Question

I am trying to create a thread to handle a login function that is executed when the login button is pushed, so that I can show a progressDialog.

   btnLogin.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            // Check Login


            ProgressDialog.show(Activity.this, "", "Loading...");
            new Thread(new Runnable(){
                public void run(){
                    try{
                        int duration;
                        Toast toast;
                        Context context;
                        String username = etUsername.getText().toString();
                        String password = etPassword.getText().toString();

                        JSONArray jsonArray=null;
                        password=ServerConnection.encryptPassword(password);
                        //Log.i("login hash",password);
                        jsonArray=ServerConnection.login(username, password);

                        if(jsonArray!=null) //login successful
                        {
                            context=getApplicationContext();
                            duration=Toast.LENGTH_SHORT;
                            toast=Toast.makeText(context, "Login Successful!", duration);
                            toast.show();//Shows the little pop up right at the bottom of the screen
                            Intent i = new Intent(getApplicationContext(), MapWithFriends.class);
                            startActivity(i);
                        }
                        else
                        {
                            context=getApplicationContext();
                            duration=Toast.LENGTH_SHORT;
                            toast=Toast.makeText(context, "Login Fail", duration);
                            toast.show();//Shows the little pop up right at the bottom of the screen
                            //lblResult.setText("Login failed. Username and/or password doesn't match.");
                        }
                    }catch(Exception e)
                    {
                        Log.e("tag", e.getMessage());
                    }
                    progressDialog.dismiss();
                }

            }).start();


        }
    });

However when the thread is created, it force closes. If I change back to no threads, it works fine.

Thanks

Edit:
LogCat of crash:
Can’t create handler inside thread that has not called Looper.prepare()
FATAL EXCEPTION: Thread-10
java.lang.NullPointerException
…..
would you guys need more than this?

Answer 1

You shouldn’t modify the UI from any thread except the main thread , as you do in: progressDialog.dismiss();

Consider using Handler or AsyncTask instead. And I would also recommend reading this article.