Why is it necessary to implement OnFragmentInteractionListener when setting up a fragment?

I followed the official documentation: https://developer.android.com/guide/components/fragments#Creating. It provides the steps to set up a fragment.

First, create the fragment class (`extends Fragment')

Then create its layout (and, in fragment class' OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState), return one of the View' of this layout usinginflate`)

OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)

View' of this layout using

Choose an activity that will use this fragment. This activity must extends FragmentActivity and in order to use the fragment, it will contain calls to FragmentManager's methods, FragmentTransaction'smethods, etc.

extends FragmentActivity

FragmentManager

FragmentTransaction

However, doing this results in a "fatal exception":

java.lang.lang.lang.RuntimeException: com.example...TheActivity@efebfcf must implement OnFragmentInteractionListener

Questions

Why doesn't the documentation mention this problem?

In TheActivity (which uses the fragment TheFragment), I implemented TheFragment.OnFragmentInteractionListener (yes, TheFragment.OnFr...!). It's weird, isn't it? In addition, this listener provides this method: onFragmentInteraction(Uri uri) but what is it supposed to contain?

TheActivity

TheFragment

TheFragment.OnFragmentInteractionListener

TheFragment.OnFr...

onFragmentInteraction(Uri uri)

1 Answer
1

I'm pretty sure in the Fragment's onAttach method, it will say that the parent activity must implement the OnFragmentInteractionListener. This is to facilitate Fragment to Activity communication.

onAttach

OnFragmentInteractionListener

This is not required and the check in onAttach can be removed. In fact if you are not doing anything in the onAttach method then the whole method can be removed from the Fragment

onAttach

onAttach

Fragment

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