Handle login event using MyApi Request factory, a "custom" listener and an error listener. Part of http://develop-for-android.blogspot.com.es/2014/01/using-volley-in-your-application_31.html

AuthenticatorActivity.java

// ...

	/**
	 * Handles onClick event on the Submit button. Sends username/password to
	 * the server for authentication.
	 * 
	 * @param view The Submit button for which this method is invoked
	 */
	public void handleLogin(View view) {
		if(((EditText) findViewById(R.id.username)).getText() == null ||
				((EditText) findViewById(R.id.username)).getText().toString().
				trim().length()
				< 1) {
			Toast.makeText(this, "Please enter a Username", 
					Toast.LENGTH_LONG).show();
			return;
		}

		if(((EditText) findViewById(R.id.password)).getText() == null ||
				((EditText) findViewById(R.id.password)).getText().toString().
				trim().length()
				< 1) {
			Toast.makeText(this, "Please enter a Password", 
					Toast.LENGTH_LONG).show();
			return;
		}

		if (mRequestNewAccount) {
			mUsername = mUsernameEdit.getText().toString();
		}

		mPassword = mPasswordEdit.getText().toString();
		showProgress();
		
		// Start authenticating...
		MyApi api  = new MyApi(this);
		api.newLoginRequest(
		  mUsername, 
		  mPassword, 
		  this.loginSuccessfulListener(), 
		  this.loginFailedListener()
		  );
	}

	private Response.Listener<LoginResponse> loginSuccessfulListener() {
		return new Response.Listener<LoginResponse> () {
			/**
			 * @param loginResponse DAO object with the session token
			 */
			@Override
			public void onResponse(LoginResponse loginResponse) {

				// Provide feedback - hide the mProgress dialog
				dismissProgress();
				
				// execute the business logic to actually create a user session
				finishLogin(loginResponse.getSessionToken());
			}
		};
	}

	private Response.ErrorListener loginFailedListener() {
		return new Response.ErrorListener () {

			@Override
			public void onErrorResponse(VolleyError error) {
				// execute business logic related to a failed login attempt
				// ...

				// Provide feedback 
				dismissProgress();
				new AlertDialog.Builder(AuthenticatorActivity.this).
					setTitle(R.string.login_failed).
					setNeutralButton(R.string.ok, null).
					show();
			}
		};
	}

//	...