findViewById in Fragment

Use getView() or the View parameter from implementing the onViewCreated method. It returns the root view for the fragment (the one returned by onCreateView() method). With this you can call findViewById().

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    ImageView imageView = (ImageView) getView().findViewById(R.id.foo);
    // or  (ImageView) view.findViewById(R.id.foo); 

As getView() works only after onCreateView(), you can’t use it inside onCreate() or onCreateView() methods of the fragment .