Reference FragmentActivity to external Interface

I want to call a function in a fragment from a class. How do i attach FragmentActivity to External Interface like i attach Activities

Currently for Activity, the class contains

public interface externalInterface {
    public void gotoNext();
}

public void setActivity(externalInterface activity) {
    parentActivity = activity;
}

and i called

parentActivity.gotoNext();

Activity has

@Override
public void gotoNext() {
    //Do something
}

Similarly i need to call gotoNext() function in a fragment from the same class.

If the function you want to call is already in the Activity then you can do something like the code below and it will work -

The key is, in the Fragment you have a method called getActivity() which you can use to access methods in your activity.

public interface ExternalInterface {
  public void gotoNext();
}

public MyActivity implments ExternalInterface {
 public void gotoNext(){
 //Do something here
 }
}

In your Fragment, you can call

 public MyFragment extends Fragment{

@Override
public void onCreateView(....){
 ((ExternalInterface )getActivity()).gotoNext();
 }
}