how to fix Can't create handler inside thread that has not called Looper.prepare()

Question

Why am I getting : Can't create handler inside thread that has not called Looper.prepare() error here ?

public class MovieInterface extends AsyncTask<String, Void, MovieResultsPage> {
    public Activity activity;

    MovieInterface(Activity context) {
        this.activity = context;
    }

    public void handleUpcomingMovies() {

    }

    @Override
    protected MovieResultsPage doInBackground(String... strings) {
        TmdbMovies movies = new TmdbApi("d2e5d02fe295efc00bad8da4dc384edf").getMovies();
        MovieResultsPage upcomingMovies = movies.getUpcoming(null, 1, "IN");
        int totalpages = upcomingMovies.getTotalPages();
        return upcomingMovies;
    }


    @Override
    protected void onPostExecute(final MovieResultsPage movieDbs) {
        super.onPostExecute(movieDbs);

                ArrayList<MovieClass> mymovielist = new ArrayList<>();
                for (MovieDb movieResult : movieDbs.getResults()) {
                    mymovielist.add(new MovieClass(movieResult.getTitle(), movieResult.getOverview()));
                }

                MovieAdapter movieClassArrayAdapter = new MovieAdapter(activity, R.layout.movie_list_item, mymovielist);

                ((ListView) activity.findViewById(R.id.upcomingMoviesList)).setAdapter(movieClassArrayAdapter);

    }

Method Call :

MovieInterface movieInterface = new MovieInterface(this) ;
movieInterface.execute() ;

As other answers for similar questions have suggessted , I am not doing any UI updates inside the background method . But still am getting the error.

I'm new to android and java . How do I fix this ?

Answer 1

Call looper.prepare() in the run() method of your new thread.

A Handler can't dispatch Messages or Runnables to the Looper of a thread if it does not exist. Refer to this in the official documentation.

Answer 2

new Handler(Looper.getMainLooper())

文档中有更多详细信息。

Answer 3

onPostExecute() is invoked on the main UI thread. Try removing the runOnUiThread() call. For more details on AsyncTask see https://developer.android.com/reference/android/os/AsyncTask

Answer 4

The culprit may be one of the method calls in your doInBackground method. try running those on UIThread:

runOnUiThread(new Runnable() {
            @Override
            public void run() {
                TmdbMovies movies = new TmdbApi("d2e5d02fe295efc00bad8da4dc384edf").getMovies();
                MovieResultsPage upcomingMovies = movies.getUpcoming(null, 1, "IN");
                int totalpages = upcomingMovies.getTotalPages();
                return upcomingMovies;
            }
        });