dataOnChange crashes fragment that has been replaced

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
        at com.darkjp.todo.MyListsFragment.sendSomeToThatRecyclerViewBiatch(MyListsFragment.java:93)
        at com.darkjp.todo.MyListsFragment.access$000(MyListsFragment.java:24)
        at com.darkjp.todo.MyListsFragment$1.onDataChange(MyListsFragment.java:61)

and the checkbox causing the crash:

isDoneCheckBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
    @Override
    public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
        final DatabaseReference mDone = database.getReference("tasksList/" + taskListIndex).child("task/" + taskIndex);
        mDone.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                Task updateTask = new Task();
                if (snapshot.child("creator").getValue() != null) {
                    if (snapshot.child("creator").getValue().toString().equals(""))
                        updateTask.setCreator("no creator found");
                    updateTask.setCreator(snapshot.child("creator").getValue().toString());
                }
                if (snapshot.child("title").getValue() != null && !snapshot.child("title").getValue().toString().equals(""))
                    updateTask.setTitle(snapshot.child("title").getValue().toString());
                if (snapshot.child("description").getValue() != null && !snapshot.child("description").getValue().toString().equals(""))
                    updateTask.setDescription(snapshot.child("description").getValue().toString());
                if (snapshot.child("done").getValue() != null)
                    updateTask.setDone(isDoneCheckBox.isChecked());
                mDone.setValue(updateTask);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {

            }
        });
    }
});

The recyclerView received a changed, which is nornam, but the recyclerView is in a fragment I suppose "onPause". Fragment has been replaced (dynamic frameLayout), and should be on its way to destruction or get back from the backstack, I guess.
The onChange seems to get it crashes the app.
I'm studying the onPause/onResume fragments behavior to see how I could manage a dataOnChange when its "sleeping" but I can't see no clue.

If I got the problem well: i try to find a recyclerView that does not exist in the actual fragment (and can't be reached while onPause(), OnResume()...).
I can't figure out why that fragment is called (when another one would have been more pertinent. The one i'm thinking of is called/instantiated by myListFragment... i guess a parent/children flow is behind that mystery.

Ok...
Was not a lifecycle one.

i was doing a getView() to get the "R.id.xxxxxx" recyclerView. And it was wrong so it launched once but could not be resume. I just, now, get the recyclerView from a "classic"

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        view = inflater.inflate(R.layout.fragment_my_lists, container, false);
        myRecycler = view.findViewById(R.id.myRecycler);       
}

i was doing a

myRecycler = this.getView.findViewById(R.id.myRecycler);