Call an activity method from a fragment

((YourActivityClassName)getActivity()).yourPublicMethod();

FragmentManager fm = getSupportFragmentManager();

//if you added fragment via layout xml
YourFragmentClass fragment = (YourFragmentClass)fm.findFragmentById(R.id.your_fragment_id);
fragment.yourPublicMethod();

tag

findFragmentByTag

YourFragmentClass fragment = (YourFragmentClass)fm.findFragmentByTag("yourTag");