19:36:53.685: E/WindowManager(1191):  at android.os.Handler.dispatchMessage(Handler.java:92)
01-20 19:36:53.685: E/WindowManager(1191):  at android.os.Looper.loop(Looper.java:123)
01-20 19:36:53.685: E/WindowManager(1191):  at android.app.ActivityThread.main(ActivityThread.java:3683)
01-20 19:36:53.685: E/WindowManager(1191):  at java.lang.reflect.Method.invokeNative(Native Method)
01-20 19:36:53.685: E/WindowManager(1191):  at java.lang.reflect.Method.invoke(Method.java:507)
01-20 19:36:53.685: E/WindowManager(1191):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
01-20 19:36:53.685: E/WindowManager(1191):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
01-20 19:36:53.685: E/WindowManager(1191):  at dalvik.system.NativeStart.main(Native Method)

Help will be highly appreciated.Thanks.

Solution

no need to return current Activity instance from doInBackground because AsyncTask is inner class of Activity so you just use LoginActivity.this to start next Activity change your AsyncTask class as :

   private class log_in extends AsyncTask<String,Void,String>{
        ProgressDialog pDialog;
        @Override
         protected void onPreExecute(){
            pDialog = new ProgressDialog(LoginActivity.this);
            pDialog.setMessage("Authenticating user...");
            pDialog.show();
         }
        @Override
        protected String doInBackground(String... params) {
            login();
            return null;
        }
        protected void onPostExecute(String params){
            super.onPostExecute(params);
            pDialog.dismiss();
            if(userverified==true){
                Intent intent=new Intent(LoginActivity.this,menu.class);
                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                LoginActivity.this.startActivity(intent);
            }
           else{
               error.setText("Wrong password or username combination");
            }

        }

     }

because it's not possible to updating UI elements from doInBackground and you are trying to set textview text inside login() method instead of changing Textview text just make userverified==false