NullPointerException while use getter

Question

Hello I have a problem with getter in my custom class, I don't know why it returns null every time. I'm setting value after response from server when it is without any errors. While I'm debugging, I see that response from server is OK and new instance of my object is created but when I try to get it in my activity there is a null. Here is couple lines of code where is a problem (in my opinion).

method from my custom class:

 public void responseFromServer(){
    showProgressDialog();
    Retrofit retrofit = new Retrofit.Builder().baseUrl(BASE_URL).addConverterFactory(GsonConverterFactory.create()).build();
    TitleInterface titleInterface = retrofit.create(TitleInterface.class);
    Call<MovieResponse> call = titleInterface.getMovie(API_KEY,movie);
    call.enqueue(new Callback<MovieResponse>() {
        @Override
        public void onResponse(Call<MovieResponse> call, Response<MovieResponse> response) {
            List<Movie> movieList =  response.body().getMovieList();
            ItemAdapter itemAdapter = new ItemAdapter(context.getApplicationContext(),generateData(movieList));
            setItemAdapter(itemAdapter);
        }

        @Override
        public void onFailure(Call<MovieResponse> call, Throwable t) {
            Toast.makeText(context, "ERROR", Toast.LENGTH_SHORT).show();
            progressDialog.dismiss();
        }
    });
}

and here is my Activity:

  @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_movie_list);

    movieListView = (ListView) findViewById(R.id.movieListView);
    String movie = getIntent().getStringExtra(TAG);

    presenter = new Presenter(this,movie);
    presenter.responseFromServer();
    item=presenter.getItemAdapter();
    movieListView.setAdapter(presenter.getItemAdapter());
    presenter.getItemAdapter().notifyDataSetChanged();
    presenter.getProgressDialog().dismiss();
}

Thanks for any help.

your call is asynchronous. the value is not set until after you try to get it. — njzk2, Sep 15 '16 at 22:04
What is the exact error message? What line causes the error? — Code-Apprentice, Sep 15 '16 at 22:09
Possible duplicate of [Unfortunately MyApp has stopped. How can I solve this?](http://stackoverflow.com/questions/23353173/unfortunately-myapp-has-stopped-how-can-i-solve-this) — Code-Apprentice, Sep 15 '16 at 22:10
@Code-Apprentice this line: item=presenter.getItemAdapter(); because is always null — FinalDestination, Sep 15 '16 at 22:12
What is always null? I assume you mean `presenter`. Where do you declare and initialize this variable? — Code-Apprentice, Sep 15 '16 at 22:15
If you are referring to the `item=presenter.getItemAdapter();` line in `onCreate()`, then there is no possible way for this to throw an NPE. You initialize `presenter` 2 lines above that. The problem must occur somewhere else. — Code-Apprentice, Sep 15 '16 at 22:16
I declared 'presenter' and 'item' before 'onCreate' as private — FinalDestination, Sep 15 '16 at 22:17
In `Presenter` class i create new object called `ItemAdapter` (in void method) , then i want to set it and after get it in my activity — FinalDestination, Sep 15 '16 at 22:19
While im debuggin when i set breakpoint on line `setItemAdapter(itemAdapter)`, variable `itemAdapter` is not null, line after is null again.. — FinalDestination, Sep 15 '16 at 22:21

score 0 · Answer 1 · answered Sep 15 '16 at 22:07

It seems like your request haven't finished when the view is created. If you want to make your call synchronous use this:

Call<MovieResponse> call = titleInterface.getMovie(API_KEY,movie);
Response<MovieResponse> responseBody = call.execute();

List<Movie> movieList =  response.body().getMovieList();

score 0 · Answer 2 · answered Sep 21 '16 at 21:47

0

You are using asynchronous calls in your app, so try to replace all necessary methods for updating UI from onCreate() to onResponse(). It should help. If you want to use Retrofit synchronous calls, the best practice for that is Loaders.

answered Sep 21 '16 at 21:47

R. Pihariev

54
5

It would be helpful if you could supply a little more info, perhaps example code? – Tibrogargan Sep 21 '16 at 23:35

NullPointerException while use getter

2 Answers2