Java AsyncTask不返回任何值

我有一个适配器类和一个模型类，它们工作得很好。我认为内部AsyncTask有问题，我无法将json的结果显示在主活动上。请帮忙

我还包括了json响应的外观

public class MainActivity extends AppCompatActivity {

public ArrayList<NetworkUtils> moviesList = new ArrayList<>();
private RecyclerView mRecyclerView;
private MoviesAdapter mMoviesAdapter;

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

    mRecyclerView = (RecyclerView) findViewById(R.id.rv_main_activity);
    mRecyclerView.setHasFixedSize(true);
    mRecyclerView.setLayoutManager(new GridLayoutManager(this, 2));

    mMoviesAdapter = new MoviesAdapter(this);

    mRecyclerView.setAdapter(mMoviesAdapter);
    mMoviesAdapter.setMoviesList(moviesList);

    new FetchMoviesTask().execute("my url goes here");
}

    @Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

public class FetchMoviesTask extends AsyncTask<String, Void, List<NetworkUtils>> {

    @Override
    public List<NetworkUtils> doInBackground(String... params) {
        HttpURLConnection connection = null;
        BufferedReader reader = null;
        String json;

        try {
            URL url = new URL(params[0]);
            connection = (HttpURLConnection) url.openConnection();
            connection.connect();

            InputStream stream = connection.getInputStream();
            StringBuffer buffer = new StringBuffer();
            reader = new BufferedReader(new InputStreamReader(stream));


            json = buffer.toString(); 

            JSONObject parentObject = new JSONObject(json); 
            JSONArray parentArray = parentObject.getJSONArray("results");


            for (int i = 0; i < parentArray.length(); i++) {
                JSONObject finalObject = parentArray.getJSONObject(i); 
                NetworkUtils tmdbMovies = new NetworkUtils();
                tmdbMovies.setTitle(finalObject.getString("title"));

                moviesList.add(tmdbMovies);
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return moviesList;
    }

    @Override
    public void onPostExecute(List<NetworkUtils> moviesList) {
        super.onPostExecute(moviesList);
    }
}}

适配器类

public class MoviesAdapter extends 
RecyclerView.Adapter<MoviesAdapter.MoviesViewHolder> {

private List<NetworkUtils> moviesList = new ArrayList<>();
private Context context;

public class MoviesViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

    private TextView titleTextView;

    public MoviesViewHolder(View itemView) {
        super(itemView);
        titleTextView = (TextView) itemView.findViewById(R.id.movie_title);
        itemView.setOnClickListener(this);
    }

    @Override
    public void onClick(View itemView) {
        Context context = itemView.getContext();
        Intent showMovieIntent = new Intent(context, MainActivity.class); 
        context.startActivity(showMovieIntent);
    }
}
public MoviesAdapter(List<NetworkUtils> moviesList) {
    this.moviesList = moviesList;
}
public MoviesAdapter(MainActivity mainActivity) {
}

@Override
public MoviesViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.image_layout, parent, false);
    return new MoviesViewHolder(view);
}

@Override
public void onBindViewHolder(MoviesViewHolder holder, int position) {
    NetworkUtils movies = moviesList.get(position);
    TextView mTextView = holder.titleTextView;
    mTextView.setText(movies.getTitle());
}

@Override
public int getItemCount() {
    if (moviesList == null)
        return 0;
        return moviesList.size();
}
public void setMoviesList(ArrayList<NetworkUtils> mMoviesList) {
    moviesList = mMoviesList;
    notifyDataSetChanged();
}
}

公共类MoviesAdapter扩展
RecyclerView.适配器{
private List moviesList=new ArrayList（）；
私人语境；
公共类MoviesViewHolder扩展了RecyclerView.ViewHolder实现了View.OnClickListener{
私有文本视图titleTextView；
公共电影视图持有者（视图项视图）{
超级（项目视图）；
titleTextView=（TextView）itemView.findViewById（R.id.movie\u title）；
setOnClickListener（这个）；
}
@凌驾
公共void onClick（视图项视图）{
Context=itemView.getContext（）；
意图showMovieIntent=新意图（上下文，MainActivity.class）；
背景。startActivity（showMovieIntent）；
}
}
公共MoviesAdapter（列表moviesList）{
this.moviesList=moviesList；
}
公共电影适配器（MainActivity MainActivity）{
}
@凌驾
public MoviesViewHolder onCreateViewHolder（视图组父级，int-viewType）{
View=LayoutInflater.from（parent.getContext（））
.充气（R.layout.image_layout，父级，false）；
返回新的MoviesViewHolder（视图）；
}
@凌驾
BindViewHolder上的公共无效（MoviesViewHolder，内部位置）{
NetworkUtils movies=moviesList.get（位置）；
text视图mTextView=holder.titleTextView；
mTextView.setText（movies.getTitle（））；
}
@凌驾
public int getItemCount（）{
if（moviesList==null）
返回0；
返回moviesList.size（）；
}
public void setMoviesList（数组列表mMoviesList）{
moviesList=mMoviesList；
notifyDataSetChanged（）；
}
}

您希望显示什么以及如何显示？在

onPostExecute（）

中调用适配器上的

notifyDataSetChanged（）

会有帮助。我需要在gridview中显示所有标题的名称。同时显示适配器代码。我编辑了我的问题以包含适配器类。您不应该在后台线程中更新数据源，请参见此处：，创建一个新列表，该列表将被传递到

onPostExecute（）

，并使用

addAll（）

方法更新

moviesList

数据源，然后在适配器上调用

notifyDataSetChanged（）

。

public class MoviesAdapter extends 
RecyclerView.Adapter<MoviesAdapter.MoviesViewHolder> {

private List<NetworkUtils> moviesList = new ArrayList<>();
private Context context;

public class MoviesViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

    private TextView titleTextView;

    public MoviesViewHolder(View itemView) {
        super(itemView);
        titleTextView = (TextView) itemView.findViewById(R.id.movie_title);
        itemView.setOnClickListener(this);
    }

    @Override
    public void onClick(View itemView) {
        Context context = itemView.getContext();
        Intent showMovieIntent = new Intent(context, MainActivity.class); 
        context.startActivity(showMovieIntent);
    }
}
public MoviesAdapter(List<NetworkUtils> moviesList) {
    this.moviesList = moviesList;
}
public MoviesAdapter(MainActivity mainActivity) {
}

@Override
public MoviesViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.image_layout, parent, false);
    return new MoviesViewHolder(view);
}

@Override
public void onBindViewHolder(MoviesViewHolder holder, int position) {
    NetworkUtils movies = moviesList.get(position);
    TextView mTextView = holder.titleTextView;
    mTextView.setText(movies.getTitle());
}

@Override
public int getItemCount() {
    if (moviesList == null)
        return 0;
        return moviesList.size();
}
public void setMoviesList(ArrayList<NetworkUtils> mMoviesList) {
    moviesList = mMoviesList;
    notifyDataSetChanged();
}
}