java - back to previous fragment from other fragment -

i have main activity , 2 fragments on it, fragment1 call fragment2 when clicking button built in android buttons call onbackpressed function overrided in main activity , exit me app. want when click on fragment 2 onbackpressed of main activity not called , me fragment 1. button of action bar works (i think mean backstack ok).

i tried do:

getactivity().getsupportfragmentmanager().begintransaction().addtobackstack("messages"); 

on fragment 2

and tried add

getsupportfragmentmanager().popbackstack(); 

to onbackpressed() of main activity dosen't did nothing thank you

edit:

i trying      public void onbackpressed() { //      getsupportfragmentmanager().popbackstack();         android.support.v4.app.fragment fragment2 = getsupportfragmentmanager().findfragmentbytag(null);         if (fragment2 != null && fragment2.isvisible()) {             getsupportfragmentmanager().popbackstack();             return;         } 

and before show

getsupportfragmentmanager().begintransaction().addtobackstack(null).commit();         tr.show(fragment2); 

but got null on findfragment(null)

edit: checked getsupportfragmentmanager().begintransaction().mtail.fragment , saw value fragment 1 want showed, when getsupportfragmentmanager().popbackstack(); dosen't nothing.

just use below way; in activity check this

@override     public void onbackpressed() {         // todo auto-generated method stub     fragment fragment = getsupportfragmentmanager().findfragmentbytag("secondfragment");             if (fragment instanceof secondfragment) {                 // show first fragment             }else{                // finish();             }    } 

i have used findfragmentbytag, can use findfragmentbyid

i agree @minhtdh comment applicable if replace 1 on other