I can’t call an Activity through a Fragment

Question

First of all lose by mistakes (keyboard bugle).

Well I’m trying to call an Activity through the code below, this code is in my Mainactivity.java. I created the Fragments to be called through the Drawer Menu and it works perfectly. My goal is to be able to call an Activity directly from this menu but it doesn’t work, the app compiles runs just right but when I touch the desired item (about) the app hangs.

I’m using this code to try to call Activitysobre.

Intent iSobre = new Intent(this, ActivitySobre.class);
startActivity(iSobre);

I have already searched and found codes like getActivity(), however that does not work.

Mainactivity.java

private void displaySelectedScreen(int id){
    android.support.v4.app.Fragment fragment = null;

    switch (id){
        case R.id.nav_home:
            fragment = new FragmentHome();
            break;
        case R.id.nav_notificacao:
            fragment = new FragmentNotificacao();
            break;
        case R.id.nav_favorito:
            fragment = new FragmentFavoritos();
            break;
        case R.id.nav_minhaconta:
            fragment = new FragmentMinhaConta();
            break;
        case R.id.nav_share:
            fragment = new FragmentSobre();
            break;
        case R.id.item_sobre:
            Intent iSobre = new Intent(this, ActivitySobre.class);
            startActivity(iSobre);
            //fragment = new FragmentSobre();
            break;
    }

    if(fragment != null){
        android.support.v4.app.FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.content_main, fragment);
        ft.commit();
    }

Does anyone have any idea how to fix this? Since the Spring.