Question

i got a small problem with interrupts. in my android login activity, i start a thread (which defines the duration of my session). what i want is that when im in a different activity/class and i press the logout button, i should stop the thread thats doing the countdown and be able to logIn again.

the only way i know to interrupt thereads are by

Thread.currentThread().interrupt();

but i dont want to interrupt the current thread, i want to interrupt the thread by its id, which im able to get by getId().

this is my activity class code:

import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.AndroidApp.R;
import com.AndroidApp.domain.Utente;
import com.AndroidApp.pagine.MenuPagina;


public class LoginActivity extends Activity {

    final String TAG = "LogIN";
    ArrayList<HashMap<String, String>> mylist;

    private Button bLogin, bExit;
    private EditText utente, passwd;
    private MediaPlayer mpButtonClick = null;
    private SharedPreferences mPreferences; 
    public Thread sessionTimer;
    public long tId = -1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);

        mPreferences = getSharedPreferences("CurrentUser", MODE_PRIVATE);

        SharedPreferences.Editor editor = mPreferences.edit();
        editor.clear();
        editor.commit();

        String nome = mPreferences.getString("nome", "Nessuno");
        setTitle("Sessione di : " + nome);
        Log.w("TotThreads", Integer.toString(Thread.activeCount()));
        if (MenuPagina.reset){
            Log.w("LogIn", "trying to interrupt");


            //this is where im trying to interrypt the thread



            MenuPagina.reset = false;
        }

        if (!checkLoginInfo()) {

            mpButtonClick = MediaPlayer.create(this, R.raw.button);

            bLogin = (Button)findViewById(R.id.bLogin);
            bLogin.setOnClickListener(new View.OnClickListener() {

                public void onClick(View view) {

                    mpButtonClick.start();

                    Log.v(TAG, "Trying to Login");
                    utente = (EditText)findViewById(R.id.etUtente);
                    passwd = (EditText)findViewById(R.id.etPassword);

                    String username = utente.getText().toString();
                    username = ("[e-mail]");
                    String password = md5(passwd.getText().toString());
                    Log.v(TAG, password);

                    XMLFunctionsLogin.getInstance().setNewURL("u=" + username + "&p=" + password);
                    String xml = XMLFunctionsLogin.getXML();
                    Document doc = XMLFunctionsLogin.xmlFromString(xml); 
                    int status = XMLFunctionsLogin.errStatus(doc); 

                    Log.v("status", Integer.toString(status));
                    if ((status == 0)) {
                        NodeList nodes = doc.getElementsByTagName("login"); 
                        Element e = (Element) nodes.item(0);
                        Utente utente = new Utente();
                        utente.setIdUtente(XMLFunctionsLogin.getValue(e, "idUtente"));
                        utente.setNome(XMLFunctionsLogin.getValue(e, "nome"));
                        utente.setCognome(XMLFunctionsLogin.getValue(e, "cognome"));
                        Log.v("utente", utente.getCognome().toString());

                        Log.v(TAG, "5");

                        List<NameValuePair> nvps = new ArrayList<NameValuePair>(2);
                        nvps.add(new BasicNameValuePair("utente", username));
                        nvps.add(new BasicNameValuePair("password", password));
                        Log.v(TAG, nvps.get(0).toString());
                        Log.v(TAG, nvps.get(1).toString());

                        // Store the username and password in SharedPreferences after the successful login
                        SharedPreferences.Editor editor = mPreferences.edit();
                        editor.putString("userName", username);
                        editor.putString("password", password);
                        editor.putString("idUtente", utente.getIdUtente());
                        editor.putString("nome", utente.getNome());
                        editor.putString("cognome", utente.getCognome());
                        editor.commit();


                        Log.v(TAG, "Successo");

