//Reference: https://stackoverflow.com/questions/6413700/android-proper-way-to-use-onbackpressed-with-toast
    //Accessed on 12 May 2018
    @Override
    public void onBackPressed() {
        new AlertDialog.Builder(this)
                .setMessage(R.string.are_you_sure_exit)
                .setNegativeButton(R.string.no, null)
                .setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {

                    public void onClick(DialogInterface arg0, int arg1) {
                        DefaultSettings.super.onBackPressed();
                    }
                }).create().show();
    }