public void showFragment(String fragmentName) {

        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();

        Fragment curFragmnet = fm.findFragmentById(R.id.fragmentContainer);

        if(curFragmnet == null) {
            switch(fragmentName) {
                case "FragmentOne":
                    ft.add(R.id.fragmentContainer, new FragmentOne()).commit();
                    break;
                case "FragmentTwo":
                    ft.add(R.id.fragmentContainer, new FragmentTwo()).commit();
                    break;
                case "FragmentThree":
                    ft.add(R.id.fragmentContainer, new FragmentThree()).commit();
                    break;
            }
        } else {
            switch(fragmentName) {
                case "FragmentOne":
                    ft.replace(R.id.fragmentContainer, new FragmentOne()).commit();
                    break;
                case "FragmentTwo":
                    ft.replace(R.id.fragmentContainer, new FragmentTwo()).commit();
                    break;
                case "FragmentThree":
                    ft.replace(R.id.fragmentContainer, new FragmentThree()).commit();
                    break;
            }
        }
    }