                        sessionTimer = new Thread() {
                            @Override
                            public void run() {
                                long tId = Thread.currentThread().getId();
                                Log.w("TTthread Id", Long.toString(tId));
                                for (int i = 30; i >= 0; i -= 1) {
                                    if (i == 0) {
                                        System.out.print("timer finito");
                                        Log.i("Timer", "timer finito");
                                        LoginActivity.this.runOnUiThread(new Runnable() { 
                                            public void run() { 
                                                Toast.makeText(LoginActivity.this, "ti si è scaduta la sessione", Toast.LENGTH_LONG).show(); 
                                            }
                                        });
                                        Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
                                        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                                        startActivity(intent);
                                        //System.exit(0);
                                    } try {
                                        Thread.sleep(1000);
                                        Log.i("Timer", Integer.toString(i));
                                    } catch (InterruptedException e) {
                                        e.printStackTrace();
                                    } finally {
                                        finish();
                                    }
                                }
                            }

                        };
                        sessionTimer.start();


                        Log.v(TAG, "Successo2");


                        /*
                        Counter timer = new Counter();
                        timer.start();

                         */

                        Toast.makeText(LoginActivity.this, "LogIn con successo", Toast.LENGTH_SHORT).show();
                        Intent intent = new Intent(LoginActivity.this, MenuPagina.class);
                        startActivity(intent);

                    } else {
                        final String errorMessage = XMLFunctionsLogin.errStatusDesc(doc);
                        Log.v("fallimento", errorMessage);
                        LoginActivity.this.runOnUiThread(new Runnable() { 
                            public void run() { 
                                Toast.makeText(LoginActivity.this, errorMessage, Toast.LENGTH_LONG).show(); 
                            }
                        });

                        Intent intent = getIntent();
                        finish();
                        startActivity(intent);
                    }
                }

            });

            bExit = (Button)findViewById(R.id.bExit);
            bExit.setOnClickListener(new View.OnClickListener() {

                public void onClick(View view) {
                    mpButtonClick.start();
                    finish();
                }
            });
        }
    }

    //Checking whether the username and password has stored already or not
    private final boolean checkLoginInfo() {
          boolean username_set = mPreferences.contains("UserName");
          boolean password_set = mPreferences.contains("PassWord"); 
          if ( username_set || password_set ) {
                return true;
          } 
          return false;
    }

    //md5 for crypting and hash
    private static String md5(String data) {
        byte[] bdata = new byte[data.length()];
        int i;
        byte[] hash;

        for (i = 0; i < data.length(); i++)
            bdata[i] = (byte) (data.charAt(i) & 0xff);

        try {
            MessageDigest md5er = MessageDigest.getInstance("MD5");
            hash = md5er.digest(bdata);
        } catch (GeneralSecurityException e) {
            throw new RuntimeException(e);
        }

        StringBuffer r = new StringBuffer(32);
        for (i = 0; i < hash.length; i++) {
            String x = Integer.toHexString(hash[i] & 0xff);
            if (x.length() < 2)
                r.append("0");
            r.append(x);
        }
        return r.toString();
    }
}

any help would be much appreciated.
thanks!

Answer 1

When you start a thread you should save the Thread object and then call interrupt on that Thread object:

 Thread thread = new Thread(yourRunnable);
 thread.start();
 ...
 thread.interrupt();

So with the code you just added, you would do:

sessionTimer.interrupt();

Also, be aware that interrupting the thread will only cause sleep() and wait() calls to throw InterruptedException or set the thread interrupt flag. It will not stop the thread from executing. This means that you thread should use code like:

 // loop until we are interrupted
 while (!Thread.currentThread().isInterrupted()) {
    ...
    // if you use sleep or wait it should do:
    try {
       Thread.sleep(someMillis);
    } catch (InterruptedException e) {
       // if you are not quitting then you need to reset the interrupted flag
       Thread.currentThread.interrupt();
       // otherwise it is typical to quit the thread if interrupted
       return;
    }
 }

So with the code you just posted, when you are doing your sleep you should exit the run() method which will stop the thread.

                try {
                    Thread.sleep(1000);
                    Log.i("Timer", Integer.toString(i));
                } catch (InterruptedException e) {
                    // quit because we were interrupted
                    return;
                } finally {
                    finish();
                }

Also, remember that if a separate thread is calling interrupt() on the sessionTimer, then it should be marked as volatile.