Call an activity method from a fragment

From fragment to activty:

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

From activity to fragment:

FragmentManager fm = getSupportFragmentManager();

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

If you added fragment via code and used a tag string when you added your fragment, use findFragmentByTag instead:

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