无法在 aynctask 中未调用 Looper.prepare() 异常的线程内创建处理程序答案

【问题标题】：Can't create handler inside thread that has not called Looper.prepare() Exception in aynctask无法在 aynctask 中未调用 Looper.prepare() 异常的线程内创建处理程序
【发布时间】：2018-12-10 05:21:44
【问题描述】：

我收到以下代码的此错误。我该如何解决？为什么会这样？我是 android 和 java 的新手。请解释一下。

public class UpcomingMovies extends Activity {

    ArrayList<String> moviesList = new ArrayList<String>();
    ListView moviesListView ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_upcoming_movies);
        moviesListView= (ListView) findViewById(R.id.upcomingMoviesList);

        UpcomingMovies.this.runOnUiThread(new Runnable() {
            public void run() {
                new MovieInterface().execute() ;
            }
        });
    }

    public void setUpcomingMovieList(MovieResultsPage upcomingMovies) {
        for (MovieDb result : upcomingMovies.getResults()) {
            Log.d("api", result.getTitle().toString());
            moviesList.add(result.getTitle().toString());
        }
        ArrayAdapter movieAdapter = new ArrayAdapter(getApplicationContext() , android.R.layout.simple_selectable_list_item , moviesList) ;
        moviesListView.setAdapter(movieAdapter);

    }

    class MovieInterface extends AsyncTask<String , Void , MovieResultsPage>
    {
        @Override
        protected MovieResultsPage doInBackground(String... strings) {

        TmdbMovies movies = new TmdbApi("d2e5d02fe295efc00bad8da4dc384edf").getMovies();
        MovieResultsPage upcomingMovies = movies.getUpcoming(null, 1, "IN");
        int totalpages = upcomingMovies.getTotalPages();
        Log.d("api" , "totalpages = " + Integer.toString(totalpages)) ;

        return upcomingMovies;
        }

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

【问题讨论】：

标签： java android asynchronous android-asynctask

【解决方案1】：

似乎问题是试图在不引用对象的情况下直接在new AsyncTaskCLass().execute() 上运行执行方法。

更换：

UpcomingMovies.this.runOnUiThread(new Runnable() {
            public void run() {
                new MovieInterface().execute() ;
            }
        });

作者：

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

修复它。

【讨论】：

【解决方案2】：

您只需要在 onPostExecute 中使用 runOnUiThread，在其他线程中启动一个线程有时会导致此错误，如果您必须以这种方式使用它，您必须释放 looper，但在这种情况下，我认为我的方式要容易得多：

public class UpcomingMovies extends Activity {

ArrayList<String> moviesList = new ArrayList<String>();
ListView moviesListView ;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_upcoming_movies);
    moviesListView= (ListView) findViewById(R.id.upcomingMoviesList);

    new MovieInterface().execute() ;
}

public void setUpcomingMovieList(MovieResultsPage upcomingMovies) {
    for (MovieDb result : upcomingMovies.getResults()) {
        Log.d("api", result.getTitle().toString());
        moviesList.add(result.getTitle().toString());
    }
    ArrayAdapter movieAdapter = new ArrayAdapter(getApplicationContext() , android.R.layout.simple_selectable_list_item , moviesList) ;
    moviesListView.setAdapter(movieAdapter);

}

class MovieInterface extends AsyncTask<String , Void , MovieResultsPage>
{
    @Override
    protected MovieResultsPage doInBackground(String... strings) {

    TmdbMovies movies = new TmdbApi("d2e5d02fe295efc00bad8da4dc384edf").getMovies();
    MovieResultsPage upcomingMovies = movies.getUpcoming(null, 1, "IN");
    int totalpages = upcomingMovies.getTotalPages();
    Log.d("api" , "totalpages = " + Integer.toString(totalpages)) ;

    return upcomingMovies;
    }

    @Override
    protected void onPostExecute(MovieResultsPage movieDbs) {
        super.onPostExecute(movieDbs);
        UpcomingMovies.this.runOnUiThread(new Runnable() {
            public void run() {
              setUpcomingMovieList(movieDbs);
            }
        });
    }
}
}

【讨论】：