android - FragmentTransaction#add(int, Fragment) not doing anything -

i have actionbaractivity (which, way, extends android.support.v4.app.fragmentactivity) , want add fragment topmost. here code:

fragmenttransaction ft = getsupportfragmentmanager().begintransaction(); notificationsfragment fragment = new notificationsfragment(); ft.add(r.id.pager, fragment).commit(); 

where:

• notificationsfragment extends android.support.v4.app.fragment
• r.id.pager id of root view (which android.support.v4.view.viewpager)

when code above runs, nothing happens. no exceptions, crashes or visual changes. nothing. i've seen fragmenttransaction not doing anything , there suggestion there telling use replace instead of add, , when tried that, pager's fragment (remember, root view pager) being displayed disappeared.

i have no idea what's going on, , i'm new android. doing wrong?

note: minimum api target in ics (15), don't need support older versions, solution involving newer apis preferred.

i have used viewpager in application , used fragmentstatepageradapter. take care of fragment management you.

you can read more viewpager here.

and fragmentstatepageradapter here.