How to access Views again after onCreateView in Fragment?

Question

Actually I'm using Fragments with FragmentPagerAdapter, but I have the problem which is null when i tried to access views again in fragment. pageNum is null as well. I tried many ways to figure it out but it didn't work though.

FirstFragment.java

public class FirstFragment extends Fragment{
    private int pageNum;
    private TextView titleTxt;
    private LinearLayout topPan;

    public static FirstFragment newInstance(int page) {
        FirstFragment fragment = new FirstFragment();
        Bundle args = new Bundle();
        args.putInt("page", page);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        pageNum = getArguments().getInt("page", 0);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.workflow_item_layout, container, false);
        titleTxt = (TextView)    view.findViewById(R.id.title);
        topPan   = (FrameLayout) view.findViewById(R.id.top_pan);
    }

    public void setTopPanVisible(boolean isVisible) {
        topPan.setVisibility(isVisible);
    }

pageChangeListener codes

private ViewPager.OnPageChangeListener pageChangeListener = new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        }

        @Override
        public void onPageSelected(int position) {
        }

        @Override
        public void onPageScrollStateChanged(int state) {
            final int position = pager.getCurrentItem();

            if (state == ViewPager.SCROLL_STATE_IDLE) {
                final FirstFragment fragment = (FirstFragment) adapter.getItem(position);
                fragment.setTopPanVisible(true);

topPan is null when i called 'setTopPanVisible' in pageChangeListener. How can Views keep alive to have a value?

Answer 1

If you are getting a null pointer exception, then that means one of two things:

1. You are calling setTopPanVisible() before the fragment's onCreateView() method has been called.
2. Or you view.findViewById(R.id.top_pan);.

In order to fix the problem, you should figure out which one of these problems you are facing.