如何使用滚动视图隐藏/显示片段中的动作栏

public class MyFragment extends Fragment {
    private ScrollView scrollView;
    private ActionBar actionBar;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_layout, container, false);
        scrollView = view.findViewById(R.id.scroll_view);
        return view;
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        actionBar = ((AppCompatActivity) getActivity()).getSupportActionBar();
        scrollView.setOnScrollChangeListener(new View.OnScrollChangeListener() {
            @Override
            public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
                if (scrollY > oldScrollY) {
                    // 向下滚动，隐藏动作栏
                    actionBar.hide();
                } else if (scrollY < oldScrollY) {
                    // 向上滚动，显示动作栏
                    actionBar.show();
                }
            }
        });
    }
}