attempt to invoke virtual method on a null Object (NullPointerException)

Question

[duplicate of a similar question]

score 0 · Accepted Answer · answered Mar 09 '17 at 18:47

Fragment's aren't exactly like activities.

You've referenced a View (movieGridView) before onViewCreated has happened, and thus it must be `null.

See here

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if(savedInstanceState != null) {
        int pos = (Integer) savedInstanceState.getSerializable("POS");
        if (!movieDataList.isEmpty()) {
            movieDataList = Arrays.asList((movieData[]) savedInstanceState.getSerializable("OLDMOVIEDATA"));
        }
       // movieGridView.setSelection(pos); // You can't do this here!
    }

}

Besides that, you do not need onCreate at all. savedInstanceState is available within onCreateView.

So, remove that method, and move the code around.

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    setHasOptionsMenu(true);

    // Added this section
    if (movieDataList == null) {
        movieDataList = new ArrayList<movieData>();
    }

    if (savedInstanceState != null) {
        index = (Integer) savedInstanceState.getSerializable("POS");

        // Not sure why you had 'not empty'
        if (movieDataList.isEmpty()) {
            movieDataList.addAll(Arrays.asList((movieData[]) savedInstanceState.getSerializable("OLDMOVIEDATA"));
        }
    } // End restore instance state


    View rootView = inflater.inflate(R.layout.movie_display_fragment, container, false);

    movieGridView = (GridView) rootView.findViewById(R.id.gv_movie_display);
    movieAdapter adapter = new movieAdapter(getActivity(),movieDataList);
    movieGridView.setAdapter(adapter);
    movieGridView.setSelection(index);

    return rootView;
}

You probably want to Bundle.putIntExtra for the "POS", but that is personal preference.

And you should also make MovieData be a Parcelable when you get a chance.

thank you very much, this fixed the NullPointerException! Great explanation. The setSelection method doesn't set the position right now though, got to fix that now! — Torben, Mar 09 '17 at 19:17
i save index in the savebundle now with putint and get it in oncreateview with getInt and then use smoothscrolltoposition but it doesn't scroll — Torben, Mar 09 '17 at 21:08
Not sure what to tell you, but that is a different issue. If you have a new question, please ask it by clicking the [Ask Question](//stackoverflow.com/questions/ask) button. — OneCricketeer, Mar 09 '17 at 21:44

score -2 · Answer 2 · answered Mar 09 '17 at 15:24

-2

initialise

private int index=0;

Since index is not initialised it will be a null value and cause the crash

answered Mar 09 '17 at 15:24

g7pro

807
6
11

2

In Java, for type int, the default value is zero, that is, 0. – Igori S Mar 09 '17 at 15:47
You can't get a NullPointerException on an `int` value – OneCricketeer Mar 09 '17 at 15:56

attempt to invoke virtual method on a null Object (NullPointerException)

2 Answers2