onResponse的改造没有设置字段

Question

我非常感兴趣为什么onResponse setter的方法效果不好。这是来自我的自定义类的方法，它负责从服务器获取响应。我注意到我想让它像我的代码一样异步。

 public void setListItem(ArrayList<Item> listItem) {
    this.listItem = listItem;
}
 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();
            setListItem(generateData(movieList));
    }
        @Override
        public void onFailure(Call<MovieResponse> call, Throwable t) {
            Toast.makeText(context, "ERROR", Toast.LENGTH_SHORT).show();
            progressDialog.dismiss();
        }
    });
}
 private ArrayList<Item> generateData(List<Movie> list){
   listItem =new ArrayList<Item>();

    for(int i=0;i<list.size();i++){
        String title = list.get(i).getOriginalTitle();
        String overview = list.get(i).getOverview();
        String date = list.get(i).getReleaseDate();
        float rate = list.get(i).getVoteAverage();
        listItem.add(new Item(title,overview,date,rate));
    }
    return listItem;
}

这种我尝试在Activity中获取变量的方式，每次调试时都是null。

presenter = new Presenter(this,movie);
presenter.responseFromServer();
ArrayList<Item> item = presenter.getListItem();